Mission Statement

Mission

Our Mission is to provide our customers with high quality electricity and water services, whilst creating value for our shareholders.

Objectives

Our objectives are to:Efficiently meet our obligation to supply Qatars need for electricity and water. Operate on a commercial basis. Comply with local and international health, safety, and environmental standards. Maximize the employment of capable Qatari nationals and develop them to the competence level of employees in leading international companies.

History

IntroductionQatar General Electricity & Water Corporation,was established in July, 2000 further to the Emiri Law number 10, to regulate and maintain supply of Electricity & Water to customers.Since inception, Kahramaa has operated as an independent corporation on a commercial basis with a total capital of four billion Qatari Riyals. Kahramaa was mandated with several responsibilities and commitments, some of which are:

The right to own, construct, operate and maintain electricity generation stations, water desalination plants, electricity transmission and water distribution networks.

Set up of infrastructure & network development plans and programs. Lay out regulations, standards and codes of practices which pertain to

provision of electricity and water supplies to various buildings and establishments as well as review of their implementations.

Provide consultancies & services related to its operations.

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Board Of DirectorsKahramaa board of directors comprises of Chairman, vice-chairman and several members. The board is appointed for a four-year office term subject to renewal by an Emiri decree, based on Kahramaa's law- article 7.

a. JurisdictionsThe Board of directors at Kahramaa is granted extensive authorities to achieve the corporation's goals mainly, the setting, and implementation and follows up of general policies, plans, programs and projects.The board main responsibilities are the approval of corporation’s organizational structure, endorsement of the financial, administrative and technical internal rules and regulations, employees policies and regulations, as well as approving the corporation investment plans, its annual budgets and closing fiscal year and approves loans with the Government and other parties, in addition to review of the operational and strategic performance.

b. The Financial ResourcesThe main financial resources of Kahramaa is the annual allocated funds from the state (government), services fees and revenues, the return of its capital investments on its assets as well as the value of its shares and loans extendedtoothers.

The Electricity SectorThe Electricity transmission networks consist of approximately 100 primary High Voltage sub-stations with total 660 km of overhead lines supported by 600 km of underground cables across the country. The network is coupled with 6500 low and medium voltage sub-stations (11kv) and more than 4500km of cable lines.The National Control Center (NCC), which contains state-of-art technologies, manages all network demand and data acquisition from generation plants and primarysub-stations.

Electricity DemandDemand on the electrical energy in Qatar has increased over the past fifty years; the maximum load over the network during the period from 1988 to 2003 has risen from 941 Megawatt to 2312 Megawatts (MW). It has reached 2520MWin2004.

The Water SectorThe water network in Qatar has been expanded extensively in recent

years, the growth of urban areas; industry and agriculture has lead to the increase in the length of the water network to 3622 km and expansion in the number of storage reservoirs to 23 with a total capacity of 259 million gallons of water a day.

DISTRIBUTION SYSTEM ,KAHRAMAA,QATAR

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Primary distribution voltage – 11 KV, Frequency – 50 Hz.

System Voltege variation allowed – 10.7 KV to 11.3 KV

HT network – 3 phase 3 wire System

LT network - 3 phase 4 wire System

GENERAL OVER VIEW

Kahramaa distribution Network consists of about 10000 Nos substation. They

are either Indoor type or Out door type.

Max demand - 3025 (27.06.2006) till date

The domestic consumption is more predominant in the system and domestic

load contributes major portion of the total demand. Remaining are industrial

and they contribute very less, near about 15% of the load (approx. 450

mw).Seasonal variations are predominant because of the extreme climatic

conditions. In summer, hot season begins from May – September, the

demand reaches its maximum value But in winter season, (Nov- Feb), the

demand reaches its minimum value.

In summer season demand is about 3000 MW

In winter season demand is about 1000 MW

But the Repaid economical & industrial development brings, Qatar power

sector a demand growth of about10% every year.

KAHRAMAA'S distribution Network consists of about 10000 Nos substation.

They are either Indoor type or Out door type. Distribution network is fed from

Primary substations ( 92 Nos ) and mostly they are 66 /11 KV substation's

with two incoming transformers (Rating 25/36/40MVA ). Some 33 / 11 KV

sabstation's are also provided for feeding the 11 KV distributions network.

Under ground cables are widely used to meet the urban load and rural

network is constructed by using OH/L. There are indoor and outdoor

substations are provided depending upon the load requirement and

operational flexibility. These substations are also helps to achieve

continious,stable and reliable supply thruogh out the state of Qatar. The

indoor & outdoor substations are provided with different sources to feed the

LT transformers. Closed Ring, Ring off ( Normaly opened point's – NOP ) and

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Radial feedings are used in the distribution network depending upon the

nature of the Consunar load.

MAIN NETWORK ELEMENTS1) Primary Substation

2) Indoor Substation

3) Outdoor Substation

4) Under ground cables

5) Over head lines - OH/L.

1) Primary Substation

Main incoming supply to the Primary Substation is fed from 66

KV system. Two main incoming transformers are generally provided to feed

the 11 KV Distribution system. 11 KV Bus is provided with a Bus

Coupler(A120) for oparational flexibility and is normally in closed condition..

All Switchgear panels for incoming feeders,transformers and outgoing feeders

are equiped with Circuit Breakers,Isolators and Earth switches. Current

transformer and Voltage transformers are also provided in each circuit for

protection & metering. Earthing transformers are provided for stable neutral

and for station supply. Circuit breakers are of either VCB/SF6 / OCB types are

used.DC System is 110 V DC with Battery and Charger. The primary

substatoin are well equipped with Control panel,protection panel,Switch gear

panel and Axilliary facilities. Local and remote control is possible for all

panels by selecting the selection switch on panels.RTCC with AVR is also

provided for meeting on load automatic tap changing.

Operation and Maintanance

Maintenance of Primary Substation is always under the control

of transmission wing. All switching operations on 11 KV outgoing feeders are

done by distribution engineer. But switching operation on HV , LV side of

Primary transformers (Incomers) and Bus section Breakers are done by the

transmission wing.

Safety Measures

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All primary Substation are well protected from fire hazards.Co2

fire extinguisher system (auotamatic) is provided in Primary substation where

Cicuit Breaker is OCB.But in new phase v Primary’s are commissioned with

SF6 as insulation medium.

Operation Control

A selector switch is provided in each panel to control the

operation of breakers from either locally or remotely (Grid). Normally the

Selector switches are in Grid position where Out going feeders are in DCC

control and Incomers and Bus Coupler are in NCC control.A Senior

Authorised person can change the Selector switch position for work only with

the consent of Contrl Engineers of NCC/DCC.

2) Indoor SubstationAll Indoor Substations are well equipped with Switchgear panels

with Circuit Breakers,isolating & eathing facility,control and protection circuitry

and metering facility for the smooth operation and control of feeder and Local

distribution transformers. All Feeders and L/Tx are connected to the common

bus of the Indoor substation through the respective circuit breaker. DC

system available is 30V DC with Battery and Charger.Station LT supply for

station lighting and Battery Charger is taken from L/Tx. All of the switchgeer

panels, L/Tx and Communication systems are protected inside a room.

Circuit Breakers used

1) OCB- Oil Circuit Breaker –Oil (Medium)- Vertical isolation

Types available are

Ray RlleSouth WalesBrush GEC2) VCB- Vaccum circuit Breaker- Vaccum(medium) – Horizontal isolation

Types available are

TAMCOAL-AHILIYAEPE, Ray Rolle and Ranhil

Distribution Transformers

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Local & Remote transformer are provided to cater the

distribution load. Available ratings are 500 KVA, 800 KVA,1000 KVA ,1250

KVA & 1600 KVA. The HT cable length more than 15 metre is considered as

R/TX

Control and Protection

Control and protection circuitry is provided with the Switchgear panel

for the control and protection of Feeders and L/Tx’s.Local control facility is

only available for CB.

Metering

Ammeters are provided in each circuit to measure the load current

Status indicators are provided for circuit Breakers

DC voltmeter is provided to measure the DC voltage.

Operation and Maintanance

Presently no remote control is possible. Local operation &

Maintenance is always done by the Field engineers(Senior Authorised

Person) of Distribution Department with proper consent from System Control

Engineer on duty.

3) Out Door Substations

In Outdoor substations, Main Switches and Transformer

switches along with Earthing facility is provided for oparational, maintanance

and construction activities. The main switches are intended to break/make the

load current manually.Protection and control circuits are not assosiated with

the main switches inorder to protect the curcuit under overload / fault

condition.But the transformer circuit is provided with Oil Fuse Switches(OFS)/

TX Switch with Time lag Fuse(TLF) to protect the transformer from overload

and fault condition. The automatic tripping of the TX Switch is depend upon

the rating of fuse provided in the circuit.The fuse rating is selected as per the

transformer capacity.If the load current is more than the rated value of fuse.

Then the transformer switch automaticaly trips the circuit and protect the

transformer. Other than OFS / TLF,there is no protection available in Out door

S/S.Metering circuits are also absent in the outdoor substation except the

Ammeter with load current and Maximam Demand indicator provided in the

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Feeder Pillar.Status Indicators are provided for Main switches,earth switches

and transformer switches.Earth fault indicators and Gas pressure indicators

are also provided in outdoor substation.

Main Components of Out door S/S

Main Switches for Feeders

Earth Switches for Feeders and Transformers

Transformer Switches (OFS & TXS)

Current Transformers provided for EFI

Local Transformers - 11KV/433 V

Bolt on Feeder Pillar (BOFP) /Free Standing Feeder Pillar (FSFP)

HT and MV cables.

Earth fault Indicators

Gas Pressure Indicators (only in SF6 Outdoor s/s)

Classification according to Insulation Medium

In outdoor s/s, all feeder switches and TX switches are provided with either oil

or SF6 Gas as insulation medium for breaking/making load current.

Oil Switches:- Oil is used as insulation medium for breaking /making the load

current. All switches are rated for breaking/ making load current and not

intended to break /make the fault current.But for transformer circuit Oil Fuse

Switches (OFS) are parovided with Oil Fuses.In OFS a mechanical inter

locked over load protection is provided for tripping the transformer circuit

under over load condition..If any of the fuses blows out, a mechanical

interlocking arrangement by means of a Plunger and latch opens the contacts

of the OFS. Different types of Oil Fuse Switches are:-

Long Crawford – Old version, operation is risky, if any abnormalities found,

avoid the switching. Then other remote switches can be

used for operational purposes.

W LucyYorkshireTiger

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SF6 Switches:- SF6 gas is used as insulation medium in new outdoor s/s's

where the breaking / making of load current is through the SF6 gas insulation

medium. In SF6 O/D substations, for transformer Switches are normally

provided with the Time Lag Fuses (TLF) for tripping the circuit Breaker (TXS)

on abnormal condition. These fuses are provided in the secondary circuit of

the CT across a shunt coil. Normal condition the current will flow through the

TLF( low impedence path) Any abnormality comes the fuse will blown out and

it will results the flow of current through the shunt coil (high impedence trip

coil) which in turn trips the circuit breaker.Different types used are :-

TamcoMerlin GerinABB W Lucy

Fuse rating for different rating transformer

Oil Fuse rating available - 40A,63A,70A& 90A

Standard TLF Rating available – 5A,7.5A,10A,12.5A &15A

Voltage Transformer

Voltage Transformers (VT) are provided for metering, protection and

synchrocheck. VT is always part of Cable and is provided in all Primary

substation and in some Indoor Substation.In Primary all Feeders ,Incomers

and Bus sections are equipped with VT. VT's are consider as part of the

cable and hence VT isolation is compulsory while doing any type of injection

test like HV Pressure test.Before VT isolation, confirm the cable is dead and

isolated at both ends.

Current Transformer

Different Class CTs are used in Primary as well as in Indoor

Substation for protection & metering. CT's are also provided in O/D

substations in the Earth Fault Indicator circuit for indicating passage of the

Earth fault. In SF6 -O/D Substation , CT is required in the TLF protection

circuitry.

Types of Out Door substation

Ring Main Unit (RMU)

Semi Extensible RMU

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Extensible RMU

Out Door Substation with feeder switches &TX Switch

Out Door Switching station

Package Substation

Ring Main Unit(RMU)

A single unit with two feeder switches and one T-off

transformer switch. Oil and SF6 switches are available. Only one Transformer

circuit is available .Normally Transformer is connected to the T-off circuit and

two feeder switches provided on both sides.

Semi Extensible RMU

The outdoor substation with one RMU unit and which has a

provision to extend its Bus bar towards one side to add more circuits (Feeder

Switches/Tx switches) depending upon the Bus Bar current carrying

capacity.The extensible side of the RMU is provided with an Endcap.

Extensible RMU

The outdoor substation with one RMU unit and which has a provision to

extend its Bus bar towards both sides to add more circuits (Feeder

Switches/Tx switches) depending upon the Bus bar current carrying

capacity.Endcaps provided on both sides.

Extensible Out door Substation

In this out Door substations, individual switches are provided for

transformer and feeder circuit in a common Bus Bar and has a provision to

extend its Bus Bar towards both sides. Endcaps provided on both sides. No

RMU unit is available.

Out door Switching Station

Transformer switches and RMU units are absent in this type.

Feeder switches provided for switching and operational flexibility and

connected in a common busbar with extensible feature.

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Package Substation

In package substation where the RMU unit and FeederPillar

units are attached (Bolted) to the transformer and formed a single package

unit. HV and MV cables are not required for transformer.

Main Switch,Transformer Switch & Earth Switch

Main Switches are intended to making /breaking load current only and

there is no associated protection circuitry. These switches are not

designed to break / make fault current.

Status indication windows are available for Main swtches,Earth

switches and TXS to indicate the current status of operation.

Main Switch Closed condition - "ON" with red background

TX Switch Closed condition - "ON" with red background

Earth Switch Closed condition - "ON" with yellow background

Earth Switch /Main Switch /TX Switch - Opened condition -

"OFF" with green background

TX Switches are provided with Oil Fuse/ TLF for tripping the circuit

under overload / abnormal condition.

Inter locking

1) Inter locking facility is provided between Earth Switch ON and Main

Switch ON condition.

2) Inter locking facility is provided between Earth Switch ON and TX

Switch ON condition.

3) No inter locking facility is provided between Earth Switch OFF and Main

Switch /Transformer Switch OFF condition.

4) Opening/Closing of test plug is allowed only when the earth switch of

respective circuit is in ON condition. In SF6 RMU , the TLF compartment

also having the inter locking facility of this type.

5) Safety and normal operational locks are also provided to all switches.

Earth Fault Indicators (EFI)

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Earth Fault Indicators (EFI) are provided in Out Door substations for

indicating the passage of fault current. EFI is normaly provided in left hand

side of RMU. EFI is actuated by a CT secondary current during earth fault.

The CT is wrapped around the feeder circuit cable. Manual reset and Auoto

reset types EFI’s are available.

Manual type –Manual reset is required after the Flag ON condition due to fault

Auto type - LT supply is provided to EFI and it automatically reset the Flag

due to the fault after a delayed time period when supply resumed.

Gas Pressure Indicator for SF6 RMU

The Gas Pressure Indicator reading should be in the green zone for the safe

oparation of SF6 RMU.

Filling Pressure at 20 degree cent.- 0.4 BARG

Minimum oparating Pressure - 0.05 BARG

Red zone - operation of RMU is not allowed.

Green zone - Operation is allowed

If it is in red zone, refilling is required for further operation and is allowed only

with PTW.

HV and MV cable of Distribution Transformer

11KV HT Single run 3 core cable connect the TX Switch to the Transformer

Primary winding. MV cable Seven run single core (Double run for phases and

Single run for neutral) connect the Transformer Secondary to the MV feeder

piller.

Feeder Pillar

Bolt on Feeder Pillar(BOFP) – 4 LT Out going Cables

Free Standing Feeder Pillar (FSFP)- 6 LT Cable Out going

MV panel could be mounted in two ways:-

1. As an attachement (Bolted) to the Transformer Secondary without MV

cables is called Bolt on Feeder Pillar(BOFP)

2. As a separate unit anchored to the ground and secondary of Transformer is

connected with MV cable called Free Standing Feeder Pillar(FSFP)

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Special free standing feeder pillar – Consumer FSFP and Special consumer

panel is available. 4 or 5 LT Out going Cables + Cable for one separate

consumer panel.

MV Panel - Components

MV link (R,Y,B &N)

Ammeter with Maximum Demand Indicating feature

Bus Bar (R,Y,B and Neutral)

MV side cut out fuses ( 100A,200A,315 A)

MV outgoing Cable (4 or 6 circuits)

Eatrhing Bus

Current Transformer

In Feeder Pillar MV links are provided for LT Outgoing Cables (3 Phase 4 wire

with separate Earth wire ) HRC fuses are provided in LT cable for overload

protection rating depends on the load current. In some consumer MV panel is

available with ACB and REF protection.

Maximum Demand Indicator

Ammeter is provided in MV panel with two needles. One is for the real

time load current measurement and the other one is for all time Meximum

Demand.This indication is more usefull tripping/fault analysis.

LT Transformer – ( 11 / 0.433 KV ) Dyn 11 Off load tap changing feature – 1 to 5 tap possisions- nominal tap is 3

Local TX - upto 15 mtr

Remote TX - above 15 mtr

Available Transformer ratings - 100, 200,300,500,800,1000,1250,1600 KVA

Under Ground Cables XLPE - recent standard( ax,bx,cx,dx,ex &gx)

PILC - Old (a,b,c,d)

HT – 3 phase 3core cable , MV – 3 phases and Neutral

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Overhead Lines (OH/L)Rural areas are electrified by means of OH/L .ACSR and Copper conductors

areavailable

HT - 3 phase 3 wire system and seperate Earth wire is provided

- for 10 poles one Earth pit is provided

- Separate earth pits are provided for LA,Pole Box and PMT

LT - 3 phase 4 wire System

- Cut out fuses are provided depending upon the load.

Safety during shut down

The working section should be dead , isolate & Earth at both ends

before doing any work

Test OH/L line before starting work by using an HV Tester for

confirmation

If the OH/L found Dead,apply Portable Earth at the point of work

Always instruct the workforce to wear

Safety Belt

Safety Shoe

Helmet

Gloves

Field Engineer should collect the original copy of safety document

(PTW) signed by the competent person

OHL work should be stopped immediately when the atmosphere

becomes cloudy and chances of lightning and thunder showers are

likely to occure.

Main components

AB Switch (S)

Lightning arrester (LA)

Ploe Mounted Transformer (PMT)

Auto Recloser (R)

Pole Box

Flashing Fault Indicator (FFI)

Conductors & Earth wire

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Air Break Switch - Designed to operate on load condition, AB Switches are

numbered in s- series. Oparating hand lever is provided on the botton of pole

with ON/OFF locking facility and can be lock off as a point of isolation.

For safety, open ABS and apply S/L and C/N & simillarly close ABS & L/OFF

Handle upward dirction - ON

Handle downward direction- OFF

- A visual check is reccomended after each operation whether the

contacts are properly inserted/seperated.

- Arcing Shields are provided to minimise the arcing of blades.

- If ABS is deffective , jumper connections are used to bypass it.

Test OH/L, If Dead, Apply Portable Earth

An HV OH/L Tester used to test the isolated line to make sure that the line is

electrically Dead and is always applicable before applying Portable Earth to

commence a work. After isolating & earthing( if facility is available) both ends,

then test the OH/L , If found dead apply Portable Earth at the point of work by

a copetent person with the precense of a senior authourised person.

If the OHL is dead - tester making normal low beep

If OHL is live - tester making high beep

( Before and after the tester itself should be check )

Portable Earth(PE):-Before doing any kind of work on OH/L, the Portable

Earth must be applied at point of work and is very essential to give a Permit to

Work(PTW) . So before issuing PTW, the System Control Engineer should

confirm that the PE is applied at the point of work and simillarly he should

confirm that PE is removed after the work for cancellation of a PTW.

At point of work

PE is applied by the competent person on the OH/L by means of an

insulated oparating rod. The PE circuit consits of four wires and one lead of

each wire is connected together. Then first connect one wire to the Earth wire

and then the other three wires to R,Y,B, phases. After the work , the PE must

be removed fom the OH/L. While removing PE, first disconnect R,Y,B phases

wires and finally disconnect the wire from the earth conductor.

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Pole Mounted Transformer (PMT)Pole Mouted transformer (PMT) are transformer,which is mounted on an OH/L

pole PMT ratings are normally 100 KVA, 200 KVA and 500 KVA. Vector group

is Dynll.

Lightning Arresters are provided nearer to the transformer to protect it

from lightning surges.Possitioning is always in between the transformer

and OH/L line. LA provided at PMT, Pole Box and Auto Recloser

Drop Out fuses are provided for the transformer

protection.Replacement of D.O fuses is permitted under live condition..

Out going cable with Fuse Cut – outs are used to feed the LT 3phase 4

wire system. Ratings available are 100 A, 200 A , 315 A .

Earthing arrangement for PMT – Normally two Earth pits are provided,

one for ground /Body Earthing and the other one is for system neutral

earthing.

Pole BoxTermination in a pole which provides connection between OH/L

circuit and UG Cable circuit is called a Pole Box. The HT cable may be either

from any I/D Substation / Out Door Substation or from another OH/L portion

due to crossing of road / EHT line.

CT and Earth Fault Indicators are provided in some Pole Box to

indicate earth fault passage

LA's are provided to protect the cable termination from lightning surges.

Separate Earthing is needed for pole Box.

Auto reclosersAuto recloser is provided to restore the service continuity after a

transient fault on OH/L. Faults which are not permanent called transient fault.

90% of the faults in OH/L are of transient nature, after a short time called the

dead time, the CB can be reclosed.

Auto recloser will trip the circuit for a fault beyond it (O/C or E/F) and it

save the healthy section.

Auto Recloser normally provided nearer to the AB Switch and that will

helps to isolate the faulty portion and there by restore the healthy

portion after opening the AB switch

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CT's are also inserted with the Auto Recloser, to measure the load

current for protection.

Different type used in Kahramaa OHL System

In Kahramaa distribution system, Auto Reclosers used as sectionalizers since

the Auto reclosing feature is disabled. Auto Recloser should not consider as a

point of isolation. According to the operation and control, two types of

Recloser are used in OH/L System.

Auto reclosers with manual control

During fault, the auto recloser trips the circuit. But after the first opening, the

recloser attains Lock-Off. Manual operation is needed for closing the Auto

recloser and this is done by using an insulated operating rod. First the

operator should manually reset the switch and then close.

Auto reclosers with auto control

A microprocessor control is provided along with the Auto recloser and is

mounted on the pole (bottom). The operator can operate it from the ground

itself. This type of Auto recloser trips the OH/L faulty section and attains to

lock off. Closing after patrolling and clearing the fault is possible from the

automatic control installation. This type of auto recloser should protect the

OH/L section from O/C, short circuit, E/F and sensitive E/F.

Main Components

Battery – 240/ 120 V AC is required to charge the battery.

VT - VT's are the voltage source for charging the battery

It always provided in the source side of the Auto recloser.

LA - Lighting Arresters are provided to protect A/R.

Flashing Fault indicator

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It is a device that is used to identify the earth fault passage. FFI

flashes only when the fault current passing through it. Its location is always

nearer to the AB switch and is clip on to the OH/L.

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National Control Centre

Qatar Power System Over viewPower Station – Installed Capacity

RAS ABU FONTAS A - 497 MW

RAS ABU FONTAS – B/B1 - 996 MW

RAS LAFFAN - 756 MW

RAS ABU ABOUD - 107 MW

SATALLITE STATIONS

i. AL WAJBAH

ii. SALIYAH

iii. DSS - 473 MW

Q- POWER - 699 MW

TOTAL 3528 MW

Transmission networkKahramaa transmission grid consists of the following voltage levels.

Transmission Network

220 KV

132 KV

66 KV

Distribution Network

11KV

0.433 KV

There are 100 Nos. of transmission substation out of which 90 Nos. are

Primary Substations. They are facilitating to feed 11 KV distribution systems.

The primary substations can be either any of the following type.

1. 220 / 132 / 66 / 11KV

2. 132 / 66 / 11KV

3. 220 / 66 / 11KV

4. 66 / 11KV

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Demand ProfileThe domestic consumption is more predominant in the system and domestic

load contributes major portion of the total demand. Remaining are industrial

and they contribute very less, near about 15% of the load (approx. 450

mw).Seasonal variations are predominant because of the extreme climatic

conditions. In summer, hot season begins from May – September, the

demand reaches its maximum value But in winter season, (Nov- Feb), the

demand reaches its minimum value.

Power System – Control The National Control Centre (NCC) controls the QGEWC'S power

system in an efficient way. The smooth, stable and efficient grid control is

achieved by the automated control system (SCADA / EMS). Two control

desks are available, they are (I) Generation Desk and the other is (ii)

Switching Desk.

(i) Generation Desk.

Controlling the Active and Reactive power flow to maintain the

system voltage & frequency to a predetermined value.

Act according to the surplus & deficit condition.

Act according to the abnormal condition.

Merit Order Dispatch is observed

Automatic Generation Control is in operation.

(ii) Switching Desk.

Coordinating & controlling to all Switching operations.

Give Sanctions ( PTW & SFT ) to all switching operation

Executing load rearrangement programmes during shut down /

abnormal conditions.

Arranging Periodic / Break down maintenance activities for the

network elements.

Frequency ControlFrequency is controlled by maintaining the balance between Active

power and Demand of the system. This is achieved by Automatic Generation

Control(AGC). AGC will ensure stable frequency by automatic adjustments of

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generation in accordance with the system demand. AGC controls the active

power flow depending upon the current frequency.

Target Frequency

The system should run at a target frequency – 50HZ with minimum deviation

(not exceeding 0.2 %) as far as possible to keep agreeable level of power

supply quality. The frequency band is 49.90 to 50.1 HZ .Beyond the set

frequency band, AGC change over to local. Participation factor percentage is

also selected to determine the degree of involvement of each generator unit in

the AGC mode of operation.

Minimum Spinning Reserve

A spinning reserve equal to the capacity of the largest unit in service is

to be maintained as far as possible.

Operation with less than above or zero spinning reserve is allowed

when there is a short fall of generation capacity during summer peak,

or due to agreed plant maintenance programme, or units purposefully

kept off to avoid plants running winter nights or when generation unit

are agreed to be kept stand by ,to save running hours for anticipated

usage in next summer peak.

Voltage Control (I) Generator MVAR Control

System Voltage is maintained by controlling the reactive power flow.

Due to the highly inductive nature of load, a larger capacity of MVAR is

required. The main MVAR generation source is the generator and all

generators are normally supplying about 50% of the active power as MVAR.

Then the major source and control point of MVAR is generator source.

Voltage is maintained by controlling the MVAR output of generators. The VAR

control can be achieved either through SCADA control or by local control.

(2) Capacitor Bank

Capacitor Banks are provided at remote areas (MVAR Generation) to

control voltage in 11 KV network. Automatic switching facility is available.

When the transformer (Incomer) MVAR is crossed a pre set value,

automatically the capacitor bank will switch on to the system one by one. That

means supplying VAR to the system.

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During summer – Low voltage problem.

During winter : High voltage problem due to capacitive charging of

cables. Reactor compensates the purpose.

Capacitor Bank at

AL GIFARA - 1.5 MVAR x 3 = 4.5 MVAR

AL SULAIMI - 1.5 MVAR x 3 = 4.5 MVAR

(3) Voltage Regulators

Provided in the 11 KV systems across the 11 KV Bus Coupler to regulate the

voltage as required.

(4) Transformer taps changing.

Immediate improvement in voltage to a limited extent is possible by changing

the tap of transformers in the system.

The Remote tap changing cubicle (RTCC) is having different ways of control.

They are:-

(i) Automatic control (with AVR)

(ii) Supervisory control (NCC)

(iii) Manual control (local)

For Grid Transformer - control is done from the NCC (supervisory mode only)

- ON Load Tap changing is possible.

For Primary Transformer (66 / 11KV) – Automatic control mode operation is

enabled with AVR(ON Load Tap Changing)

For Distribution Transformer – OFF load, manual control only permitted.

Operation at Abnormal ConditionsThere are generally two conditions where the system runs on bellow target

frequently.

Condition 1 - When all the plants on bar (POB) are fully loaded and the

frequency starts to drop as the load increases further. This is an anticipated

frequency drop situation.

Action required: - Manual load shedding is required to maintain the system

frequency by NCC.

Action sequence:-

21

1) Request private generation assistance ( QAPCO ,QVC and

QAFCO )

2) If frequency drops to 49.9, instruct QASCO to shed one of

there three arc furnaces.

3) Further drop to 49.9, restrict QASCO to single furnace

operation.

4) If frequency drops again and if the tendency of load is to

increase further, manual domestic load shedding is done.

For manual load shedding, 38 list are now functional, each list given a load

relief of about 40 MW. The manual domestic load shedding list in waiting (out

of the existing prepared list) is shed when the frequently drop to 49.8 HZ. And

if necessary this is continued with next list and so on. Next load shedding list

for cyclic shedding is # 23.

Note: DCC should be informed before domestic shedding, and they inform the

stand by offices concerned. Maximum load shedding time is limited to 2 hrs.

First domestic load and then furnaces are restored and later import of energy

is stopped as frequency improves.

Condition 2 - A Sudden drop in frequency due to an unexpected major

generation loss. This is an unanticipated frequency drop situation.

Action required – In this case automatic under frequency load shedding takes

place at various stages.

1. Automatic under frequency Bulk load shedding.

2. 11KV feeders at Primary s/s (domestic load) are kept selected at

predetermined frequency levels as below for automatic shedding.

Stage 1 A - Setting 49.2 HZ

Stage 1 - Setting 48.8 HZ

Stage 2 - Setting 48.4 HZ

Stage 3 - Setting 48.0 HZ

Stage 4 - Setting 47.8 HZ

Load shedding selector switch at the Primary's can be put in the desired stage

of under frequency tripping.

3. To improve MVAR levels during the under frequency tripping, reactors

are selected to be automatically closed during stage 2, 3, and 4.

22

4. First domestic and later the furnaces to be restored manually when

frequency improves.

Load Re arrangement

In order to meet the outage of network elements like Transformer, EHT line,

Bus section etc, the NCC may instruct the DCC to transformer load from one

Transformer to other or one primary to another primary.

Automatic Voltage Regulator

The voltage Band is 10.8 KV to11.20 KV, with a 100 second delay provides to

allow grid level restoration measures.

23

Distribution Control Centre (DCC)

ObjectiveMonitors and ensures continuous electricity supply for the distribution

network, within the prescribed values of limit violations, giving priority to

security and safety.

Major functions Controls Active & Reactive power flow in the network and there by

regulate the voltage.

Confirms to all the operation are done in strict compliance with the

department safety rules and regulations and there by ensuring system

safety and security.

Control , coordinate and direct to all switching operations by giving

instruction to field engineers for switching in the 11 KV network for

maintenance / repair of network components and for after fault

restoration.

Co-ordinate with NCC, in case of generation shortage or other system

contingency to shed the load in accordance to the prearranged

methods.

Issue permit to work (PTW), sanction for test (SFT) and isolation

certificate for work in distribution network and also ensure for proper

isolation and earthing by giving priority to safety and security.

Immediate restoration of supply after disturbance and there by limiting

interruption to the minimum.

Inform management about any abnormality & important events.

Co-ordinate with other department for the smooth and efficient

functioning of distribution Network.

Network control by using telemetryA telemetry system is provided for the smooth operation and monitoring of

distribution network on real time basis.

24

The circuit breakers of the out going feeders of Primary s/s can be controlled

from the DCC console. This is achieved by RTU and telemetry provided at

PRY & DCC. All data's like, Bus voltage, current (out going feeders) and

Breaker status are transferred to DCC for monitoring and controlling. It also

provided alarm and limits violation condition to remind the Control Engineer to

act accordingly. The available data's in the DCC computer console can be

utilized to originate different report for the smooth functioning of DCC.

Available Data's & facilities

Loading Values of different Primary transformers.

Loading values of different outgoing feeders of PRY

Bus voltages of PRY

Breaker and VT status of PRY

Limit violation, alarm and important events.

All the data's available in the DCC console can be utilized for past and

present system analysis and also helpful for the contingency analysis. The

data's available in the database also helps to originate various technical report

& statistics.

Role of System Control Engineer

1) Switching Programmes- Verification & ExecutionThe switching programme is very essential to perform a

switching operation in the network in order to avoid danger and risk. For all

scheduled works the switching programmes should be sent in prescribed from

in advance (Before 48 hrs, if possible) exceptions can be allowed during

emergency and contingency operation like after fault restoration, emergency

load shifting & back feeding etc. For load balancing among primary's and

among feeders, the DCC should prepare switching programmes and send it to

the O&M section for execution. After receiving a switching programme,

Control Engineer on duty should study the programme in accordance with the

following criteria.

25

Effects of the operation on system- check whether the shut down is

affecting any consumers, and confirm that the field engineer issued

the S/D notice.

Check whether all the safety aspects are taken care of before

execution.

Study the load rearrangement during the shut down, possible way of

back feeding, loading values of feeders and Transformers involved.

Check the load of feeders involved in paralleling at the time of

isolation and live phasing.

Analyze the paralleling involved in the programme and check

whether it is a bad paralleling or not.

Scrutinize the point of isolation, back feeding arrangement in terms

of system security and safety.

Study the loading condition due to the shut down and check whether

the shut down causes any overloading to any feeders and primary

transformers involved in the programme.

Check the substation planning Number and Name, Sequence of

operation and safety aspects related to the programme, date of

execution and duration of shut down etc.

Study the Live phasing route ,loading during Live phasing and

consumer effected (If any VIP Consumer is in the route of 11KV Live

phasing, then alternative path should he selected for doing the

same.

2. Activities on the day of executionThe verified switching programmes can be execute after considering the

following

Present loading of the feeders and transformers of the system

Present loading of feeders and transformers involved during isolation

(shifting load from one feeder to another) and during 11 KV Live

phasing.

Mostly the loading data's of Transformers and feeders are available in DCC

console except some PRY's. S.S.A can be utilized to collect the data's from

the PRY's where telemetry is not available.

26

Special care at the time of paralleling Paralleling should be essential for NOP shifting and 11 KV Live phasing, while

paralleling, the following points to be noted.

Check the load of feeders involved before paralleling.

Check whether it is a bad paralleling.

Check the bus voltage of the Primaries involved.

If possible, request NCC to minimize the voltage difference

between Primaries involved.

Block the tap changing in order to avoid furthers changes in

voltage and thus the unwanted circulating current. This will

minimize bad paralleling effect.

If there is a bad paralleling history then arrange two field engineers

for make & break operation (if possible) or break and make

depending upon the consumer affected.

Check the load on feeder involved after paralleling in order to

confirm the paralleling is successful and is not interrupted the

consumer.

Supply confirmation from the field engineer is very essential after

paralleling.

Before energizing a transformer, study the present loading of feeder

involved and if it will over load after energisation, then study other

possible alternatives.

After the work, DCC can advise the field engineer to establish new

NOP in view of load balance among feeders and Primaries.

3. Fault RestorationInformation about the fault is either any one of the following way

1. NCC will transmit the message if the standby Earth fault alarm initiated

at NCC or if the Primary Transformer CB tripped.

2. Alarm initiated at DCC telemetry console.

3. Information's from the call centre / stand by offices.

Action required:-

27

If the CB of feeder at PRY has not tripped, then retrieve the past data

from data base and compare with the present load and calculate the

load loss. This load loss data will help to find out in which indoor the

tripping has occurred.

For collecting additional information about the tripping, the Control

Engineer can utilize the help of SSA and Stand by Technicians.

Convey all information collected to the Distribution Stand by Engineer

and also give the Tel. No. of SSA who attending the fault. Control

Engineer should instruct the field engineer to proceed to the Indoor /

Outdoor / PRY where the fault is suspected.

If OH/L is involved, then inform ABU HAMUR OH/L section to arrange

the patrolling.

Report the matter to the top officials with details.

Study the possible back feeding arrangement.

Collect all information from the SSA at site and from the Stand by

Engineer like relay indication, EFI status, station supply (Battery) and

abnormalities etc.

With the above information locate the fault as early as possible.

While test charging, keep the relay time setting to the minimum.

Isolate the faulty section, apply C/N, L/ off and apply CME at point of

isolation.

Back feed the healthy portion as possible.

Inform the fault to the O&M section for repair and rectification.

If supply is effected and to be continue for a long time, then arrange

Movable Generator.

Before test charging, if OH/L involved make sure that all of the OH/L

patrolling gang are away from the live system. This is confirmed by

direct contact with Field Engineer.

Prepare Abnormality report, along with detailed logging in Station Log.

Report the final status to the top officials.

IMPORTANT SAFETY PRECAUTIONS

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While executing the switching programme, before first operation check

the switching programme No, Name of work and Name of Engineer.

Execute the programme in a sequential manner.

Give instructions as per the programme to the Field Engineer and ask

him to repeat the given instructions.

Always tell the name and planning No. of location and circuit to the

Engineer.

Note down the time of instruction and time of confirmation of operation.

Before issuing PTW and SFT confirm that the working section is

isolated, Earthed at both ends. And also confirm that the S/L and C/N

applied at the point of isolation.

Always confirm switching positions after cancellation of SFT.

Confirming switching positions after SFT is mandatory because of the

Field Engineer has the approval for the operations of earth switches

under SFT. He has the temporary control over Earth switches during

SFT for the purpose like HV injection, signal injection, colour phasing

etc.

If OH/L involved in the isolated section, apply CME at point of isolation

(if possible) and test OH/L line, if found dead apply Portable Earth at

the point of work. After confirming the above, issue PTW. Before

cancellation of PTW confirm that all CME and portable earth are

removed from the line.

Rack out VT from the line only after isolating both ends. And VT should

be rack in before energizing the cable. VT status should always confirm

before energizing the circuit.

Before HV pressure test, confirm that the transformers are in CME

condition and VT is in rack out condition.

After isolating a circuit breaker (Rack out) always instruct the Field

Engineer to do Trip –Test for the CB.

Before Earthing the transformer, confirm that the MV side is isolated.

Before earthing a section, confirm that the section is dead and isolated.

Apply CME at both ends to a faulty section after isolating both ends.

Also apply S/L and C/N.

29

Always maintain PRY Substation Battery voltage to a value of 110 V

DC.

Always maintain the Indoor Substation Battery voltage to a value of 30

V DC.

Gas pressure should be in green zone for SF6 Outdoor Substation.

When multi permits issued to the same Field Engineer or to different

Field Engineers within the same point of isolation, then the energisation

shall be done only after the cancellation of all holding PTW's within the

isolated section. When multi permits issued to different field engineer,

cross reference numbering is recommended (# CR).

A field engineer can't hold more than one SFT at a time. SFT is issued

by the field engineer to himself and his direct supervision involvement

is required to perform the test.

Proper informational tags must be placed on single line diagram to

avoid any wrong operation.

The field engineer can't suspend the SFT. He has to cancel SFT before

he leaves the site. Any inconvenience occurred to complete the test,

then he should cancel the SFT and also confirm the switching positions

before the leaving the site.

The field engineer can't hold PTW and SFT together.

OTHER IMPORTANT ACTIVITIES

Load shifting / rearrangement as per NCC advise.Some occasions , NCC instruct DCC to shift some load from one Primary to

other as a part of shut down programmes ( Transmission ) or to avoid over

loading of Transformers / feeders. For this arrangement, DCC Control

Engineer on duty should study the present loading of Primary Transformers

and do the possible arrangements.

Voltage Complaints - Voltage complaints received from the consumer can be

solved by the following measures.

Study the present voltage profile.

If possible, request NCC to raise the voltage at 11 KV Bus of PRY.

30

Instruct the Distribution Field Engineer on Stand by duty to attend

the case and to take present voltage of transformer secondary (MV

Voltage) line to line and L-N and also instruct him to verify the

present tap position.

If further increase of tap position is possible, then Switch-off

Transformer and raise the tap. Confirm the voltage and ensure

system back to normal.

In case of PMT, remove the HT fuse and then adjust the tap

position as required.

NOP Shifting:Paralleling between same or different sources is required

Different Situations:-

Load balancing among same or different Primary transformers.

Load balancing among Feeders.

During shut down works – to back feed the load to avoid interruption.

During fault restoration.

To avoid over loading of Feeders and Transformers.

Important Considerations required

Before paralleling, study the voltage profile of sources and block the

tap if required.

Before and after paralleling study the real time loading values of

Feeders and Transformers involved.

Always confirm the supply status and this is necessary to find out

any load loss due to tripping in between.

If the paralleling is having a bad paralleling history, then arrange

make and break with two Field Engineers.

Preparation of Reports1. Commissioning Report.

Collect the relevant details from the Field Engineer and fill up the data in a

prescribed from. The main information's required are as follows

Circuit Labeling Check.

Protection status

Cable / Transformer size

Cable length

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Battery & Battery Charger Voltage

Earth Fault Indicator positioning

2. Abnormality Report

Any abnormality / tripping happened in the system should be recorded in the

Station Log and also prepare an abnormality report of the incident with details

in a prescribed form.

3. PTW and SFT Cards.

Prepared in prescribed form separate for PTW and SFT and which is serially

numbered with brief details particularly about CME, Name of Engineer,

Section isolated, work, Date and Time etc.

4. Station Log

All events recorded by the Control Assistant in a chronological order during

the shift. This includes all the switching operation instructions given by the

Control Engineer.

5. Control Engineer Log Book

Brief reports about the Operations during the shift.

6. Daily Report – system statistics

7. Weekly Maximum Demand Log

8. Daily peak print out.

Communication facility available

Q-Telephone, KM's Pax phone, Hot line telephone and Fax

Construction & Reinforcement section -Distribution,

Introduction

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All the construction & Reinforcement activities connected with Distribution

Network is executed by the construction section. The work includes

strengthening of the distribution system by adding /upgrading the network

elements with the existing network. Adding network elements like Indoor /

outdoor substation, transformer and associated network for meeting

consumer demand are always done under the construction activity. But

upgrading the network is always comes under the reinforcement section. For

any new proposal, the Planning and Design department should conduct the

detailed study and after that the proposal passes over to the construction

section for final execution. So Construction section has a vital role in the

development of Qatar’s distribution Network.

New project execution The Electricity planning Network department submitted all the

proposals to the construction section (Head) for final execution. The

construction section upon receipt of the scheme of works from the planning

department, allocates the schemes to the engineers of the construction

section after obtaining the proper consent from governmental authorities.

ROA wing should arrange the approval from the governmental agencies (Qtel,

Sewerage, Civil engineering Department, Road Division and Water

Department of Kahramaa).

Role of Construction Engineer Estimates the material requirement and coordinate the same with the

suppliers & ABUHAMUR work shop

Coordinate with consumer for execution of scheme

Allocate the work to different contractors and coordinate with them for

final execution.

Prepare an action plan for the proposed work.

Prepare shut down notices before execution, if any supply interruption

anticipated.

Prepare switching programme for shut down and Commissioning. The

switching programme along with the alteration proposed to the existing

system is required to get proper consent from the system control (DCC)

33

in advance (before 48 hrs). For preparing SW / programme, collect

additional information like NOP, Existing Network details etc from DCC

The single line diagram with all details (substation type ,cable length &

type , transformer capacity & Nos ) of the existing network and the

proposed alterations should be send along with the switching

programme to the DCC for concurrent and comments in advance

(before 48 hrs ). Keep a copy of the same ( switching programme &

drawing ) for reference & execution

Execute the work with the consent of DCC on a particular day as

indicated in the switching programme or a day mutually agreed

between the construction engineer & DCC.

Commissioning On the day of execution, the construction engineer should contact

system control engineer, DCC for executing the work as per the

switching program.

The system control engineer should arrange for possible back feeding

and load transfer in order to avoid interruption during the execution of

work.

The switching programme and other activities involved during the

execution shall comply the Safety Rules and Operation memorandum

of QGEWC high voltage system. The system operation memorandum

D15 is followed in this aspect.

Before Commissioning a New Substation / Transformer

- Check the new label and fix it properly and confirm the same to

control (DCC)

- Protection and fault level of CB. Verify and inform to DCC.

- Check the operation of CB.

- Check the station lighting

- Check the trip circuit healthiness

- Check station Battery and Charger.

- Check the transformer before energizing (oil check, tap setting,

name plate, abnormalities etc.)

- Fix operating lock and label for new s/s

34

After checking all the safety aspects, the Construction Engineer can

commission the new s/s with proper consent from the System Control

Engineer.

- Do HV Pressure Test for the new circuit.

- Check 11 KV live phasing for the new joints and Terminations

before paralleling.

- Check Phase Rotation & MV voltage for the new transformer.

If all the above checks are satisfying, then Commission the new system.

Techniques used for system safety

A number of different techniques and procedures are adopted for satisfying

the system safety during construction and maintenance / repair activities in

distribution network. The newly constructed or repaired network element has

to full fill all the standards, before it connecting to the existing system. In

Kahramaa, the techniques and procedures used before connecting a new

network element to the existing system are as follows.

1. Cable Identification.

2. Spiking

3. Colour phasing ( core phasing )

4. 11 KV Jointing work & Termination work on HT cable )

5. HV pressure test for 11 KV cable and Bus Bar

6. Dead phasing check – 11 KV system

7. Live phasing check - 11 KV system

8. Phase rotation check for MV side.

9. MV voltage check.

10.Trip / test check for CB.

11.Relay inter trip check

12.Transformer, Switchgear panel, Switches and Substation observation.

13.Relay setting & fault level.

Cable IdentificationDuring construction and maintenance, the existing cable has to be cut

for fault rectification and for commissioning new substations in between the

35

existing cable. Then the Field Engineer should confirm the cable which is

going to be cut is the same cable that he isolated and earthed for doing the

work. This is required only where more cables are present with the isolated

and earthed cable. Any mistake will leads to danger to human life and to

system safety. So before doing any work on cable (joints), the field engineer

should always identify the cable by using proper methods.

Safety measures

The cable has to be dead, isolated and earthed at both ends as

per the switching programme and with proper consent from

System Control Engineer.

SFT is required and is issued by the Field Engineer to himself

with consent of system control engineer.

Senior Authorized Person in charge of the work has the full

responsibility of the operation and test

Method

The Identifier kit consists of an Audio Transmitter and Receiver set, by which

the signal generation and reception is possible. For cable identification test,

connect the Audio transmitter between any two phases of the isolated cable

after removing the earth. Keep remote end of cable as earthed for return

path .Then by using the Audio receiver and head phone, we can identify the

cable in which signal is generated. When the receiver is put nearer along the

cable gives a clear beep but varying sound from the cable trough which

transmitted the signal. Sound variation is obtained only from the injected cable

due to the twisting of cable pairs. But for other cables, humming sound is

obtained from live cables and clear beep but not varying is obtained from

dead cable if any. The Cable Identification test is done by the field engineer

himself in charge of work. See the figure.

SpikingAfter identifying the cable, before cutting, spiking has to

require for 100% confirmation that the cable is absolutely dead and safe for

cutting. Spike gun is a special arrangement, where the iron bullet is used for

firing. The spiking gun with bullet is placed over the cable and firing is done

remotely with the help of a rope. If the cable is the correct one, there is no

heavy sound. But for live cables heavy flash over and tripping may occur.

36

Thus spiking will helps to avoid dangerous situation and it provide more safety

to the working personnel's.

Safety measures

The cable should be Dead, isolated and earthed at both ends

with the consent of System Control Engineer.

SFT is required before doing the spiking

After spiking, the cable has to be cut and prepare ends for phasing PTW is

required for any work on cables. But this is a lengthy procedure which can be

reduced subject to pre conditions detailed on Kahramaa S.O.M. No.7.

Colour phasing / Core phasing –Phase identification checkDuring construction / maintenance, cable jointing, break and make termination

works are required. Due to straight jointing perfection and easiness, human

errors and termination difficulties, there may be a chance of colour crossing

while doing cable works with respect to the system colour. So colour phasing

is required during termination & jointing work and is the process of identifying

the 3 phases of system with the 3 core of the cable. Incorrect phasing cannot

be parallel with other systems. So colour phasing is more essential for all type

of jointing / termination works to transfer the same system phase(R, Y, and B)

from one point to other point. Colour crossing of the cable is serious and to

avoid this colour phasing is required during jointing and termination work.

Different methods for colour phasing

1. Banana Resistance and Megger

Connect the three different resistances (known value) to the RYB phases of

one cable end (Star connection with star point earthed) then by using a

Megger, which connected to the other end of cable and measures the

resistance. The corresponding values of resistance obtained on phases will

give the correct phase.

Uni directional LED with Battery set.

Connect the battery between any two phases of cable at the known end. Then

the lamp glow will indicate the phases where the battery connected and it also

37

indicate the direction of current flow. Then from the lamp glow and direction

we can easily confirm the three phases.

Safety

Before doing test, the cable should be isolated, earthed at

both ends with the consent of System Control Engineer.

SFT is required.

General safety measure for Identification, Spike & Colour phasing of cables

Under SFT, the Field Engineer (Senior Authorized Person) has the

approval to operate the earth switch for testing purposes.

The Field Engineer should confirm the switching position after the

cancellation of SFT to the System Control Engineer.

The Field Engineer will be responsible for all such operation or test on

the isolated cable and equipment and also responsible for ensuring

safety , during test.

HT Termination & Jointing works for Cables

All termination & jointing works on cable required PTW. PTW is issued

by the Senior Authorized Person to a competent person (Cable jointer / Fitter)

for doing the work with proper consent from System Control Engineer.

Before issuing PTW for a working section, the System Control Engineer

should confirm that there is no SFT is pending. Issuing PTW and SFT

together for same point of isolation is not permitted. If PTW is issuing after the

SFT, then the Control Engineer should always confirm the switching position

and also confirm that both ends of the cable is isolated and earthed.

Competent person - Kahramaa certified HV Cable jointer / Fitter with

Identity card of Kahramaa

Straight joint kit - XLPE cable to similar XLPE or PILC to similar PILC

Transit joint kit - XLPE cable to PILC or PILC cable to XLPE

Dead joint - Jointing work on Dead cable

Breaking a Termination – Removing an existing cable at a termination point

Making a Termination - Connecting a new cable at a termination point

Break & Make Termination - Breaking and making termination of cable at a

Point during construction / maintenance work

38

Safety

Before doing any work on cables, the cable section must be

isolated & earthed at both ends.

Any work on cables like Break & make terminations, Cable

jointing works required PTW safety document.

PTW is issued by the Senior Authorized Person to the

Competent Person (Cable jointer/Fitter) with the consent of

system control engineer.

The Senior Authorized Person should keep the original copy

of PTW and give a copy of the same to the Competent

Person. After the completion of work, the Competent Person

should give clearance to the Senior Authorized Person for

cancellation of PTW.

High Voltage Pressure Test The High Voltage Pressure Test is compulsory for cables after the

completion of termination and jointing works during construction and

maintenance. The HV Pressure test for new Bus Bar is also required during

construction. The HV Pressure test or injection test is required for cables to

test dielectric strength of insulation. A special HV Pressure Testing Kit is used

for this purpose. During test, -11 KV DC is applied between Phase and

ground(R-E, Y-E, and B-E) and 22 KV DC (-11KV – 0 - +11KV) is applied

between Phases(R-Y, Y-B, and R-B). The duration of HV injection is about 15

minutes for each test. Pressure test is also required to test the perfection of

terminating & jointing work.

Pressure Test Kit

In the testing instrument, meters are provided to indicate the applied KV and

leakage mA of the circuit. If the leakage current value during injection is in

between 0.1 and 1.5 mA, then the cable is declared as healthy. The leakage

current higher than 3mA indicates the breakdown of the circuit. That means

excessive leakage current or tripping indicates that the dielectric strength of

insulation, jointing work / termination work is not up to the standard. If there is

a new bas bar is involved in the circuit, then HV Pressure test for Bus Bar is

also compulsory. For safety, discharge rode is provided with the test kit to

discharge the capacitive charge of cable after the test.

39

Phase to Earth Test

Voltage applied = 11 KV DC (Negative)

(R-E, Y-E and B-E)

Duration - 15 Minutes

Apply – 11KV DC between each phase and earth for 15 minute.

Phase to Phase Test

Voltage applied = 22 KV DC (11 KV 0 +11 KV)

Duration - 15 Minutes

Apply 22 KV DC between R&Y phases for 15 minutes. And repeat the same

test for the other two combinations (R-B & Y-B)

Safety during pressure test

SFT is required for doing Pressure Test.

Before doing Pressure Test, remove all type of earth applied for the

section.

Inform to all the personnel working at site about the test and keep

them away.

The field engineer responsible for the test should confirm that all newly

constructed / repaired elements including Bus Bar, cable joints,

termination are subject to the test.

After the Pressure Test, the SFT taken should return and cancelled

with the consent of system control engineer. Confirm switching

position is mandatory.

11 KV DEAD PHASING

This is a method of checking R, Y, B, phasing of the newly constructed

elements from known end to the other end before live phasing. Dead phasing

will not disturb the existing system. This is a pre - confirmation test before live

phasing.

11 KV LIVE PHASING After all type of constructional / maintenance activities on cables,

terminations, the 11 KV live phasing is required. This is essential for meeting

40

same RYB sequence condition before paralleling between two systems. It

always conducted at I/D substation and it prove that the added network

elements in same phase sequence with respect to the existing. The I/D

Substation nearer to the newly commissioned Substation should be taken in

order to minimize interruption to the consumers.

Live phasing proving the there statements below:-

R phase is connected to Existing System R phase

Y phase is connected to Existing System Y phase

B phase is connected to Existing System B phase

At the time of live phasing, we have two different sources from two stations

and is available at the Bus Bar spout and Cable spout in an Indoor S/S. One

is the existing supply source of I/D substation where the live phasing test to

be carried out and is available at the Bus Bar spout. The other one is the

existing supply taken through the new circuits (includes all terminations, cable

joints, and Bas Bar except the transformer circuit) and is available at the

Cable spout of the Indoor S/S.

Live phasing sticks

Live phasing is proved by measuring the voltage between the phases

available at the Bus Bar spout and the Cable spout. Live phasing sticks

consists of two sticks connected in a special manner with a Voltmeter and one

is inserted in Bus bar spout and the other is inserted in the Cable spout during

the test. The Voltmeter measures the potential difference between the Bus

Bar spout phases and the Cable spout phases. While observing the live

phasing between the two system available at Bus bar spout &

Cable spout, for correct live phasing the voltage should be as follows:-

R of (Bus bar spout) to R (Cable Spout) – 11 KV

Y of (Bus bar spout) to Y (Cable Spout) – 11 KV

B of (Bus bar spout) to B (Cable Spout) – 11 KV

R of (Bus bar spout) to Y (Cable Spout) – 5.5 KV

Y of (Bus bar spout) to B (Cable Spout) – 5.5KV

B of (Bus bar spout) to R (Cable Spout) – 5.5KV

If any mistakes happened during work, then the voltmeter will indicate

incorrect reading. Then the Field Engineer should rectify the mistake.

41

At Indoor substation, the CB towards the new circuit should be kept opened.

Then Bus Bar spout is having the existing supply and cable spout is having

the existing system through the new circuit. By inserting live phasing sticks

between bas bar spout & cable spouts, we can confirm whether the live

phasing is correct or not.

Safety during live phasing

Keep Circuit Breakers of L/TX's at new substation as opened, isolated

and earthed condition ( MV link should be opened before closing Earth

switch)

Include all the terminations, cable joints for checking the live phasing.

Some times including all joints and termination together is not possible

at that time check separately for different routs.

Make sure that all the newly constructed /repaired circuit is included in

the test and have the same phasing with respect to the existing system

phasing.

After successful live phasing check, the Field Engineer should

coordinate with the System Control Engineer for closing the CB

between existing system and new system. Bad paralleling and loading

capacity of feeder should be considered for safety and stability.

Check live phasing at an I/D substation which is mutually agreed

between the Field Engineer and System Control Engineer.

Considerations are minimum interruption, distance traveling, loading,

bad paralleling etc. We can conduct live phasing at any I/D substations

( existing or new one )

If the supply is taken through the new circuit includes an existing O/D

substation, then the existing and new phase rotation has to be check

for consumer safety.

Phase Rotation & MV voltage check for MV side11 KV live phasing only proving that the new HT network elements are

in correct phase with respect to the existing system. But for transformers MV

phase rotation & voltage check is required to ensure that the consumer supply

is not affected due to the alterations and modifications done during the work.

This is required to ensure proper MV voltage and phase rotation to the

consumer.

42

Methods

1. Phase Rotation meter

2. LED Flickering meter

Phase rotation can be checked either by using a phase sequence check

meter (rotating dial with arrow indication) or by using an LED flickering

meter. The rotation in arrow direction indicates the correct Phase

sequence.

Phase rotation check is done at the MV link of transformer.

MV Voltage

Check the voltage at MV panel between three phases and also check the

voltage between phases and neutral.

Correct Value R-N

Y-N - 240 V

B-N

R-Y

B-Y - 433 V

R-B

Safety

Keep the MV side link / ACB as open during the phase rotation and MV

voltage check.

LT side fuse replaced only after the successful commissioning of

transformer.

Close, Trip-Test and recloseTrip-Test

If any CB is Rack out for any operational purpose, then it must be checked

for trip test. This is for a confirmation that all the auxiliary contacts are healthy

as before. Trip test is done by rotating the disc manually and it ensure the

following

Circuit Breaker auxiliary contacts are healthy and okay as before.

Trip circuit is healthy.

Close

If the live phasing is correct, for proving the same the Field Engineer

should close the CB between two systems.

43

Reclose

After proving the live phasing, the system NOP should be as per the

direction of System Control Engineer. That means the close or reclose is

according to the system condition.

Relay inter trip test

Air Circuit Breakers are provided in some consumer panel with

Restricted Earth fault relay ( REF ). REF protects the MV side winding of

transformer and the MV cable up to the point of CT from Earth Fault. Inter trip

feature is provided to trip the HT side CB of transformer during MV fault/ACB

tripping condition. So this inter tripping feature has to be tested before

commissioning the transformer

Physical checks before Commissioning The Field Engineer should observe all the Transformer, Circuit Breakers,

panels, Switch gear room and Switches etc before commissioning the station.

Check the following.

Transformer - Oil check

- Tap position (nominal ‘3’).

- Termination (MV & HV)

- Name plate details (Rating and % Z)

Circuit Breaker - fault level

- Operation check.

- Trip circuit healthiness.

Panel - Circuit labeling.

- Meters to be check for its functioning.

- provide operational locks.

- relay setting & trip circuit status.

Substation and Switchgear room - Planning Number.

- Door Lock.

- DC Battery Voltage check.

- Battery charger healthiness.

- Station lighting.

Operation & Maintance section, Distribution, Kahramaa

44

Introduction

The smooth functioning of distribution system is always in

accordance with the performance of its operation & maintenance team. So

continuous and reliable supply is ensured only through the better and efficient

performane of the operational and maintanance section of the department. In

Kahramaa, this is achieved through the engineering wing and workforce.

Engineering wing is headed by one senior engineer and execution of

oparational & maintenance activities are done by the group of Field

Engineers. Work force is available at the ABU HAMUR work shop and from

there the work is arranged and cordinated. The material and manpower for a

work should be arranged from the ABU HAMUR workshop. LT maintance and

operational activities are done by the different distribution stand by offices.

Cordination of stand by offices are done by the DOHA call centre. The Field

Engineers can use the help of stand by offices and that is depend on their

availability.The O &M works includes the repairs of Switchgear and the

network elements.The ultimate aim of all activity is to deliver good quality

power supply to the consumers without interruption.

O & M Section activitiesAll switching operation for the operational & maint works is done by the

field engineers. Operational and maintenance activities can be subdivided into

the following categories.

i. Preventive Maintenance : - Preventing a future breakdown and

ensure continuous supply. All periodic scheduled maintenance

on the 11 KV Distribution system is comes under this category.

Regular systematic maintenance, all preventive action taken for

the smooth & efficient operation of the system. Servicing,

Overhauling and routine oil and gas check are examples.

ii. Corrective maintenance or Breakdown Maintenance :- This is the

corrective actions taken for the smooth and efficient operation of

the system. The Break down or corrective maintenance

activities are conducted after the failure of an equipment. Such

maintenance results in outage of circuit and supply. In general,

it consists of locating the trouble, repair and recommissioning.

45

General duties of O&M Field engineersAll switching operations for O&M work are done by field engineers on duty

1) Periodic repair & maintenance – Preventive works-oil /gas

changing, servicing etc.

2) Break down Maintenance -TX replacement, Faulty Cable

rectification etc.

3) Emergency break down duty - stand by engineer generally attend

this duty on rotation basis. Loss of supply due to tripping and

emergency load shifting are coming under this category.

4) System operation duty - The spare field engineer should attend

the load rearrangement works as per switching programme (NOP

shifting) for the smooth running of system as per the request of

system operation (DCC).

5) Cable fault: - The field engineer (Cable fault) on duty should

locate the cable fault. After finding the fault, the field engineer has to

arrange the excavation team and the cable jointer. After repairing he

has to restore the supply.

All these above discussed activities should be coordinated by the

senior Engineer of O&M and shall comply the safety practice and Operation

Memorandum of Kahramaa. The interference to the live system is permitted

only with the proper consent from the System Control Engineer on duty

(DCC). So for all the work (operational, repair and maintenance ) the field

engineer should obtain proper consent from System Control Engineer (DCC).

Immediate supply Restoration:- Immediate supply restoration always gives better service to

consumers and is important in distribution system. The kahramaa distribution

system has adopted an efficient and effective way for overcoming the

emergency breakdown condition. The field engineer are posted on a round

the clock rotation basis for the stand by duty in order to attend the emergency

tripping conditions and restoration thereon. During the tripping and emergency

condition, the system control engineer should co-ordinate and directs the field

engineers for immediate restoration. The system control engineer should

46

direct and co-ordinate by giving instructions to the field engineer as per the

relay indication and other field information. First, he should find out the faulty

portion and then isolate it from the healthy system and then restore the

remaining healthy system as early as possible. After that, DCC Control

engineer has to direct and coordinate the field engineer to rectify the faulty

section as early as possible. All the above switching operation must be done

according to the safety rules & as per the Operation Memorandum of

kahramaa.

The stand by offices staff provides assistance to locate the fault during the

restoration process. Along with the stand by office staff, kahramaa has

substation attendants who comes under NCC and posted to some Primary

Substations. The SSA also provides necessary assistance during a fault or

system disturbance. Apart from the above, kahramaa providing stand by

diesel generators, this is capable of delivering power to the interrupted

consumers. DG Set allocation is mainly depends on the duration of

interruption and the nature of consumer.

Load re- arrangement (NOP Shifting)As discussed in the introduction, in kahramaa distribution system, the open

ended Ring main system (Ring –off with NOP) is mostly used. NOP is the

normally opened points in the 11 KV Distribution systems and is shifted to

transfer load from one primary to another or shifted load from one feeder to

another feeder of same primary. NOP is provided for the smooth operation of

system grid and for operational flexibility. Closed Ring operation is also

provided for some important distribution consumers. But mostly all I/D and

O/D substations are feeding from one source at a time and there is always

one or more alternative sources (either from same or different PRY) are

available as NOP. Some Radial feeding s/s and multiple source feeding s/s

are also available (same primary). The location of NOP decides the loading of

the 11 KV feeders which in turn reflects the loading of the transformers of the

Primary Substation.

NOP shifting will always helps to balance the loading among 11 KV feeder/

primary transformers and also helps to back feed the system at the time of

supply failure. There NOP shifting can be execute either by a pre-planned

manner (prior switching programmers) or for an emergency situation like over

47

loading / tripping of feeder / transformer (PRY). If it is in urgent nature, then

the field engineer on stand by duty has to attend the NOP shifting. The pre-

planned NOP shifting programme is normally executed by the field engineer

on system operation duty.

For system operation load shifting (NOP- Shifting), the DCC

should prepare the switching programme and the switching is

done by the field engineer.

Work fore for Distribution Kahramaa is having a strong work fore to do its operational,

maintenance, repair and construction activities of the distribution system.

Abu Hamur workshopAll repair / maintenance activities for switch gears, panels,

transformers, switches etc are done at this work shop. There are different

section are working under the Head of workshop. The man power for the O&M

activities and constructional activities are also supplied from this work

shop .Round the clock duty is also available for some important areas.

Fitting Section

OHL Section

Cable section

Diesel Generator section

Stand by OfficesStand by offices are under the system operation department (DCC).Their

primary duty is providing service to the consumers (MV / side service). Supply

interruption of the consumer is attended by the stand by office Staff.

Depending on their availability, the O&M, Construction and DCC can

utilize them for finding Substation location and for collecting information’s from

site etc.

1. DOHA STAND BY / EMERGENCY CALL CENTRE2. KHALIFA TOWN STAND BY

3. RAYYAN STAND BY

4. WAKRAH STAND BY

48

5. M. SALAL STAND BY

6. KHORE STAND BY

7. AL- GHOWAIRIYA STAND BY

8. SHAHANIYA STAND BY

9. RUWAIS STAND BY

Substation Assistant –SSAControlling from NCC / DCC

Duty - Primary substation

-Collecting information’s from the different sites as per the requirement

of NCC/DCC.

Switching ProgrammeA group of sequential operation and activities required to avail shutdown for a

live system to perform some operational, repair / Maintenance work and to

energize back the system to normal after completion of work.

Switching Programme Form

Operation No Location Circuit Operation Time Initial

Work Execution

For arranged work like preventive maintenance,Corrective

maintenance, the field engineer should prepare the switching

programme after obtaining proper data from DCC and send to the DCC

prior to the execution(48 hrs before).

For emergency break down / tripping work the field engineer should

operate according to the proper instruction from control engineer on

duty ( DCC).

Distribution System Protection

Introduction

49

The function of a protection scheme is to ensure the maximum continuity of

supply. This is done by detecting the faults and isolating the minimum

possible part of power system during fault and abnormal condition. Protective

relays are the devices that detect abnormal conditions in the Electrical power

system by constantly monitoring and measuring Electrical quantities as well

as various other parameters to discriminate between Normal and abnormal

conditions. The basic Electrical quantities which are monitored for detecting

abnormal conditions are

Voltage

Current

Phase Angle

Frequency

Discrimination

Discrimination is the ability of the protective relaying scheme to determine the

point at which the fault occurs and isolate (by mean of Tripping actions) only

the faulty element or section. Basically there are there methods of

Discrimination.

Time Discrimination

Comparison Discrimination

Magnitude Discrimination

When more than one protective device is used in series, it is necessary to

have discrimination between these protective devices.

Types of faults The most common fault that can occur on a power system are as follows

1) There phase fault (L-L-L)

2) There phase to ground (L-L-L-G)

3) Phase to phase (L-L)

4) Phase to ground (L-G)

5) Phase to Phase with ground (L-L-G)

Faults in system

Cable faults – Joint faults, termination faults and third party damage

Transformer faults – Incipient faults, over loads, terminal faults, winding

faults and through faults

50

Switch gear faults – Flash over due to insulation failure

Bus bar faults

Natural events

Physical accidents

Mal operation

Kahramaa Distribution system protectionThe protection scheme used in Distribution Network including the Primary

substation, Indoor substation and outdoor substation are detailed below.

Primary Substation protectionThe protection schemes at a typical primary substation 66/11KV with 2 X 40

MVA Transformers is as follows.

1. Transformer Differential – Instantaneous relay

Unit Protection scheme protects the LV & HV windings of the Transformer

from internal faults (short circuit & heavy Earth fault) protected zone is in

between the LV & HV side CT’s

2. HV side REF Protection – Instantaneous relay –4B3 type

A type of Unit protection and it protects the HV side winding of transformer.

REF is highly sensitive to all Earth faults. Protected zone is within the line

CT’s and neutral CT’s. A small Protection of winding nearer to the neutral

remains as unprotected.

3. LV REF Protection – Instantaneous relay

It Protects the LV side winding of transformer from internal Earth faults.

4. HV side IDMT Relay - (2 O/C+1 E/F)-Type –TJ M10.

A type of Back up protection and it protects the transformer from HV Side

Over currents and Earth faults.

5. LV Side – Directional Over current and E/F Protection (DOC)

It always directed towards transformer LV winding. Protects the transformer

from heavy circulating current occurred at the time of tap changing and it also

protect the other source in the same Bus from the internal LV fault of the

transformer.

51

6) Temperature, Gas and oil surge protection for transformer

Main TX Bucholz /PRV trip

Tap changer Bucholz surge/gas trip

Earthing TX Bucholz surge trip

Main Transformer winding temp trip

Eathing TZ Bucholz Alarm

Earthing TX low oil level

Main TX Bucholz Alarm

Main TX winding temp alarm

Main TX low oil level

Other Relays

Master trip Relay-All relays are wired to the master trip to initiate the tripping

signal for Circuit breaker. Type –F8H trip relay.

Pilot wire inter trip –Type TEC Relay

Pilot wire protection sustained inter trip -Type TC-5

Earthing transformer and system protections Since the Primary transformer is star delta, an Earthing transformers OF 500

KVA with Zig Zag winding is used on the 11 KV side with tertiary delta

winding.

Tertiary – 166.6KVA

11/0.415KV

Percentage impedance – 4.23 %

Impedance per phase is 27.5 ohm

Maximum fault current for 3 seconds is 750 A

Earthing transformer is required for the following purposes

The earthing transformer is mainly used for the earthing purpose. It

creates an artificial neutral point on the delta 11 KV side winding.

Used to limit the fault current to a maximum of 750 Amps

52

Used for the purpose of SBEF protection and also for the REF

protection

Used to provide Auxiliary supply to primary substations (415 volts)

Stand by Earth fault ProtectionStand by earth fault relay is provided in the secondary circuit of earthing

transformer neutral CT. If an earth fault is not cleared by appropriate Circuit

breaker of 11KV feeder in the Primary substation, the earth fault current will

continue to flow through of the 66/11KV transformers in the Primary

substation.

If the fault persists without clearing by the feeder earth fault protection the

fault will be cleared by the SBEF stage 1 and 2 timer relays. Stage 1 will trip

the bus section and stage 2 will trip the transformer. Main features are as

follows.

o Protects the 11 KV distribution systems including the Primary

transformer LV winding from Earth fault and the maximum earth fault

clearing time is limited 3 seconds.

o The SBEF relay will initiate “Flag ON” condition for all earth faults

(magnitude higher than the set value). Current setting depends on the

independence of the Earthing transformer.

o If the fault is not cleared by the appropriate feeder earth fault

protection, then it will be cleared by the SBEF stage 1 & stage 2 timer

relays. SBEF stage 1 will trip the bus section CB after a definite time

delay of 2.4 seconds and stage 2 will trips the CB,s of faulty section

transformer HV and LV side after 3 seconds definite time delay.

o Relay operation will initiates alarm in NCC and PRY

In Kahramaa Earthing transformers are designed to allow a maximum fault

current of approximately 750 Amps for 3 seconds and Normal current setting

is 20%. C/T Ratio for SBEF protection is 750/1

(27.5/ phase – impedance of ETX)

Effective impedance (27.5/3) =9.16 OHM

I fault (Max) = 11000 / 3x9.16 =694 =750A for 3 Sec

53

SBEF - Flag ON initiated at NCC and PRY sub station

(If the If is set value)

Stage-1 –Trips the Bus coupler CB after 2.4sec

Stage-2 – Trips both the HV & LV side CB of PRY TX after 3 sec

11 KV Bus bar Protection 1. Partial Bus bar Protection

2. SBEF where there is no partial bus bar protection and in the substations

with partial bus bar, SBEF act as a back up protection.

Partial Bus bar protection Partial bus bar deferential protection employed in the 11 KV feeders of

primary substation equipped with bus section breaker. This relay works on

deferential principle and the relay is connected across the secondary CT's of

bus coupler and incomer with an overlapping arrangement. The feeder CT’s

are not involved in this scheme of protection causes relay operation during

through fault condition. To avoid this, discrimination between Bus Bar fault

and 11 KV feeder faults is provided. Main features are as follows.

It protects a portion of Bus Bar from bus Bar faults and provides a back up

protection for the 11 KV feeders. For 11 KV system faults feeder protection

act first and when it fails partial bus bar protection will act as back up.

The phase fault element of the partial Bus Bar protection is graded with

the feeder phase fault protection and Earth fault element is graded with

feeder Earth fault element and stand by Earth fault protection.

In Partial Bus Bar, its 50 element (Hi set) 100m sec delayed operation is

enabled to avoid the tripping in through fault condition. After 100 m second

delay, the partial Bus Bar relay will trips the Three CB's (Bus coupler CB,

HV& LV CB of faulty section transformer).

51 element of partial Bus Bar act as a back up protection to outgoing

feeders. A time grading of 300 millisecond is provided between the IDMT

O/C elements of Out going feeders & PB relay and Transformer HV O/C

For Internal Fault

54

PBDP- 50 element (High set) - will operate after 100 milli sec delay.

For External Fault (Through fault)

PBDP –50 high elements will receive a blocking signal from the out going

feeder 1DMT (50 element hi set) within the 100 milli sec time, Then its

operation is blocked by the feeder IDMT (Hi set). If the feeder fails to

send blocking signal, PBDP (50 high set)will trips the LV ,HV side breakers of

transformer along with the Bus coupler breaker.51 elements act as a back up

protection for the feeder

Grading

50element -100 milli sec time delayed operation.

51element (O/C) – graded with the feeder IDMT O/C and TX HV side O/C

(Time grading only possible - 300 milli sec)

51 element (E/F) - graded with feeder E/F (IDMT) and SBEF

(Magnitude grading only possible)

CT is -2000/1; current setting is normally 7% (300 m sec time grading)

Primary substation feeder protectionNormal protection scheme consist of the following relays.

1. Pilot wire protection

2. Standard IDMT Relays (2 O/C +1E/F)

Pilot wire protection A type of unit protection

Solkor R instantaneous protection (60 milli sec)

Relay operates on either current or voltage comparison

Used as main protection in feeders

Pilot wires interconnect the CTs at each end of the line. Employing the well-

known differential principle this would compare the current entering the line

with the current leaving the line. In practice two relays are connected at each

end of the line connected by two pilot wires. Summation CT is used for

converting multiple input quantities from a 3 phase system quantity to a single

phase quantity.

55

For Internal fault - fault within the two CT’s

Difference in current (entering & leaving) causes relay operation and trips the

CB at both ends.

For External fault

Entering and Leaving current is same. No current flow through the relay coil

and

relay remains stable.

Important points

The padding Resistance to set to a value such that, the total loop

resistance of the pilot wire cable is 1000 Ω. Let RL be the Pilot wire

lead resistance. There the padding resistor to be provided at each end

is , RP =1000-RL Ω (RL is normally about 10 Ω).

Current Check Relay (B 69 Relay) is used in series with the SOLKOR

Relay and it will prevent the tripping of the 11 KV cable feeder on

account of any pilot wire open condition or pilot wire shorted condition.

For the current check Relay the O/C setting is provided with more than

the O/C setting of the IDMT O/C relay on the feeder.

Pilot wire supervision relay is also used to detect any fault in the pilot

wire circuit and for any type of fault in the pilot wire

If pilot wire supervisor Relay or current check relay is not provided

along with SOLOKOR R Relay, the following situations can occur

SOLOKOR R unit protection acted and the Feeder trips only at receiving end,

it can be assumed that it is pilot wire problem and in this Situation, the feeder

not to be put in service until the Pilot wire unit protection is decommissioned.

The sending end of the feeder Tripped on SOLKOR R unit protection but no

tripping at the receiving end. Then in this situation the feeder not to be put in

service until the 11kv cable is meggered. On meggering, if no fault is found

on the Cable, then the feeder to be charged from the sending end.

Standard IDMT Over current and Earth fault relays Simplest type of protection

56

Protect the feeder and network elements from O/C and E/F

Time and Current grading or combination is possible

Standard IDMT relay is provided (2O/C(R and B phases) +1E/F(Y phase))

Induction type – TJM10 and Static relay-MCGG52

Normal current setting is 125% for O/C element and 40% is for E/F element

with a time setting of 0.4 TSM

Some IDMT relays are provided with stage 1 & stage 2 operation features

Stage 1 –50(High set element) & 51(IDMT element)

Where 50 high set is used for SOTF (Switch on to fault) feature.

100 milli sec –300 milli sec delayed operation is provided for this type relay in

order to avoid tripping during heavy inrush currents (100 m sec –300 m sec) is

the decaying time required for inrush. In some cases, SOTF protection is also

provided with Harmonic Restraint feature (100 millisecond delay ) or with out

Harmonic Restraint feature (300 millisecond delay ). The 2nd Harmonics from

magnetizing inrush currents or switching surges will decay with in 300 milli

second.

51- Normal IDMT element with grading.

Stage-2

50 element - Initiate blocking signal to the Partial Bus bar high set element

and the signal will reach within 60 milli sec. during a fault in the out going

feeder. The High set element of IDMT relay is not used for tripping but it

sending blocking signal to the partial Bus bar relay.

Relay OperationFor Three phase balanced fault – R&B O/C relay will operate.

For Three phase earth fault - R&B O/C relay will operate

Phase to phase fault - R or B phase O/C relay will operate

Phase to phase to earth fault R or B phase O/C+E/F will operate

IDMT act as primary protection in feeders where pilot wire protection not

commissioned. If an Out going feeder is commissioned with pilot wire

protection, then the IDMT relay act as a back up protection.

57

Protection used in Indoor SubstationFeeders-1) Standard IDMT relay (2O/C(R and B phases) +1E/F(Y phase))

Induction type – TJM10 and Static relay-MCGG52

2) Pilot wire protection - SOLKER R instantaneous tripping

Pilot wire protection (SOLOKOR R) is provided in cables between two

indoors and also provided between the Indoor and Primary s/s.

Bleed off feature is available for 20% of the cable full load. That means

for a 300 ampere cable, 20% bleed off is allowed (60A).

Transformer protection – 11/.433KV HV side is protected by EIDMT O/C & E/F protection with separate

High set instantaneous element for O/C and E/F.

LV side winding and cable up to the CT point is protected by Restricted

Earth fault protection. (In case of consumer MV panel with ACB and

REF relay available)

From MV panel REF relay to HV panel, intertrip cable used for the

connection for 11 KV inter tripping.

IDMT relay with EI Characteristic is used. This Provides better grading

with the MV fuses. Type TJM 31 &2TJm31.

Separate High set instantaneous element is provided to protect

transformer from heavy fault

Current setting and CT ratio required is as per the transformer capacity

High set relay setting is as per the short circuit fault current of the

transformer. (To avoid the unwanted tripping due to magnetizing inrush

current, 130% of the expected fault current is taken for relay current

setting)

MV side protection - Fuse protection is available.

- ACB with REF is provided in some consumer panel

Time and Current grading

58

In Radial feeders, Standard IDMT relays are graded with time and current

discrimination.

PRY substations relay setting (O/C element) -125% plug setting with 0.4 TSM

PRY substation relay setting (E/F element) - 40% plug setting with 0.4 TSM

First Indoor S/S setting (O/C element) - 100% plug setting with 0.275 TSM

First Indoor S/S setting (E/F element) - 30% plug setting with 0.275 TSM

From first indoor the current setting is fixed as 100% for O/C and 30% for E/F.

Then the protection is graded by time and always keeps a grading margin of

0.125 TSM to avoid false tripping. The maximum grading stages allowed is 3.

Protection used in Out door Substation Feeder - no protection is available

- EFI is provided to identify the path of earth fault current.

Transformer -Oil Fuse Switch

HRC fuses are used to protect HV side

Transformer rating and Fuse required

500 KVA - 40A

800 KVA - 60A

1000 KVA - 60A

1600 KVA - 90A

Transformer with SF6 TX switch

Time lag fuses are provided in the CT secondary circuit to protect HV side.

TLF required for Transformers with different CT is shown below.

Voltage

KV

TX Rating

KVA

CT Ratio

A

TLF rating

A

Max.distributo

r fuse link

rating

A

59

11 200 50/5 3 160

11 300 50/5 5 250

11 500 50/5 7.5 315

11 800 50/5 12.5 400

11 1000 100/5 7.5 500

11 1250 100/5 10 630

11 1500 100/5 12.5 630

11 1600 100/5 12.5 630

Parallel Feeder ProtectionSource end -IDMT relay (51)

Load end - Directional relay(67)

Closed Ring

Protection schemes required for a closed ring system are as follows

Pilot wire protection (SOLKOR R-type) should be commissioned before

closing a Ring system. Ring splitter should be provided in order to separate

the ring at the time of tripping of Bus coupler CB by the operation of

PBDP/SBEF protection during the fault. Ring splitter is an IDMT relay with

current setting 100% for O/C and 20% for E/F element. The time setting

should be minimum (0.1 TSM)

OR

Combination of IDMT relays (Directional &Non –Directional) with Ring splitter.

Over head line protection IDMT (2 O/C+E/F)

Sensitive Earth fault protection

Sensitive Earth fault protection

IN OH/L, the earth path resistivity is very high and then the normal E/F relay

will not detect the earth fault of the system. To overcome, this condition OH/L

60

are provided with sensitive earth fault relay (current setting is 3% with a long

definite time lag of 3 seconds).

CT Ratio - standardsPrimary substation

LV side of TX and Bus bar - 2000/1 for PBDP

-2000/1 for D O/C and D E/F

Out going Feeders - 400/1 or 300/1 for IDMT, SOLOKER R & Metering

Earthing Transformer - 750/1 (Neutral CT)

Indoor substation

Feeders - 300/5 or 400/5 for SOLKER R, IDMT and

metering.

Transformers - 150/100/50/5, 80/40/5, 60/30/5, 100/50/5

for IDMT & Metering

Out door substation

Transformer with SF6 TX Switch – 100/5 or 50/5

CT classIDMT Relays - 5P10, 15VA

SOLKER R (for differential type) - Class x

Metering - Class 1

Battery supply availablePrimary substation - 110V DC

Indoor Substation - 30V DC

General Informations Operation & safety locks.

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Co2 System features.

Location map

NO P Shifting

Bad paralleling and Tap Blocking

Confirm supply in I/D and O/D Substations.

Substation & Circuit Identification.

System Safety.

Circuit Breakers – Method of isolation.

Pot End & Cap End Cables.

Operational & Safety Locks with Keys.

For better operational and system safety, kahramaa provided Operational and

Safety locks with keys to their Field engineers. Apart from operational & safety

lock, Substation keys are also available and is provided to all field engineers

and to some contractors.

Operational lock with key

Indoor and Outdoor Substations

All Switches, Circuit Breakers, Panels, Isolating and Earthing devices are

provided with Operational lock with key. Normally two types available and

given to all Field Engineers.

1) 246 Type

2) Den ( Department of electricity network )- small size

Strictly follow kahramaa's Safety Rules, while using the operational locks

during the work.

Primary Substation

Separate operational lock sets are provided for each circuit of Primary

Substation. A main key box is fixed in all Primaries. Any circuit is taken for

PTW / SFT, then after proper locking the corresponding key set for the circuit

should be kept under safe custody in separate Danger Envelop as per Safety

Rules. The Operation and handling of PRY keys is limited to the Field

Engineers.

Substation Gate locks with key

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1. Primary Substation gate key

2. I/D & O/D Substation gate key – 2 types

Substation gate keys are giving to all Field Engineers and to some

Contractors.

Safety locks with key

This is separate lock, unique in nature with key and is an additional

Safety measure during Switching. Safety locks preferably differing from

standard locks of the system shall be used to lock off all switches at points

where the circuit on which work is to be carried out could be energized. The

keys for such locks shall be kept in a key safe, if provided, or in some other

safe place preferably in the possession of the Senior Authorized Person in

charge of the work. See Kahramaa Safety Rules12.3

Locking facility available for Indoor VCB Bus Bar spout shutter

Feeder spout shutter

Earth Switches

Push Button ( Trip / Close )

Panel Door

Interlocking features available Without opening the OCB, the inter locking lever will not be

disengaged.

The Isolating lever entry is possible only when the OCB/VCB in opened

condition.

Closing of Earth Switch is allowed only when the VCB is in Racked

Out/Test position.

Closed condition of Earth Switch will not permit to Rack in UCB into

Service position.

When VCB is in Service position, the Earth Switch closure not allowed.

CO2- Automatic spraying system for 11 KV Switchgear room at PRY

All Primary Substation with 11 KV OCB switchgears are equipped with an

automatic CO2 spraying system in its Switchgear room for the safety of

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switchgears. Castle – key interlocking system facility is also provided for

personal safety. During the switching operation / any other purposes the field

engineer (SAP) is required to enter this room, then the automatic spraying

mechanism should be blocked temporarily to prevent accidental operation. So

there is an inter locking facility is provided and is designed that, a person will

get the key of switchgear room only after blocking the automatic spraying

feature of CO2. A separate control system is provided for controlling the

operation from a nearby room. After the operation, the Field Engineer should

normalize the system as before.

A data transfer is provided to transfer the operation status of CO2 spraying

system (Automatic / blocked / manual) to NCC and it will gives alarm for the

changes in operation. So the field engineer should inform NCC before doing

any operation.

Confirm SupplyOut Door Substation

Check the humming sound of Local Transformer.

Check the vibration of transformer.

Ammeter Indication from MV panel / Feeder pillar.

Indoor Substation

Check Transformer humming sound & vibration.

Check Meters indication in the switchgear panel

Check Station Battery charger voltage.

Station lighting.

Location MapAn up to date location route map is provided to all Field Engineers for helping

them to find out the Location of Substation.

Substation Labeling

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Name with voltage level (capital letters) displayed for Primary Substation.

Indoor and Out door Substation:-

Name plate with Planning Number and Name displayed.

If there is no name plate label, then substation can be confirmed by checking

the circuit label.

Circuit IdentificationOnce the substation is identified, then the circuit can be confirmed by the

circuit label and name plate provided on each circuit (Feeders and L/TX)

If circuit label is absent or not legible then the method of confirming the

circuits are:-

1. In Out door substation, Earth Fault Indicator positioning is normally in

left hand side circuit of RMU.

2. Cable size & type as per mimic diagram available at DCC.

3. If all the identification procedures fails, then the Field Engineer can

identify the circuit by switching operation from the remote / adjacent

(Feeding) substation. (First switch off the substation where

identification failed and then close the main switch one by one. Then

identify the circuit from the feeding source by checking the station

supply.)

Pot End & Cap End CablesPot End ( P.E ) - Idly charged cable without connected load.

One ends of the cable is connected to the 11KV Bus and the other end is kept

free ( not terminated but the terminals are made and covered with a pot

termination kit ). Pot End cable is idly charged from one end.

Cap end ( C.E ) - Earthed Cable

One end of the cable is connected to the 11 KV Bus and the other end is kept

free, not terminated but only covered with a cap. The cap End cable is always

in earthed condition from its 11 KV Bus side.

Parallel Operation

Condition for parallel operation of two systems

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1. frequency,

2. Voltage and

3. Phase sequence should be same

In Kahramaa, QGEWC system, the frequency is same. There is no

interconnecting system. The phase sequence can be correct is there any

mistake. Then the only one depending variable is voltage. So, the voltage

variation between the two sources for paralleling should keep as minimum

within the prescribed limit. So before paralleling, the voltage of the two

sources should be same as possible by adjusting the tap position of tap

changer.

Parallel operation of transformers

The five essential condition to be satisfied are that they should all have the

same.

Polarity

Voltage ratio

Percentage impedance

Phase rotation.

Identical vector diagram and phase displacement.

Active and reactive power transfer

The power transfer from a source to load is always depends on

the total impedance (transformer + line + generator) and the voltage angle /

load angle of the system. Here Reactive power transfer is always depends on

the magnitude of the voltage, that is always higher voltage to low voltage. The

active power transfer is always depending on the load angle / voltage angle

''δ'' irrespective of the magnitude of the voltage. So magnitude of the voltage

is depends on the voltage regulation and in turn depends on the impedance of

the system. Therefore the percentage impedance and voltage phase angle /

load angle are the determining factors of load flow from a source to a load at

remote end. The following factors determine the power transfer and thus the

current through a line.

1. Percentage impedance of transformers

2. Impedance of the line up to the load.

3. Load angle at different load centre or the phasor

displacement of voltage between source end and load end.

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Bad paralleling

Causes of bad paralleling.

1. Voltage difference at the two systems involved. This will determine

the Reactive power flow and the circulating current.

2. Network impedance up to the point of NOP closure.

3. Power system load angle.

During shut down or for load rearrangement, we have to shift Normal

Opened Point between PRY's. To avoid interruption paralleling is required. In

some paralleling cases, the circulating current increases rapidly and trips the

weaker portion. This is bad paralleling. The main causes of bad paralleling

are, (i) the loads feeding from different sources (load angle)(ii) Percentage

impedance of the transformers are different (iii ) line impedance up to the load

from the sources are different due to the difference in length .

Tap Blocking

At the time of paralleling, the tap position should be normal to all

transformers to avoid the voltage difference. The voltage difference is not

advisable for healthy paralleling. So blocking of tap is required at the tune of

paralleling. Otherwise, the voltage difference cause to produce high

circulating current and this trips the weaker portion.

One another reason for tap blocking is the tap changer is designed to

operate on load condition and not for operating on fault condition. One reason

for blocking the tap during paralleling is to avoid flow of fault current through

the tap changer while tap changing takes place.

Isolation and Earthing for Different Switchgears

Oil Circuit Breaker - Vertical isolation.

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1. Service position - OCB, connect the Bus bar to the feeder /

transformer circuit when OCB is in closed condition , the live Bus bar is

connected with the feeder / Transformer.

2. Circuit Earth Position ( CK/E )

OCB provides connection facility between feeder / transformer circuit and

earthing system (station earth) .When OCB is in closed condition , the feeder /

transformer circuit is in earthed condition.

3. Bus bar Earth Position

OCB provides connection facility between Bus bar and earthing system. When

it is in closed condition ,the Bus bar is earthed.

Vaccum Circuit Breaker - Horizontal isolation

1. Service position

VCB provided connection facility between Bus bar and Feeder / Transformer

circuit.

2. Isolated / Tested Position

This is Rack / out condition, that means disconnected from the live system.

Earth Switch- Earth switches are provided to earth the feeder /

transformer/Bus bar circuits during shut down.

Progress report on Construction section04-06-2006

Eng: Dharam

Commissioning of new I/D

substation in between 4345 I/D

Qatar Islamic Bank s/s and 9899

After proper back feeding, the

cable between the two s/s is

isolated and earthed as per

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Qatar international Islamic Bank I/D

11 325 NAJOA CAR PARK – 1- I/D

TAMCO VCB

1 L/TX – 1000 KVA

4345 – I/D –OCB

9899 I/D – VCB.

switching programme. PTW issued

to make and break (2 No)

termination for the new s/s. After

the work cancelled t he PTW. SFT

issued to HV / pressure test for the

cable between the I/D including

new s/s. P/ Test done at new I/D.

and cancelled SFT& confirmed

SW/ position. Live phasing done at

new s/s (11325- I/D).

Commissioned new s/s and local

TX.

05-06-2006

Eng. Dharam

Commissioning of new O/D

substation, Semi extensible 12603

with 1250 KVA transformer,

LABOUR CAMP –O/D in between

9935 I/D and 3828 O/D substation.

RMU is TAMCO ( SF 6 )

Rated voltage -12 KV ,

rated current – 630A, Rated short

time breaking current = 20 KA for 3

Sec

After proper back feeding, the

working portion isolated and

earthed as per switching

programme. Issued SFT to

identify, spike and color phasing

the cable. Cancel SFT & confirm

SW/P. Issued PTW to break and

make (1 No) termination and for

(1 No) straight joint for the new

substation, cancelled PTW. Issued

SFT to HV – PR / Test and

cancelled SFT & confirm SW / P.

P/T done at 9935- I/D. Live

phasing done at 9935 I/D.

Commissioned the new s/s and

after MV Voltage & phase rotation

check commissioned the local TX.

06-06-2006

Eng. Prakash

Choudary

Commissioning of (A 400) feeder at

ABU HAMUR NORTH PRY.

PRY – New SEIMEN'S VCB –

After proper isolation & back

feeding, the cable between the two

I/D is earthed. Issued SFT for

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German make.

(A400) cable – bx size.

A400 is Connecting to the 10811

SALWA RD SHML I/D ( VCB – EPE

make )

identification, spike and color

phasing the cable, cancel SFT &

confirm SW/P. Issued PTW to

make one No. ST. joint for the

cable A400 between the two I/D's

after the work cancelled PTW.

Issued SFT for P/T and cancelled

SFT confirm SW/ P. After checking

11 KV live phasing, cable A400

commissioned.

07-06-2006

Eng Nizamudeen

Commissioning of 10132 KSW- I/D

in between 4180 (O/ D) and 4160

(O/D) substation.

Commissioned the new I/D and one

local TX (1000 KVA) commissioned

after checking the existing MV

voltage & phase rotation.

Normalized the system by re

establishing NOP.

Shifted the load as per switching

programme. Isolated & Earthed the

working section at both end.

Issued SFT for identification, spike

and colour phasing. Cancelled

SFT & confirmed SW/ position.

Issued PTW for 2 Nos. straight

joint. Cancelled PTW after the

work. Issued SFT for HV P/Test.

Cancelled SFT and confirmed SW/

position. Live phasing done at new

I/D

08-06-2006 Attended Construction office work.

12-06-2006

Eng: Dharam

Replacement of RMU & ADD on

feeder switch at substation 4953

O/D

Old RMU – Merlin Gerin (SF6 )

After load shifting, CME applied at

both ends of point of isolation.

Issued PTW to break and make

the HV termination & to replace the

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Extensible type.

New RMU - LUCY (SF6 )

Extendible type

Commissioned new RMU with an

additional feeder switch.

old RMU with additional feeder

switch. After the work, cancelled

PTW. Issued SFT , cancelled SFT

& confirm SW/P.11 KV Live

phasing done at 5167 DN- 13 I/D.

13-06-2006

Eng. Nizamudeen

Replacement of Defective RMU at

10313 KR – 6 O/D and to close the

ring with spare cables of 10313 KR-

6 O/D between 9787 KHORE EAST

-5 and 10319 KHORE SOUTH O/D

After MV check and phase rotation

commissioned the s/s and TX's.

After isolation, applied CME at

both ends. SFT issued for colour

phasing. cancelled SFT , PTW

issued to make 3 Nos ( Break and

make ) termination at 10313 O/D

and for I No. Termination at 9787

O/D and also for one ST joint

between 10319 KR-9 O/D and

120313 O/D. Cancelled the PTW.

Issued SFT for HV P/Test,

Cancelled SFT& confirmed the

SW/ P. Live phasing done at

10320 I/D

14-06-2006

Eng: Mr. Imad

11 KV cable diversion between

Naeeja North PRY ( A 200 ) and

( 0534 ) OAP – 8 I/D.

VCB at Naeeja North PRY is

SEIMENS.

Live phasing done at (0534) – I/D

After load shifting and isolation,

applied CME at both ends. SFT

issued for identifying, spike and

colour phasing the cable. SFT

cancelled and PTW issued to

make 2 Nos st.joints for the cable

between Naeeja(A200) and (0534)

OAP-8 I/D Cancelled the PTW.

Issued SFT for HV P/Test,

Cancelled SFT& confirmed the

SW/ P.

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Progress report on Distribution Protection 18.06.2006

Eng. Shahul

Location- 11456 Villagio -11 I/D

ABB Make numerical relay

Replacement of SPAJ135C by

new high set SPAJ140C for L/TX's

19.06.2006 Pre commissioning test for I/D Attended magnetization test,

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With technicians

Primary injection, Trip circuit

healthy test for breakers

20.06.2006

Eng. Shahul

1.Abu Hamur North PRY

SIEMENS-SIPROTEC-7SJ61

2.Indoor substations

After fault maintenance- Setting

change for feeders

Relay setting change- as per DCC

advice

21.06.2006

With technician

1671- O/D- Industrial area

Old L/TX is 500 KVA

Setting change for L/TX (1000

KVA)

CT Ratio changing

22.06.2006

With technician

Saliya PRY A200 Tripped, Solkor

operated

Solkor decommissioning attended

25-05.2006 to

28.06.2006

NCC Attended routine activities

01.07.2006

Eng. Murali

Transmission protection

Hamad Medical City PRY

Commissioning

02.07.2006

Eng. Salim

AL SADD PRY Relay maintenance

03.07.2006

Eng. Sherrif

Learning session conducted

04.07.2006 to

06.07.2006

Transmission O&M

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Progress report (O &M)

Date Engineer Work Remark Safety22-05-06 Mr. HAKKIM

Mr. Raju

Replacement of faulty TX4 (Due to oil leak )at (9649) City Centre -1-1/D VCB – TAMCO

1.Replacement of faully TX (Due to oil leak)at an O/D substation.

2.Replacement of transformer(BOFP) by a New TX ( FSFP) at an O/D substation.

VCB – TAMCOE/S – available for each circuit consumer MV panel with ACB available and REF realy provided for MV side protection.Inter trip for HT is provided.Before restoring MV side,Checked MV voltage & Phase rotation

O/D extensible RMU ( oil ) Yorkshire type.

Semi Extensible RMU ( Oil ).Before restoring MV side checked MV voltage & phase rotation.

Operational safety as per switching programme instruction from system control engineer.After proper isolation & Earth, issued PTW for Break and make 11 KV termination.

Operational safety as per SW/ProgrammePTW issued for break and make HT termination to New TX.Operational safety as per SW/ProgrammePTW issued for break and make HT termination to New TX.

Date Engineer Work Remark Safety

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23.05.06

24.05.06

25.05.06

Mr.Rajivkumar

Mr. Hakim

Mr. Raju (Stand by Duty)

NOP shifting programme to Load DUHAIL PRYsystem operation duty.

1) Rectification of faulty cable by making straight joint& charging the cable.(Cable bitween 1036 city BANK s/s I/D and 5716 O/D )

2)Rectification of faulty cable between ( 2462 ) SH EID BIN MAD No: 3 s/s and an O/D S/S

Fault restorationSFT & PTW issued for an HT Cable between NDC,PRY & an I/D S/S

3nos1/D&5nosO/D Substation visited as a part of NOP shifting. VCB - EPE, TAMCO OCB - south wales RMU -

Tiger oil switchVCB – AGEStraight jiont fault

Third party damage

NDC, PRY visited OCB Panel,Co2 Blasters provided for safety

Operation as per system control ( DCC ) switchihng programme.Confirm supply is important in each operation.

Issue SFT for Identification, Spike& Colour phasing .Issue PTW for one termination & one No: ST joint nearer to 5716 O/D Issue SFT for spike,colour phasing the cable.Issue PTW for straight joint the cable

SFT issued for Identification,Spike&Colour phasing. Issued PTW for 2 Nos stright joint.

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27.05.06

28.05.06

29.05.06

30.05.06

Mr. Raju

Mr. Mahmood

Mr. Inose

Mr.Rajivkumar

Transformer replacement ( BOFP ) -1000 KVA By new one at 725 I/D

11 KV OHL – Maintenance-Redial circuit from ( 9757 ) new Al Qayan O/D ( Al Khore lnd.Area) Replacing ABS (S-144 ) , (S- 145) & 8 Nos. LA installation at Pole box and PMT

Cable fault Rectification

1.Replacemant of faulty O/D substation (package type) at 4362 O/D – HV P/Test pending

2. SF6 gas pressure Low -Refilling at 5484 O/D Substation ( Lucy SF6 )

Ray Rolle OCB MV Voltage & Phase rotation checked before MV restoration

RMU at O/D s/s is SF6 ( TAMCO )

Ray Roll OCB

HV Pressure Test done for new O/D substation.Live phasing done at 2569 1/D. Before the Live phsing Existing and new phase rotation checked at 2420 O/D.

Checked 11 KV line phasing at 1/D

PTW issued for Break & make 1 No.HT termination to loop the transformer.

After isolation &Earth issued PTW to the competent person ( Before issueing PTW, test OHL,if Dead,Apply Portable Earth )

Issued SFT for colour phasing the HT cableIssued PTW for making 2 No Stright joint for the faulty cable.

Issued SFT for HV P/Test for the new O/D subatation.Issued PTW for refilling SF6 Gas at 5484 O/D substation.Issued PTW for MV termination.

77

31.05.06

01.06.06

Mr. Hakkim 1.Fault rectification of an HT cable between SH . ABDULLA FARM-1 1/D and pole Box Pole Box termination faulty.

2.Fault restorationKHORE A300- tripped at an 1/D substation, the OHL lodial line ( with two TEE off -circuit ) Total supply failure.Indication - stand by E/F flag ON at PRY and alarm initiated at NCC for both TX

ABU HAMUR WORK SHOP VISIT

2) Fault restoration Industrial area 1671- MI 1/D Substation, one TX ( 500KVA ) tripped on over loadTX -replaced by ( 1000 KV )

Over head line involved

1/D – E/F relay operated EFI flagged at one pole Box(Radial TEE-off circuit )

Hands on training on different types of switches ( Oil & SF6 ), VCB & OCB'S

Indication R&B O/C

Issued SFT for colour phasing the cable.Tested the OHL, found Dead then applied the protable Earth.Issued PTW for one No. Jumper connection and for raise the Pole box. Noticed all indication and after proper petrolling found that the earth wire(1 span) snapped in the radial TEE-off circuit.Isolated & earthed the faulty portion. Then charged the healthy circuit from the 1/ D (All Relays and indications resetted.Kept the relay setting TSM minimum for test charging.).PTW issued for fault rectification.Issued PTWfor transformer replacement.Informed protection department to change the relay settings.

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