line protection avsramesh 28 sep 2006

8/6/2019 Line Protection AVSRamesh 28 Sep 2006

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Protective RelaysAVS RameshDy.Manager (Operation Services)POWERGRID


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One and Half Breaker Scheme

Ckt-1 Ckt-2

Bus-1

Bus-2

21


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Distance Protection

Distance Protection schemes shall have

Three independent zones

Separate measurements for all Phase to Phase &Phase to ground faults.

Single and three pole tripping capability.

Directional characteristics for Zone-1, Zone-2 and

Zone-3. Capability of operation for close up three phase and

switch on to faults.

Adjustable characteristic angle to match line angle.


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Distance ProtectionDistance Protection schemes shall have

Accuracy of better than or equal to 5% of set value for

reach measurement in Zone-1 & Better than equal to10% of set value for Zone-2 & Zone-3.

Accuracy of better than or equal to 5% of set value

for time measurement of Zone-2 & Zone-3.

Power Swing detection feature for selective blocking,

as required.

Suitable fuse failure protection to monitor all types of

fuse failure and block the protection.


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Distance Protection - Setting criteria

Reach Setting:

Zone-1 : To cover 80-85% of protected line section.

Zone-2 : To cover minimum 150% of length ofprincipal line section.

Zone-3 : To cover 120% of principal section plusadjacent longest section.


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Zone-1Zone-2

Zone-3

A B C85%

150%

ZAB + 120%



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Time setting:

Zone-1 : Instantaneous Zone-2 : 0.3 sec,0.5 sec

(For short line followed by long line)

Zone-3 : 1.0 sec.



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Power Swing

LoadArea

X

R

Z1

Z2

Z3

RecoverableSwing


10/66

Phase Comparison Protection

Current Phase comparison type

Suitable for operation without PLCC

High sensitivity for all types of faults

Capable of single and three pole tripping


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Phase Comparison Relay(Through fault)

A B

A

B

A+B

B

A

A+BNo Trip No Trip


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Phase Comparison Relay(In-Zone fault)

A B

A

B

A+B

B

A

A+BTrip Trip


13/66

Phase Comparison Protection shall be

Un-Affected by :

Heavy load transfer Power swings

CT saturation

CT Phase errors Propagation delays

Capacitance current


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Technology comparison for Protective Relays

Sl.No.

Subject Electro-mechanical

Static/Electronic

Numerical

1. MeasuringElements/Hardware

Induction disc,Electromagnets, Induction cup,Balance beam

Discrete R, L, C,Transistors,

Analogue ICs,Comparators

Microprocessors, Digital ICs,Digital SignalProcessors

2. Construction

size

Bulky Modular,

Compact

Most compact

3. Parametersetting

Plug setting,Dial setting

Thumb wheel,Potentiometers,Dual In Lineswitches

Keypad forNumericalvalues


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Technology comparison for Protective Relays

continued

Sl.

No.

Subject Electro-

mechanical

Static/

Electronic

Numerical

4. CT Loading/

burden

8-10 VA 1 VA < 0.5 VA

5. Self

monitoring

No Yes

.Hardware

partially

.Powersupply

Yes

.Hardware

.Power supply

.Output relays

.Software

.CT, PT,Ckts

6. Temperature

stability

Yes No Yes


16/66

Technology comparison for Protective

Relays continued

Sl.

No.

Subject Electro-

mechanical

Static/

Electronic

Numerical

7. Vibration

proof

No Yes Yes

8. Harmonic

immunity

No Possible through

analog

filtering

Yes, digital

filtering

incorporated

9. Calibration Frequently

required as

settings drift

due to ageing

Required as

settings drift

due to ageing

Not required as

settings are

stored in memory

in digital format


17/66

Technology comparison for Protective

Relays continued

Sl.No.


Static/Electronic

Numerical

10. Auxilliarysupply

Required Required Required

11. Electromagnetic/electrostatic

/HF

disturbance

Immune Susceptible Immune

12. Multiplecharacteristics

Not possible Not possible Possible

13. Integratedprotective

functions



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Technology comparison for ProtectiveRelays continued

Sl.No.


Static/Electronic

Numerical

14. Range of settings Limited Wide Wide

15. Operational valueindication

Not possible Possible Possible

16. Fault disturbancerecording


17. Digitalcommunicationport

Not possible Not available Available

18. Commissioningsupport from relay

No No Yes


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Analog filter

Sample & Hold

Multiplexer

Signal Input

A/D converter

Digital Filter Protn. algorithm

Relay logic

Trip /alarm

Numerical Distance Relay


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Numeric Protection Sample and hold amplifier


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Numeric Protection

Signal Sampling principle


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Numeric Protection

Typical numeric relay hardware


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Numeric Protection

Distance relay model ofTransmission Line


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Numeric Protection

Impedance measuring algorithm

Vr = Rir + L (dir /dt) -------------- (1)

where

R = Series ResistanceL = Inductance

vr = Relaying voltage

ir = Relaying current

The current derivative of equation (1) can be written as

Vr = Rir + L ir where ir = (dir/dt)


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Numeric Protection

Impedance measuring algorithm ..contd.

To solve for two unknowns, two equations are required..

Hence two sets of relay voltages, currents and currentderivatives are utilised.

Vr1 = Rir1 + L ir1Vr2 = Rir2 + L ir2

Combining the above two equations,

R = (Vr1ir2 - Vr2 ir1)/(ir1ir2 - ir2 ir1)

L = (Vr2 ir1 - Vr1ir2 ) / (ir1ir2 - ir2 ir1 )

For convenience, let D = (ir1ir2 - ir2 ir1 )


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Numeric Protection

Impedance measuring algorithm ..contd

The apparent resistance and reactance presented to the relaymay be calculated as follows:

R x D = (Vr1ir2 - Vr2 ir1) and

X x D = LD = (Vr2 ir - Vr1ir2 )

where is power system frequency and X is reactance


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Numeric Protection Impedance measuring

algorithm ..Time spaced solution


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Numeric Protection Impedance

measuring algorithm ..current derivative


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Numeric Protection Quadrilateral

characteristic and counting strategy


30/66

Auto Reclosing scheme Single Phase and /or three Phase reclosing facilities

Continuously variable single phase and three phasedead time.

Continuously variable reclaim time

Facility of selecting single phase / three phase /Single & three phase auto reclosure/ Non-autoreclosure modes.

Facility for selecting check synchronising or dead linecharging features.

Sequential reclosing facility of breakers in multiplebreaker arrangement.


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Auto Reclosing scheme Setting criteria of auto reclosure

Dead time : 1 sec

Reclaim time : 25 Sec

Protections which shall start autoreclosing

Main-I Protection

Main-II Protection


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Y Y

B B

R R

Y Y

B B

R R

Y Y

B B

R R

I II

III

Auto Reclosure Sequence


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Auto Reclosing scheme Protections which block auto reclosing:

LBB

Line reactor Protection Over Voltage Protection

Bus Bar Protection

Zone-2/3 of distance Protection

Circuit breaker problem

Carrier fail

Receipt of DirectTrip signal.


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Over Voltage Protection Two stages

High drop off to pick up ratio.

Adjustable setting range for voltage and time.

Low set stage and shall monitor any onePhase Phase voltage and shall have

associated timer. High set stage shall monitor all three voltage

and shall have associated timer.


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59

Vn

1.1 Vn

CVT


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Over Voltage Protection Over Voltage Protection shall be

connected to:

Trip connected line breaker(s)

Start LBB

Block auto reclose

Send direct trip command


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Over Voltage Protection-Settings

Low set stage at110% with typical timedelay of 5 seconds.

High set stage at150% with time delayof100mSec


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Transformer Protection Transformer differential protection

Restricted earth fault protection

Over fluxing protection

Back up directional Over current &Earth fault protection on HV side

Back up directional Over current &Earth fault protection on IV side


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Transformer Differential Protection

R

Y

B

RYB


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Transformer Protection Protections & Monitors built-in to transformer

Buchholz relay

Winding temperature Oil temperature

Oil level

Pressure relief

Fire protection

Protection of tertiary winding

Over load alarm


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Differential Protection Triple pole feature with individual phase

indication

Unrestrained instantaneous high set O/C unitswhich should not operate during in rush.

Adjustable for multi bias setting

Second harmonic or other inrush proof feature.

One bias winding per phase and per CT input

An adjustable operating current


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Bias

1.0 2.0 3.0 4.0

0.2

1.0

2.0

3.0

Through Bias Current

Operate

Not-Operate


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Restricted earth fault protection

64


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Over Fluxing Protection Phase to Phase connected

Operating on the principle of measurement of

voltage to frequency ratio. Provided with inverse time characteristics

compatible with transformer over fluxing.

Provided with independent alarm with a

definite time delay at value of V/F between100% to 130% of rated value.

Having high reset ratio of 98% or better.


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51

51

220KV

400/220 KVTransformer

A

B

Back-Up Over currentprotection

400KV


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Over Load alarm Single Pole feature

Definite time over current feature

Continuously variable current range of50-200% of rated current andcontinuously variable timer setting

range of1

to10

Secs. Drop off to Pick up ratio of 95% or

better.


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Reactor Protection Differential Protection

Restricted earth fault Protection

Reactor Back-up protection Buchholz relay

Winding temperature

Oil Temperature

Pressure relief

Oil Level

Fire Protection


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R

Y

B B

Y

R

Shunt Reactor


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R

Y

B B

Y

R

Single line to Ground Fault


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Differential Protection -

Reactor Operating current sensitivity of atleast

10% of nominal current

Tuned to system frequency Suitable non-linear resistors to limit peak

voltage during in-zone faults

High or low impedance principle


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Differential Protection -

Reactor

Operating current sensitivity of atleast

10% of nominal current

Tuned to system frequency

Suitable non-linear resistors to limit peak

voltage during in-zone faults

High or low impedance principle


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Backup Protection-Reactor Either Impedance type or definite time O/C & E/F

type

Impedance type reactor back up Protection shall be

Triple Pole type

Single step Polarised MHO or impedance distancerelay

Having characteristic angle between 60 80

degree. Provided with adjustable definite time delay relay

Provided with suitable range for covering 60% ofreactor impedance.


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Bus Bar Protection

87

Ckt-1Ckt-2

87Main Zone

Check Zone

RYB

N

RY

B


56/66

Bus Bar Protection 3 Phase type and operate selectively for each

bus bar section

Operating on differential principle and shallprovide independent zones of protection foreach bus.

Provided with Zone indication

Stable for through fault condition Provided with continuous supervision for CT

secondaries.


57/66

Local Breaker Backup

protection Short operation and drop-off times

Three phase current elements with facility

for phase wise initiation Current setting range such that the relay can

be set at minimum 200mA (for line) and 50mA (for generator) for 1Amp CT secondary

Associated timer with adjustable setting.


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Distance to Fault locator Shall be electronic or microprocessor

based

On line type

Shall be suitable for CB operation of2cycles

Built-in display(KM)

3% accuracy for all type of faults


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Distance to Fault locator Accuracy shall not be affected by Remote end

infeed

Dc component in fault current Arc resistance

CVT transients

Mutual compensation facility

Based on traveling wave generated by fault


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Event Logger To record the state of switchyard

equipments and relays.

To record the occurrence of alarms.

To record changes in digital inputs

To record switching of primary plant

within sub-station.


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Event Logger Time synchronised with GPS clock

Permissible drift +/- 0.5seconds/day

Print out of current alarm and plant status available on request.

To entry of date and time from key board.

Programmability at site. Shall record 40 changes in 10mSec interval.


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Disturbance Recorder To understand behavior of the Power

network before or after any

disturbance.

Useful info in planning of newinstallations.

For further improvement in theequipment


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Disturbance Recorder-Functions Records instantaneous values of V, I, In and open delta

voltage.

Status of relay contacts and CB during disturbance. Requirement

Recoding capacity-8 analog + 16 digital.

Memory 5 sec

Min. Pre fault 160mSec Post Fault 2sec- min , not less than 5sec.


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Disturbance Recorder-TriggersAny digital signal triggering.

Analog triggering by threshold levels.

Trigger selection of over/under levelsshould be possible.

Time tagging:

Built-in real time clock. Drift of the clock shall not be more than

0.5sec per day.


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Disturbance Recorder Sampling rate : 1 Khz

Recording : 5Hz to 250Hz.

Special requirement: Sync. With GPS

16Analog + 32 digital for D/C lines

DR + FL

If DR is part of Numerical Protection,externalbinary input should be possible.


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line protection avsramesh 28 sep 2006

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