dewa testing procedure (1)

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Transmission Commissioning Department 1/27

Transmission Commissioning Department

Protection Test Procedure(For TCD Scope of Work)


Index

SerialNo

Description PageNo

1 CT Test Procedures 32 VT Test Procedures 113 Relays Definitions 154 Test Setup for Auxiliary / Trip Relays 165 Procedure for Auxiliary Relay Tests 176 Procedure for Trip Relay Tests 217 Procedure for Meter Tests 238 Relay wiring diagrams 24


Testing of Current Transformers (CTs)

1. General Checks:

The following general checks are performed before proceeding with the CT Test:

GENERAL VISUAL INSPECTION FOR ANY DAMAGES/ PROPER MOUNTING NAME PLATE VERIFICATION WITH DRAWING TIGHTNESS CHECK AT CT SEC. TERMINALS TIGHTNESS CHECK AT CT SEC. TB LV COMPARTMENT/ LCCPOSTION OF P1 - TOWARDS BUS/FEEDER STAR FORMATION - S1/S2 COLOUR CODED CYLINDERS USED IN TERMINALS FOR TESTS

EARTHING OF STAR FORMATION The IEC Standard applicable is 60044-1.


1.1 Precautions:1.1.1 follow the test sequence of Test Formats. It is important to perform

mag. Curve test after winding resistance measurement and polarity test.

1.1.2 Never keep the CT Secondary open while injecting current in the primary of CT. Failure to observe this precaution would result in fatal injury and/or CT Failure.

1.1.3 There is risk of electric shock during CT Tests. Observe necessary safety precautions.

1.2 Test Instruments required: 1.2.1 Insulation Tester 1.2.2 Low Resistance Ohmmeter 1.2.3 Polarity Kit 1.2.4 Mag. Curve Set Up (Variac, Step up Transformer, Multimeters, Test Leads 1.2.5 Primary Injection Kit 1.2.6 Tong Tester

2. Insulation Resistance Test:

2.1 This test is performed to confirm that no insulation detoriation has taken place during transportation or installation. 2.2 The insulation resistance is measured between core to earth and across the core as appropriate (Primary to secondary). The duration of test can be few second till a reasonable good value is obtained. 2.3 Ambient temperature must be recorded with a calibrated temperature meter. 2.4 Generally any IR Value above 100M: is acceptable as there is no IEC Standard

Criteria for this test. The CT Test Results with low IR Value must be investigated for insulation damage or dust contamination on terminals.

Example:IR Values shall be measured up CT terminal blocks .


3. Winding Resistance Measurement: The CT Secondary Winding resistance is measured in ohms and corrected to 75qC. Temperature - t 0C and Humidity

R Phase Y Phase B Phase CTTERMINLAS

Ter.Block

R at t0C (

R at 750C (

R at t0 C (

R at 750C (

R at t0 C (

R at 750 C (

T7L ( 1S1 - 1S2)

XC

Resistance at 750 C = R t ( 1 + 0.00393 ( 75 t ) )

4. Polarity Test

The CT Polarity Test is performed to verify that the primary and secondary polarity markings are correct. Any wrong polarity will result in wrong measurement and protection mal-function. The positive and Negative Supply of low DC Voltage (9V) is applied to P1 and P2 (Primary Terminals) of the CT respectively. The Galvanometer positive and negative terminals are connected to S1 and S2 (Secondary Terminals) of CT, should give a forward deflection. Reverse deflection indicates a wrong polarity.

Refer to below sketch for test set up.

DC V applied R Phase Y Phase

BPhase

T7L Sec. to Primary 2.5kVT7L1 Sec. to Primary 2.5kVT8L Sec. to Primary 2.5kVT8L1 Sec. to Primary 2.5kVT7L to T7L/1+T8L+T8L/1+Earth 500VT7L/1 to T7L+T8L+T8L/1+Earth 500VT8L to T7L+T7L1+T8L/1+Earth 500VT8L/1 to T7L+T7L1+T8L+Earth 500V


POLARITY CHECKS. R Phase Y Phase B Phase

CT Terminals At CT Ter. Blocks in LV/LCC Comp

At CT Ter. Blocks in LV/ LCC Comp

At CT Ter. Blocks in LV/ LCC Comp

(1S1 - 1S2) (2S1 - 2S2) (3S1 - 3S2) (4S1 - 4S2)

5. Test Procedure for Magnetization Curve of Current Transformer:

5.1 Objective of the Test: To identify the knee-point Voltage (Vk) of a Current Transformer and to verify whether the Mag. Curve Characteristics are matching with relay application requirements.

5.2 Test Equipment:

The test is carried out with a variable voltage applied to the secondary of the current transformer. The test voltage can be obtained from a variable voltage source or through a variable autotransformer. Voltmeter and Ammeter are required to measure the voltage and current respectively in the secondary circuit.

5.3 Principle of Operation:

The core of the current transformer gets magnetized due the primary current flowing in the circuit and this helps in faithful reproduction of the quantity in the secondary circuit. However, it is a property of the magnetic core to get saturated, due to high value of currents.


In case of core saturation, the CT will not reproduce the primary current into the exact secondary current. In some application where primary protection relays are connected, the CT has to remain unsaturated up to a desired value of primary current. This property of the CT is designated with a parameter called as Knee-point voltage.

Knee-point voltage of the current transformer is defined as the voltage at which 10% increase in secondary voltage results in 50% increase in the magnetization current, with the other windings (i.e., primary & test) in open circuited condition.

The objective of this test is to plot the magnetization curve of the CT there by, locating the knee-point voltage, Vk. This value of Vk is compared with the manufacturers design value.

5.4 Test Procedure: 5.4.1 Visual Check: Ensure that the surface of the transformer is clean and the wires properly terminated.

Drawings checks for star point formation / ferrules /shorting link location.

The secondary circuit earthing lead is temporarily isolated from the ground.

5.4.4 Ensure that the primary circuit is open ie., the circuit breaker in the primary circuit is kept open.

5.4.5 A typical test connection for a magnetization curve of current transformer is shown below figure:

Fig.: Typical test connection for CT Mag. Curve test.


5.4.6 Voltage is applied in the secondary core of the CT under test. The voltage is slowly increased and the current (mA) in the secondary is noted.

5.4.7 This process is continued until the core saturates. The core saturation in indicated by steep increase in the secondary current for a marginal increase in the secondary voltage.

5.4.8 The values are plotted in a log scale and the knee-point voltage obtained. The obtained value of Vk should be equal to or greater than the design value specified on the CT nameplate.

5.4.9 Ensure a gradual increase or decrease of the secondary voltage during the test, as a sudden variation in the voltage may produce dangerous flux variation which may damage the secondary insulation.

5.4.10 A typical CT mag curve and Vk are shown in fig below. 5.4.11 The same procedure is repeated for the other phase CTs.5.4.12 After completion of the test, ensure that all the CT secondary connections are restored

back.

MAGNETIZING CURVES FOR Vk.

Recored the test results in the following table:


Frequency of supply Hz Function:Magnetizing Current measured in mA

CO

RE

Rat

io

Term

inal

PH Sec. Wdg. ResistanceAt 750C V

at 1

A

R

Y

B

5.5 Result:

This test establishes the actual value of Vk of the CT core. Also this test establishes that correct core is used for the required application and also ensures that there is no mix-up of cores.

5.6 Ratio Test

The ratio check is carried out by injecting current into the primary of CT and measuring the secondary current. The results must be within the accuracy limits specified in the name plate of CT.This measured ratio should match with ratio specified in the CT Nameplate.

Refer to the below figure for Test Setup.


Record the test results in the following table:

R Phase Y Phase B Phase

CO

RE

Rat

io

Pri-Amps Sec-Amps Pri-Amps Sec-Amps Pri-Amps Sec-Amps

T7L

4

00 /

1


Testing of Voltage Transformers (VTs)

1. General Checks:

The following general checks are performed before proceeding with the VT Test:


GENERAL VISUAL INSPECTION

NAME PLATE

TIGHTNESS OF CONNECTIONS AT VT SEC. TERMINALS TIGHTNESS OF CONNECTIONS AT VT SEC. TERMINAL BLOCKS EARTHING OF PRIMARY NEUTRAL TERMINAL SECONDARY EARTHING CORE1/CORE2CONFIRMATION OF RATING OF FUSES IN VT TERMINAL BOX AS SPECIFIED IN DRAWINGS

SINGLE POINT EARTHINGFERRULES MATCHING WITH DRAWINGCOLOUR CODED CYLINDERS USED IN TERMINALS FOR TESTS


The IEC Standard applicable is 60044-2.

2. Insulation resistance Test:

This test is performed to confirm that no insulation detoriation has taken place during transportation or installation. The insulation resistance is measured between core to earth and across the core as appropriate. The reasonable duration of test can be 5 seconds. Generally any IR Value above 100M: is acceptable as there is no IEC Standard Criteria for this test. The VT Test Results with low IR Value must be investigated for insulation damage or dust contamination on terminals. Confirm Isolation of links of VT Terminal Blocks. Confirm isolation Primary neutral earthingTime duration of test voltage applied 5.. Secs. Ambient Temperature Humidity

DCVoltageApplied


Primary to Earth 2.5kVPrimary to Sec. Core 1 2.5kV

Sec. Core 1 to Earth 500V

3. Winding Resistance Measurement:The Primary Winding Resistance is measured in k:. It is normally measured with a Digital Multimeter. The secondary winding resistance is measured generally in milli:. It is normally measured with a low resistance Ohmmeter. There are no specific criteria for passing the test results. The results (at 75qC) must be close to the factory test values by r 10%.

Ambient Temperature - t 0C

CORE R Phase Y Phase B Phase

R at t0 C (

R at 750C (

R at t0 C (

R at 750C (

R at t0 C (

R at 750C (

Primary

Seconday

Resistance at 750 C = R t ( 1 + 0.00393 ( 75 t )


4. Polarity Test:

The VT Polarity Test is performed to verify that the primary and secondary polarity markings are correct. Any wrong polarity will result in wrong measurement and protection mal-function. The positive and Negative Supply of low DC Voltage is applied to P1 (or terminal A in the sketch) and P2 (or terminal N in the sketch) , the Primary Terminals of the VT respectively. The Galvanometer positive and negative terminals are connected to terminal a and terminal b, the Secondary Terminals of VT, should give a forward deflection.

The test results must be recorded in the format given below:

R PHASE Y Phase B Phase

VTAt VT Sec.Terminals

At VT Ter.Blocks

At VT Sec.Terminals

At VT Ter.Blocks

At VT Sec.Terminals

At VT Ter. Blocks

Core 1

5. Magnetizing Current Measurement

The magnetizing current must be measured and recorded in the below format.There are no specific criteria for passing this test. The results may be compared with factory values (if available).

6. Ratio Test

The ratio of a VT is checked out by applying voltage to the primary winding and measuring the voltage across the secondary winding. The measured ratio should match with ratio specified in the CT Nameplate

The ratio error must be calculated and it is defined as:

(Kn Vs) X 100% Vp


Where:

Kn is the nominal ratio Vp is the primary voltage Vs is the secondary voltage The error must be within limits specified in the nameplate.

Record the test results in the following table:

R Phase-Neutral

Y Phase- Neutral

B Phase- NeutralCore Pri-

VoltsSec-Volts

Pri-Volts

Sec-Volts

Pri-Volts

Sec-Volts

Core1Core2


RELAYS DEFININTIONS

DefinitionsAuxiliary relayAn electrical relay energized via the contacts of another relay for example an overcurrent relay for the purpose of providing higher rated contacts or introducing a time delay.

Self Reset RelayThe contact operates when the voltage is applied and resets when the voltage is removed.

Hand or Electrical Reset RelaysIn these relays, the contact remains operated condition even after the voltage is removed. The relay can be reset either by hand or by an auxiliary electromagnetic element.

Pick-upA relay picks up when it changes from the unenergized position to energized position.

Drop-outA relay drops out when it changes from the energized position to un-energized position.

Operating TimeWith a relay de-energized and in its initial condition, the time which elapses between the application of a characteristic quantity (e.g., voltage) and the instant the relay operates.

Resetting or Drop-out TimeWith a relay energized and in operated condition, the time which elapses between the removal of the characteristic quantity (e.g., voltage) and the instant the relay resets (de-energizes)Make ContactA make contact closes when the relay picks up.

Break ContactA Break Contact opens when the relay picks up.


Test Set Up for Auxiliary / Trip Relay Tests


Test Procedure for Auxiliary Relay

1. General

1.1 For random test contractor has to complete 100% internal testing and test reports must be ready before starting random test.

1.2 Get information from contractor about problems and defects noticed during internal tests.

1.3 Check the relay datas (type, model, and contact details) with drawings and test report.

1.4 Check the drawings for output contact configuration and function with reference sheets (e.g., Z sheet of drawings).

1.5 Select the random relays (20% of total relays). 1.6 Check IR value with 500 V Megger with respect to body/case. 1.7 Check the test setup then start the voltage injection slowly and linearly when

relay changes the status record. Record the current and voltage at the time of pickup or drop off. (Refer the test setup attach).

1.8 Compare the operating voltage and operating current with technical specification.

1.9 Follow the test sequence in the test formats. 1.10 Check the operating time of the relay (use the contact to stop the timer which is

used for alarm). By injecting 0V to rated voltage. 1.11 Check the resetting voltage, current and operating, resetting time for relay. By

reducing the voltage from 110v to 0V or 110V to reference voltage according to manufacturer recommendations. The resetting (drop-off) time must be as per manufacturers specification.

1.12 Ensures that output contact resistance, make, and brake and change over contact. Contact resistance must be less than 1 ohm.

1.13 Check the wiring and other data on at LV / Relay panels such as label, Relay Identification etc.


Test Format (Typical) for Supply Supervision RelayRelay Data.

Relay Type Aux DC Supply Model No. MVAA11

General Inspection and Checks.

i. Correctness of Installation and wiring. ii. Earthing connection for Relay case to Earth Bar

iii. IR of relay circuit & associated wiring to earth (500V Megger) iv. Operation of Output contacts v. Operation of Mechanical Flag and Resetting arm vi Sr.No. on Modules, Case and Cover Identical

No. of NO Contacts - v Contact Configuration No. of NC Contacts - Relay Test Results.

Currentat 110 Vm A

Timings at Rated Voltage

OperationatPick Up Drop OFF RelayDesignation &

Sr No.

Volts mA Volts m A

OperatetimemSec

Resettime(msec)

88V 150V

Operating time at 110V DC- < 25 mSec.

Note:Slight chattering at the time of pick up may be acceptable. There should not be any chattering within the operating range of the relay rated voltage.


Test Format (Typical) for Trip Circuit Supervision Relay

Relay Data. Relay Type Aux DC Supply Model No. MVAX31

General Inspection and Checks. i. Correctness of Installation and wiring. ii. Earthing connection for Relay case to Earth Bar

iii. IR of relay circuit & associated wiring to earth (500V Megger)

iv. Operation of Output contacts & Contact Resistancev. Operation of Mechanical Flag and Resetting arm vi Sr.No. on Modules, Case and Cover Identical

No. of NO Contacts vii Contact configuration No. of NC Contacts Relay Test Results.

PICK UP DROP OFF RelayDesignation & Sr. No.

COIL

V mA V mA

Currentat 110V mA

OperatingTimeinmSec.

Resettime m Sec at 110V

ResettingTime in mSec.(C+A)/(C+B)

C 27-28A13-14B 21-22C 27-28A13-14B 21-22

Expected Operating Time < 70 msec. ; Resetting Time > 400 msecResetting time (C+A) or (C+B) )


Test Format (Typical) for Voltage Supervision Relay

Relay Data. Relay Type Rating of relay Model No. Relay

DesignationMVAP22

General Inspection and Checks. i. Correctness of Installation and wiring. ii. Earthing connection for Relay case to Earth Bar

iii. IR of relay circuit & associated wiring to earth (500V Megger) iv. Operation of Output contacts v. Operation of Mechanical Flag and Resetting arm vi Sr.No. on Modules, Case and Cover Identical vII Contact Configuration No. of CO Contacts 3

Relay Test Results. Apply 3 phases voltage to the relay and check relay operation

1 Check Phase Rotation 2 Apply 80% of Vn and check voltage on terminals: 15,16, 22

23 - 15 25 - 16 3 Check Phasing terminals 27 - 22

4 With R Phase removed, apply 80 % of Vn and check across terminals 16-22

5 With R Phase restored, apply 125 % of Vn and check across terminals: 15, 16, 22 6 Test (same as 4) with Y Phase 7 Test (same as 5) with Y Phase 8 Test (same as 4) with B Phase 9 Test (same as 5) with B Phase

10 Check rated Voltage Vn on terminals: 15, 16, 22 (Inject voltage at: 17 18 24)

17 - 15 18 - 16 11 Check Phasing Terminals 24 - 22

12 Check for fuse failure operation for R, Y, B Phase Relay operation checked by reducing one phase voltage only

13Operates approximately 50% of rated voltage


Test Procedure for Trip Relays

1. General

1.1 For random test contractor has to complete 100% internal testing and test reports must be ready before starting random test.

1.2 Get information from contractor about problems and defects during internal tests. 1.3 Check the relay datas (type, model, and contact details) with drawings and test report. 1.4 Check the drawings for output contact configuration and function with reference sheets

(compare Z sheet). 1.5 Select the random relays (20% of total relays). 1.6 Check IR value with 500 V Megger with respect to body/case. 1.7 Check the test setup then start the voltage injection slowly and linearly when relay

changes the status record. Record the current and voltage at the time of pickup or drop off. (Refer to the test setup).

1.8 Compare the operating voltage and operating current with technical specification of relay manufacturer.

1.9 Check the current at 110 V which must be zero or very low value (confirm cut-off or economizer function of the relay)

1.10 Zero (0) or low current as per specification of the manufacturer if the relay is high burden. Low burden relays check the technical specification.

1.11 Check the operating time of the relay (use the contact to stop the timer which is used for tripping).

1.12 The expected operating time is 8 ms for AREAVA Trip relays. ( at Rated Voltage) 1.13 The expected operating time is 10 ms for VA Tech Trip relays. ( at Rated Voltage) 1.14 Check the resetting voltage, current and operating, resetting time for relay has reset

coil or self reset trip relays. Compare the test results with technical specification. 1.15 Confirm that the cut-off contact is present in both trip coil & Reset coil. 1.16 Confirm minimum one spare NO contact available. 1.17 Check the capacitance discharge test for High Burden trip relay. Relay should not trip.

with Capacitor connected (Refer test setup). 1.18 For Areva relays there is a shorting across 22 and 24 for high burden application. 1.19 First charge the capacitor to 150V 1.20 Discharge the capacitor through relay. Relay should not operate. 1.21 Ensures that output contact resistance, make, and brake and change over contact.

Contact resistance must be less than 1 ohm. 1.22 Check the wiring and other data on at LV Compartment/ Relay panels such as label,

Relay Identification etc. 1.23 During pick up and drop off test the capacitor (of test setup) circuit must be in OFF

Condition.1.24 Capacitor must be connected to correct polarity during capacitor discharge test.


Test Format (Typical) for a Trip Relay

Relay Data. Relay Type Aux DC Supply Model No. MVAJ 055 General Inspection and checks. i. Correctness of Installation and wiring. ii. Earthing connection for Relay case to Earth Bar

iii. IR of relay circuit & associated wiring to earth (500V Megger)

iv. Operation of Output contacts & Contact Resistancev. Operation of Mechanical Flag and Resetting arm vi Sr.No. On Modules, Case and Cover Identical

No. of NO Contacts 4v Contact configuration

No. of NC Contacts 1Relay Test Results

Operating Coil PICK UP

Reset coilPICK UP

Operating Time in mSec. at Voltage Relay Designation

Sr. No. VOLTS mA

VOLTS mA

Currentat 110V mA 110V 66 V 150 V

Capacitor Discharge Withstand test: Operation on Discharge of 150 Volts with 10 F Capacitor Operated Not Operated. If operated at 150 V, The discharge voltage below 150 V at which relay not operated must be recorded.

Mechanical Reset Test: Reset the relay with front cover closed and check all contacts resetting properly. Operating time at 110V DC < 8 mSec.

Note:1. The reset test is not applicable for Hand reset relays. 2. There would be chattering at the time of pick up. This is acceptable. There should not

be any chattering within the operating range of the relay rated voltage.


Testing of Meters

1. Objective:

The objective of test is to verify whether the measurement is within the accuracy class specified by the manufacturer and DEWA.

2. General:

Verify the nameplate details (e.g., range, CT/VT Ratio, Accuracy Class etc are matching with the specification given in the approved drawings).

3. Calibration

3.1 Connect the meter to be tested (e.g., a 0 1200A, CTR 1000/1A Ammeter) to the test kit. 3.2 Inject current till the meter dial under test reads 1200A. Record it in the test format Actual

Reading.3.3 Note down the current injected in the Input current. (e.g. 0.99A) 3.4 Calculate the expected current by multiplying the input current with CT Ratio. It would be

990A (for this example). Record this value in the Expected Current. 3.5 Calculate the Percentage Error with the following equation:

Actual Reading Expected Reading X 100% Full Scale Reading 3.6 Record 3 to 4 Readings (e.g., at 20%, 50%, 75%, 100% and Full Scale of readings).

AMMETER TYPE: ACCURACY CLASS: RATING:

CT RATIO : FULL SCALE READING :

FEEDERNO.

AMMETER SR NO.

INPUTCURRENT(mA)

EXPECTEDREADING (A)

ACTUALREADING(A) %ERROR


Wiring diagram: Typical Trip Circuit Diagrams


Wiring diagram: Typical Trip Circuit Supervision Relay Type MVAX 31


Wiring Diagram: Typical Trip Relay Type MVAJ055


Wiring Diagram: Typical Voltage Supervision Relay Type MVAP22

Diagrams: Courtesy Areva

dewa testing procedure (1)

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