NAME OF TEST:
GIS SF6 Gas Purity Check, GIS SF6 Gas Dew Point Measurement.
OBJECTIVE OF THE TEST:
To verify that the SF6 gas content of all chambers is within the given limit, Using a dew point meter, confirm that the moisture content in SF6 gas is less than normal value for all gas zones of the newly assembled GIS.
STANDARD/SPECIFICATION REFERENCE OF THE TEST: IEC 62271, IEC 62271-203,
IEC 60694.
PROCEDURE OF TEST:
Connect the SF6 gas content measuring device to each chamber as per the diagram.
Switch on the device. Open the NC valve slowly to allow the gas from the chamber into the device, wait for the reading to be stabilized and record the reading Connect the dew point meter to the different zones as per the following figure. SF6 gas shall be allowed to pass through the instrument as per the recommended testing procedure. (Refer the instructions of the instrument manufacturer). Dew point shall be converted to the PPM as per the standard conversion graph.
ACCEPTANCE CRITERIA:
The SF6 gas content in each chamber shall be more than 95%, The moisture content shall be less than 1)150ppm for CB chamber 2)500ppm for all other chambers of the GIS
NAME OF TEST:
GIS SF6 Density Monitor Calibration (Alarm contact setting checks
OBJECTIVE OF THE TEST:
To verify that the SF6 gas density monitors work correctly and within the given criteria.
STANDARD/SPECIFICATION REFERENCE OF THE TEST: IEC 62271-203
PROCEDURE OF TEST:
Density meter shall be calibrated through out its range from 5 bar to the maximum
available. To carry out the test an external standard gauge shall be connected in parallel to the Density monitor and the reading in the reference gauge & standard gauge shall be
compared through out the range. In particular the pressure readings for the alarm thresholds shall be verified. As the standard gauge is normally not temperature compensated the reading shall be corrected for the ambient conditions.
ACCEPTANCE CRITERIA:
Criteria is Po = Pd +- 0.2barg
Where,
Po = Operating pressure
Pd = Designed operating pressure
NAME OF THE TEST:
SF6 ALARM CHECKS
OBJECTIVE OF THE TEST
Gas Insulated Switchgear (GIS) consists of several bays and each bay contains different gas compartments separated by gas tight barriers. Gas barriers are indicated by yellow colour paint.
Manufacturer of GIS have specified the recommended value of pressure in their individual gas compartments/zones. The objective of the test is to check that the density monitor contacts are switching in relation to the variation of gas pressure/density in the respective gas compartment, according to the scheme provided.
STANDARD/SPECIFICATION REFERENCE OF THE TEST
For the CB compartments, a lockout feature shall be provided to prevent operation whenever SF6 gas pressure is less than that permitted by the design for satisfactory operation.
Two sets of voltage free electrical changeover contacts will be provided for every alarm for remote SCADA and repeat alarm facilities in addition to alarm facials incorporated in the LCC/marshalling kiosk associated with each primary circuit. Contact multiplying relays may be used.
In some type of switchgears if different pressures are maintained in CB & other compartments,
then high pressure (pressure rising) alarm shall be provided in the adjacent gas compartments.
PROCEDURE OF THE TEST
Ensure that control cable wirings are completed from the respective density monitors to the LCC Panel. Verify that control cable terminations are properly done at both ends. Check that proper labels and ferrules are provided at both ends as per the schematic drawing. Density monitor contacts switching can be verified either by varying the gas pressure in the gas compartment by
using gas handling machine or by a separate portable gas cylinder arrangement if non-return valve assembly is provided in the density monitor block. These alarms need to be verified with the approved schematic drawing of the LCC Panel.
ACCEPTANCE CRITERIA
Normally density monitors are temperature compensated. Permissible limit of variation in the operation of density monitor contacts willl be specified by the manufacturer of density monitor.
NAME OF TEST:
DS & ES manual operation
OBJECTIVE OF THE TEST:
To ensure proper close/open operation of CB DS ES.
STANDARD/SPECIFICATION REFERENCE OF THE TEST: 62271-102
PROCEDURE OF TEST:
Each device in the 132kV GIS shall be operated manually to ensure the perfect operation of the device along with the interlocks for mechanical operation. Depending on the manufacturer there will be different types of interlocks for mechanical operation for the safety of operating personnel.
These interlocks have to be verified during the operation. Mechanical position indication of status& semaphore indications shall also be checked during this test. Operating handles are usually used for the mechanical operation of devices. Identification of operating instructions, warnings if any during mechanical operation etc shall be checked.
ACCEPTANCE CRITERIA:
Operation shall be smooth & there should not be any abnormal sound from operating mechanism.
Mechanical indication shall also be aligned.
NAME OF TEST:
CB local electrical and manual operation
OBJECTIVE OF THE TEST:
To ensure proper close/open operation of CB
STANDARD/SPECIFICATION REFERENCE OF THE TEST: 62271-100
PROCEDURE OF TEST:
The CB close /Open operation shall be performed first at rated control voltage. After giving close/open command from LCC the CB wwill be checked whether it is closed/opened properly or not. If there is a glass window the physical status of the CB contacts shall be verified. Semaphore and electrical indication for close/open of CB also we have to verify at LCC. Mechanical indication on the CB poles shall also be verified.
Manual Charging of Closing spring & operation of CB A discharged spring shall be manually charged using the manual spring charging handle.
After charging the closing spring CB can be closed/opened by mechanical operation push button. Semaphore and mechanical indication of close/open shall be verified. CB counter operation& spring status indication shall also be verified.
ACCEPTANCE CRITERIA:
Operation should be smooth & mechanical indications must be accurate.
NAME OF TEST:
CB Timing Measurement
OBJECTIVE OF THE TEST:
To measure the closing and opening time of main contact of Circuit Breaker (R, Y & B phases) & including the discrepancy among the poles operation timing.
STANDARD/SPECIFICATION REFERENCE OF THE TEST: 62271-100.
PROCEDURE OF TEST:
In each CB there are two nos. of closing coils and two nos. of tripping coils. Timing
measurement has to be done for all these coils.
At first, simulate all the field point of CB (After removing CB control plug) by using a
simulator. Usually a PROGRAMMA kit or any other suitable instrument can be used for
measuring close/open timing of Circuit Breaker. At rated voltage we have to give the
close/open pulse from that kit. The duration of operation will be recorded in the instrument & it shall be displayed in the form of graph.Following shall be recorded for open, Close & OCO operation
Duration of operation of individual poles & discrepancy in operation of poles
Close Coil/ Trip coil current.
One set of NO & NC contact operation timing.
Time for CB close /open (individual R, Y & B) can be measured from the graph. Closing and opening current also we can take along with that graph. Pole discrepancy also we have to check for close/open time. 1 NO & 1 NC auxiliary contact timing also we can take along with that graph.
ACCEPTANCE CRITERIA
Acceptance criteria shall be obtained from the respective manufacturer.
For eg: AREVA 132 kv GIS B165:
Closing time: 100 to 115 ms Pole discrepancy:
5 ms (¼ Cycle)
Opening time: 27 to 31 ms Pole discrepancy:
3.33 ms (1/6 Cycle)
NAME OF TEST:
CB FUNCTIONAL TEST
OBJECTIVE OF THE TEST:
To verify the function of circuit breaker as a whole. For verification of the CB function the following tests/ measurements are employs.
CB Operation.
Verification of 2Co or OCO operation
Verification of nameplate.
Lock out function.
CB spring charging time & motor current measurement.
Function of anti condensation Heater & its current measurement.
Checking of anti pumping feature.
PNT function in case of Single pole mechanism
Operation of CB counters.
STANDARD/SPECIFICATION REFERENCE OF THE TEST: 62271-100
PROCEDURE OF TEST:
CB operation shall be performed through all the closing &opening coils. Care must be taken to see that the second close coil are included in the circuit as it is normally kept as spare. OCO operation/ 2CO operation (Depending on the type of Mechanism) shall be verified. OCO /2CO operation are performed after switching off the spring charging motor/ Hydraulic Motor supply MCB after closing the CB. MCB shall be
switched ON only after performing the entire operation
Pole not together is applicable in case of single pole mechanism breakers. In case
such cases PNT function shall be verified.
Antipumping: Prohibits the closing command to CB incase of repeated closing
command.
The close command shall be given continuously by keeping the TNC switch in close position. Because of the continuous close command the antipumping relay will be
picked up and closing circuit will be electrically isolated. Then give a trip command through emergency push button. Though closing command is persisting, CB should not be closed without de-energizing the antipumping relay.
CB lock out function for SF6 pressure drop/ Spring Discharge/ hydraulic pressure
drop etc shall be checked for close lock out, Trip lock out & General Lock out.
Measurement of spring charging motor current shall be measured during the
operation of the spring charging motor by using an appropriate clamp meter. Usually
the spring charging motor will be DC motor. Spring charging time shall also be
measured by using a stopwatch.
Function of anti condensation heater shall be performed by adjusting the thermostat
in the control circuit. Heater current shall be measured during this time using an
appropriate clamp meter.
CB operational counter verification shall be done during the operation of CB. Care
must be taken to ensure that the counter is increasing once for a close & open
operation. A non-resettable type counter is preferred as CB counter.
ACCEPTANCE CRITERIA:
All the above functions should be perfect.
NAME OF TEST:
GIS Contact Resistance Measurement of the Main Circuit.
OBJECTIVE OF THE TEST:
The purpose of the test is to verify that the main circuit resistance of the GIS is within the factory data. The test shall be carried out for the entire primary connections of the
switchgear including earth switches.
STANDARD/SPECIFICATION REFERENCE OF THE TEST: IEC 62271-203
PROCEDURE OF TEST:
The resistance of the main circuit shall be measured by injecting 100A DC current. The connection is to be done as per fig.-1. Voltage probes shall be connected inside the current probes. Care has to be taken to avoid current injection & voltage measurement from the same point as such measurement can cause errors.
ACCEPTANCE CRITERIA:
The measured value of resistance shall be +/- 20 %(µΩ) of the factory data.
NAME OF THE TEST:
SF6 GAS PERIODICAL CHECK FOR LEAKAGE
OBJECTIVE OF THE TEST
The objective of the test is to check that there is no SF6 leakage from the GIS and the condition of the gas barriers and gaskets/o-rings are perfect.
STANDARD/SPECIFICATION REFERENCE OF THE TEST
The Manufacturer should be prepared to guarantee the equipment for a gas loss of not more than 0.5% per annum in any single gas compartment.
PROCEDURE OF THE TEST:
SF6 gas leakage is to be checked by gas leak detector for assembled section covered with plastic at site after more than 24 hours accumulation.
ACCEPTANCE CRITERIA:
The amount of gas loss shall be not more than 0.5% per annum in any single compartment.
NAME OF TEST:
HVAC Test of 132kV GIS
SCOPE OF TEST:
The high voltage power frequency withstand test on 132kV gas insulated switchgear to check the dielectric integrity of the switchgear
OBJECTIVE OF THE TEST:
It is important for GIS to check the dielectric integrity in order to eliminate fortuitous causes (wrong fastening, damage during handling, transportation, storage and installation, presence of foreign bodies, etc.) which might in the future give rise to an internal fault.
The aim of the HVAC test is to check the dielectric integrity of the completed
installation and of detecting irregularities as mentioned above. Normally the dielectric test shall be made after the GIS has been fully installed and gas-filled at the rated filling density preferably at the end of all site tests, when newly installed.
STANDARD/SPECIFICATION REFERENCE OF
THE TEST:
Dielectric test will be performed in accordance with clause 3.02 of section 16359 of the specification and clause 7.107.1.5 procedure A of IEC 60517.
IEC 60298[8] and IEC 60517[9] are applicable for dielectric test on the main circuit
of the GIS.
PROCEDURE OF TEST:
The test will be made on the entire assembled GIS. The test voltage will be applied between main circuit and grounded enclosure keeping the other two phases shorted and earthed. The insulation resistance between main circuit and ground will be measured before and after AC high voltage test by using 5000V megger for 1 minute. The IR value shall be more than 2000 M-Ohm. CT secondaries shall be isolated from the relays, shorted and grounded at LCC. The GIS earthing system is
to be checked for proper connection to main earth grid.
Voltage Application:
Test voltage : 80% of factory tested voltage
- Duration : 1 minute
- Frequency : 50Hz (Application of variable frequency is under consideration)
- Gas pressure : Rated gas density
- The test voltage will be applied between each conductor and the earthed enclosure; other two phases will be earthed.
- Voltage transformer will be excluded under the AC high voltage.
- The test voltage will be applied through the temporary test bushing fitted at the
busbar/Cable side of the GIS.
- VT ratio check will be performed during the AC high voltage test at Rms Voltage
- Voltage rising will be performed as per the following pattern.
The following shall be completed before HV test GIS erection shall be completed in all respect.
Contact Resistance measurement of the entire primary circuit shall be completed All devices must be operated at least five times either electrically/mechanically.
Earthing of GIS, Safety aspects shall be ensured.
ACCEPTANCE CRITERIA:
The GIS shall withstand HVAC voltage for 1 minute, while the partial discharges
recorded during HV test at specified voltage shall be less than 10pC.
NAME OF TEST:
132kV GIS PD Coupler Sensitivity Check.
OBJECTIVE OF THE TEST:
To confirm that the sensitivity of each PD sensor is enough to pick up 5pC or less of
PD at any point in the GIS.
STANDARD/SPECIFICATION REFERENCE OF THE TEST:
IEC Standards: As per IEC 62271-203 ; CIGRE guide lines.
PROCEDURE OF TEST:
PD couplers (UHF Sensors) are mounted at different places on GIS. PD shall be
measured during HV test of the GIS. Each coupler shall have enough sensitivity to
pick up 5pC or less of PD at any point in the GIS. So before high voltage test & PD
measurement, sensitivity of PD sensor is to be verified.
The sensitivity of each UHF coupler is confirmed by the following method.
1) Inject artificial PD (rectangular pulses with rise time less than 1ns) with voltage
of 20V from one UHF coupler. This level is assigned as (a). The specification of
the artificial pulse according to CIGRE TF 15/33.03.05 is as follows:
- Rise time: less than 1 nano second.
- Magnitude of impulse voltage: N/A (it is dependent on the sensor for injection and/or injection value).
- Pulse with: more than 500 nano seconds( rectangular pulse)
- Time between consecutive pulses: less than 100kV (e.g. 50/60Hz).
2) Measure PD signal from another UHF coupler. This level is assigned as (b).
3) Attenuation between UHF coupler (a) and (b) is calculated and this is assigned as (c) = (a) + (b)
4) Take one half of attenuation (simulate PD source at the middle between two UHF
couplers) and this is assigned as (c´) = (c)/2
5) The minimum sensitivity assigned as (d), is calculated by the following formula.
d = 300X10((-85+25+ c´)/20)
Where, +25 is the gain of the amplifier
6) The test result and calculated result is to be shown in a table.
The test circuit of attenuation measurement is shown bellow,
ACCEPTANCE CRITERIA:
Each PD sensor shall have enough sensitivity to pick up 5pC or less partial discharge at any point of the GIS.
NAME OF THE TEST:
VOLTAGE SELECTION SCHEME & SYNCHRO CLOSE CHECKS
OBJECTIVE OF THE TEST
Switchgear consists of double busbar arrangement. A separate LV scheme ( voltage Selection scheme) is utilized for making proper selection of busbar voltage by making use of line VTs secondary. Selection of a particular line voltage as the respective busbar voltage is accomplished in accordance with the connection of busbar disconnector& CB to the respective busbar.
Interposing VTs with 1:1 ratio also inserted in VT secondary circuit for electrical isolation of VT secondary. The scheme is designed to get proper selection of busbar voltage depending upon the switching to the different busbars.
The objective of the test is to check that proper selection of voltage is made in accordance with the switching to the respective busbar.
PROCEDURE OF THE TEST
Ensure that control cable wirings and interpanel buswirings are completed as per the approved scheme in the LCC Panel. Verify that terminations are properly done and ferrules are provided at both ends as per the schematic drawing. R & Y phases of the VT secondary is used for synchro selection scheme. Energized condition can be simulated by injecting variable AC voltage in the VT secondary circuit. Before voltage injection ensure that VTs primary disconnectors and secondary isolating links are open to avoid back charging of the VT.
Voltmeters shall be connected in the bus
coupler panel at the corresponding points to measure busbar I, II, V & VI, running and incoming voltages in relation to the various switching combinations of the power circuit. Check that proper voltage is extending to the running and incoming voltage buses by actuating synchro-selecting relay. Check that any voltage induced in the non-energized buses. Verify that what means provided to reduce the level of induced voltage in the non-energized buses.
Check the synchro closing condition by varying incoming and running voltage parameters.
Synchronization command will be issued by the synchrocheck relay only when both the incoming& running voltages are within the specified limits as mentioned below. Create the negative conditions to check the synchronizing scheme and software program are functioning correctly.
ACCEPTANCE CRITERIA
Parameters for synchro closing
Difference in voltage : ±10%
Difference in frequency : ±0.5 Hz
Difference in phase angle : ±10 degree
NAME OF THE TEST:
Operational Interlocks. (LOCAL & REMOTE)
Objective of Test: -
To avoid the human mistakes during the operation of the equipments and devices in
the substations. The interlock will be advisory system to support the operators and the site engineers with special expert information and knowledge to guaranty safe operations of the equipments.
The interlock system is not a fixed scheme; it is changed from manufacturer to manufacturer and depending on operational safety.
There are different control level of the equipments in side the substations and each
level having different inter lock, the control can be as follow:
Mechanical operation ,Local electrical operation, Remote & SCADA operation
Based on the above we can segregate the interlock test as follows:
1. Mechanical interlock test
2. Electromechanical interlock test
3. Local electrical interlocks
4. Remote interlocks.
Note: Prior to any interlock test all electrical &mechanical operation shall be completed. The interlock test shall be carried out as per the interlock logic sheet .
