A. List of Tests to be carried out in MV Cable
a. Phase Identification Test.
b. Insulation Resistance Test (Before and after HV Test)
c. Sheath Integrity Test.
d. Conductor HV Test
PHASE IDENTIFICATION TESTING
1 Purpose:
To ensure the continuity and phasing of the cable from terminal to terminal, the cable sheath shall be tested using a minimum of 250V DC. The phase checking test shall be done after the complete termination works.
2 Test Equipment Used:
Discharge Rod
Connection leads
Digital Multimeter
Warning tape, Caution Board etc
Tools
3. Pre – Requisites:
All pre-requisite mentioned in page 1 shall be ensured.
Ensure the completion of cable installation and Termination
Ensure labelling with Phase Identification is provided.
Ensure that none of the cable terminations are touching each other.
4. Test Procedure Details:
Ensure labelling with Phase Identification is Provided.
Check the continuity with multimeter for individual cables.
The correct phasing shall give low resistence approx. 0.3Ω (Shorted condition).
Verify the proper phase markings at test location & remote end.
Above procedure shall be repeated for the other phases also.
The test results shall be recorded in test format.
Insulation Resistance Test
1 Purpose:
To check any damage occurred during cable pulling, To check the insulation integrity before and after any voltage injection. To ensure conductive parts are isolated from ground.
2 Test Equipment Used:
Discharge Rod
Connection leads
Insulation Resistance Tester
Digital Multimeter
Warning tape, Caution Board etc
Tools
3. Test Procedure Details:
All power cables are in final position (Trefoil) with Cable tie fastened.
Ensure that no other party is working near to testing area.
Connect negative terminal of the Insulation test kit to the conductors of same phase together ( all will be shorted together) and positive to earth. The other two phases shall be earthed.
Before injection make sure that far end is open and isolated from earth.
Apply 1 KV DC for one minute and measure the Insulation Value.
Connect the discharge rod to the cable after switching off the kit
The test results shall be recorded in test format.
Same test procedure shall be done for other phase as well.
This test will be done before and after the HV test of cable to ensure the healthiness of the cable.
DIAGRAM FOR INSULATION RESISTENCE MEASURMENT TESTING
Purpose :
To determine the healthiness of the sheath of the cable after completion of cable
installation work
Equipment used for the test:
DC high voltage kit.
Temperature & Humidity indicator.
Discharge / Earth Rod.
Connection leads.
Hand Tools.
Warning tape & Caution Board.
Test Procedure Details:
Sheath test to be carried out after completion of back filling work.
Earthing connection of the cable will be isolated, to segregate the cable from
earth.
Connect testing set to the cable as per connection diagram.
All safety points to be checked before switching on the power supply to the testing set and communicates with remote end.
Raise voltage to 10 kv gradually and observe leakage current on Ammeter, Hold it for 60 sec. And record leakage current on the test format.
Switch off the power supply of Testing set and wait till the voltage reaches to zero.
Discharge the cable using by discharge rod. Connect the next phase as per the above and repeat the process.
DIAGRAM FOR SHEATH TEST
DC HIGH VOLTAGE TEST.
Purpose :
To determine the healthiness of the cable insulation after completion of cable installation work and before energisation.
Equipment used for the test:
DC high voltage kit.
Discharge / Earth Rod.
Connection leads.
Hand Tools.
Warning tape & Caution Board.
Procedure Details:
Test shall be carried out after completion of cable installation and back filling work,
All Electrical tests to be completed before HVDC test,
11KV Cable connections to the Switchgear and Transformer shall be disconnected
Ensure good grounding connection,
Measure IR value of the cable before HV Test and record the readings
Connect testing set to the cable as per connection diagram.
All safety points to be checked before switching on the power supply to the test set and communicates with remote end.
Raise voltage to 25.4 kv gradually and observe leakage current on Ammeter.
Hold it for 15 Minutes. And record leakage current on the test format.
Switch off the power supply of Testing set and wait till the voltage reaches to zero.
Discharge the cable using by discharge rod.
Connect the next phase as per the above and repeat the process.
DIAGRAM FOR HV DC TEST
HV CABLES
Sheath Integrity Test before Cable laying (Drum test)
Purpose of the test:
To ensure that the cables are free from defect& fault during transportation from factory to site andto avoid any ambiguity between manufacturer & cable contractor.
Equipment used for the test:
DC high voltage kit.
Discharge / Earth Rod.
Connection leads.
Hand Tools.
Warning tape & Caution Board.
Safety Requirements:
1.All safety measures should be checked & confirmed by safety officer.
2.Barricade the cable drum and provide
warning tapes.
3.All the power tools and hand tools to be properly insulated.
4.Unwanted materials to be r removed from the work location.
Test Procedure:
1.Cable drum shall be placed in a leveled
ground and suitable stoppers shall be placed
on both sides toprevent the movement of the
drum .
2.Cable drum to be kept open and both ends of the cable to be taken out.
3.Removal of graphite coating of outer protection sheath at both ends (<20 cm)
4.Nail to be inserted up to lead sheath at test
end Graphite removed area.
5.Earthing to be provided to graphite coating
area and the cab le drum itself,
6.Inject voltage gradually up to 10KV, kept injection for 60 sec and note the leakage current.
7.Switch off the power supply of the test kit
and allow self discharge.
8. Discharge the cable by discharge rod.
9.Repeat the test for other cable drums.
All test results are recorded in test format.
Purpose of the test:
•To check any damage occurred during cable
pulling.
•To check the insulation integrity before and
after any voltage injection.
•To ensure conductive parts are isolated from
ground.
Equipment used for the test:
• Insulation Tester (Megger).
• Temperature & Humidity indicator.
• Discharge / Earth Rod.
• Connection leads.
• Hand Tools.
• Warning tape & Caution Board.
Safety Requirements:
•All safety measures should be checked &
confirmed by safety officer.
•Barricade the cable drum and provide warning tapes.
•All the power tools and hand tools to be
properly insulated.
•Unwanted materials to be r removed from the work location.
Test Procedure:
1.All power cables are in final position (Trefoil) with Cable tie fastened
2.Ensure that no other party is working near to our testing area.
3.Connect negative terminal of the test kit to
the test terminal & the positive to earth.
4.Before injection to ensure the far end is open and isolated from earth.
5.Switch on the instrument, apply 1 KV DC for one minute and note the Insulation Value.
6.Switch off the power supply and wait till the
residual voltage gets self discharged.
7.Discharge the cable with earth rod.
8.Repeat the process for all the other phases.
All test results are recorded in test format.
Acceptance criteria:
Insulation resistance of XLPE shall be measured at 1 kV‐‐DC for 1 minute and the measured value shall not be less than 100 MΩ per 1000m at ambient temperature. The actual resistance values can be higher or lower, depending upon factors like temperature or moisture content of the insulation (resistance decreases in temperature or moisture).
Test Diagram
test
Purpose of the test:
•To make sure the correct phasing of the cable before termination and also prior to dockin.
•To determine the healthiness of the sheath of
the cable after laying & before HVAC test.
Equipment used for the test:
• DC high voltage kit.
• 1kV Insulation Tester.
• Temperature & Humidity indicator.
• Discharge / Earth Rod.
• Connection leads.
• Hand Tools.
• Warning tape & Caution Board.
Safety Requirements:
•All safety measures should be checked
& confirmed by safety officer.
•Barricade the cable drum and provide warning tapes.
•All the power tools and hand tools to be
properly insulated.
•Unwanted materials to be r removed from the work location.
Test Procedure:
•Ensure that no other party is working near to
testing area and in the other end of the cable
a) Sectional Phasing
1. Checking of the safety measures for both
ends.
2. Each phase shall be tested one by one.
3. Connect negative terminal of the test kit to
the conductor & the positive to earth, connect
the other end ofthe cable to earth by keeping
other two phases in open at far end.
4. Injection voltage to be limited to 50 -150V in normal situations.
5. Switch on the IR Tester apply the voltage, now successively ground each phase cable from
the far end.
6. The correct phase shall indicate 0ΩΩ (Short condition) while shorted in the far end with all
other phase open.
7. This can be further cross checked by removing and connecting the ground of the phase at
far end, now themeter shall read open and 0Ω respectively as per the connection at far end.
8. Provide proper phase markings at test
location & remote end.
9. Above procedure shall be repeated for checking the other phases.
10. The test results are recorded in test format.
b) Sectional Sheath test
1.Removal of graphite coating of outer protection sheath a t both ends (15‐20 cm )
2.Nail to be inserted up to lead sheath at test
end Graphite removed area.
3.Insulation resistance test (1kV) to be
performed for all cables.
4.Inject voltage gradually up to 5KV, for 60 sec and note the leakage current.
5.Switch off the power supply of the test kit
and allow self discharge.
6.Discharge thee cable by discharge rod.
7.Repeat the test same for other cables.
8.Repeat Insulation resistance test (1 kV) for all cables.
9.All test results are to be recorded in test
format.
Acceptance criteria:
Sectional Phasing
Ensuring the tested phase is in short condition while other phases are in open condition,the test to be considered as
passed
Sectional Sheath Test
5kV DC voltage should withstand for a time period of 1 min without any breakdown.
Purpose of test:
To ascertain the withstanding capacity and proper functioning of SVL.
Equipment used for the test:
• DC high voltage kit.
• 1kV Insulation Tester.
• Temperature & Humidity indicator.
• Discharge / Earth Rod.
• Connection leads.
• Hand Tools.
• Warning tape & Caution Board.
Safety Requirements:
•All safety measures should be checked & confirmed by safety officer.
•Barricade the cable drum and provide warning tapes.
•All the power tools and hand tools to be
properly insulated.
•Unwanted materials to be r removed from the work location.
Test Procedure:
1.Ensure that the link box installation
completed & connections made properly.
2.Disconnect all the SVL leads from the
bonding links.
3.Clean it properly & handle the housing part
carefully.
4.Ensure there is no physical damage in the
SVL.
5.Confirm the rating of the SVL
6.Insulation resistance test (1 kV) to be performed for all SVLs.
7.One end of the SVL to be connected as injecting point from the HVDC test kit and other end
to ground.
8.Switch on the HVVDC test kit.
9.Record the Leakage current at UC ‐2, UC ‐1, and UC , while Voltage is gradually applied across two points.
10.Increase voltage until the cut off voltage reaches at 100 µA & 1 mA.
11.Switch OFF the test Kit
12.Discharge the SVL until the voltage comes
down to zero.
13.Perform Insulation Resistance test (1KV) on SVL Repeat the above tests for all other SVL’s
Acceptancee Criteria:
SVL shall be in open condition when applying voltage up to Uc voltage.
SVL to regain its open condition after achieving the above
mentioned leakage currents.
Test Diagram
Link box Contact Resistance Test
Purpose of test:
To make sure that the links are tightened
properly inside the link box
Link box Contact Resistance Test
Purpose of test:
To make sure that the links are tightened
properly inside the link box
Equipment used for the Test:
• Micro Ohm Meter).
• Connection leads.
• Warning tape & Caution Board.
Safety Requirements:
•All safety measures should be checked &
confirmed by safety officer.
• Barricade the test area with warning tapes.
Test Procedure:
1.Ensure the Completion of all Link box
installation
2.Fix the Links & SVL as per approved the
schematic diagram.
3.Make required tightness of all links in the Link Box.
4.Coordination with other working team to
ensure no other test on it.
5.After setting the instruments connection as
per the below test diagram, the contact
resistance shall be measured..
6.If the links are not fixed properly, the measurement shall be high due to the potential drop
between the gaps of two contacts.
7.The test results are recorded in test format.
Acceptance Criteria:
The measured value should be less than 20 µ ΩΩ.
Test Diagram
132KV Cable Phase verification through
Sheath
Purpose of test:
To make sure the sheath Bonding System is installed correctly.
Equipment used for the test:
• IR Tester (MEGG ER)
• Discharge Rod
• Connection leads
• Tools
• Warning tape, Caution Board etc.
Safety Requirements:
•All safety measures should be checked
& confirmed by safety officer.
•Barricade the cable drum and provide warning tapes.
•All the power tools and hand tools to be
properly insulated.
•Unwanted materials to be r removed from the work location.
Test Procedure:
1.Ensure the completion of cable installation
and back filling off cable route.
2.Ensure all Bonding cables
(Inner & Outer core) Labeling completed.
3.Ensure NO other parties working near to thee testing area.
4.Both solid earthing links shall be isolated
from the earth.
5.SSVL connections to be isolated in the link
box and bonding connections to be
maintained as per bonding scheme.
6.Sufficient manpower to be placed at both
ends of testing &each phase shall be tested
one by one.
7.Connect negative terminal of the test kit to
the conductor & the positive to earth,
connect the other end of the cable to earth by keeping other two phases in open at far end.
8. Injection voltage to be limited to 50‐150V in normal situations.
9.Switch on the IR Tester apply the voltage,
now successively ground each phase cable
from the far end.
10.The correct phase shall indicate 0ΩΩ (Short condition) while shorted in the far end with all
other phase open.
11.This can be further cross checked by removing and connecting the ground of the phase at
far end, now the meter shall read open and 0Ω respectively as per the connection at far end
12. Provide proper phase markings at test location & remote end.
13. Above procedure shall be repeated for checking the other phases.
14. The test results are recorded in test format.
Acceptance criteria:
Sectional Phasing
Ensuring the tested phase is in short condition while other phases are in open condition, the test to be considered as passed
CABLE CONDUCTOR RESISTANCE TEST
Purpose:
Conductor Resistance values for the cable are measured as part of pre commissioning
tests in order to ensure the integrity of the joints and termination.
Equipment used for the Test:
• Micro Ohm Meter.
• Connection leads.
• Warning tape & Caution Board.
Safety Requirements:
• All safety measures should be checked & confirmed by safety officer.
• Barricade the test area with warning tapes.
Test Procedure:
Connecting lead wire will be used for connecting the conductors at far end of the cable.
DC Resistance of the connecting lead will be measured.
Two cable cores will be connected to each other at far end of the cable, (Phase R & Y).
At other end connect the Michro Ohm meter in Phase R & Y.
The DC resistance of these two cables also will be measured.
Connect the meter to Phase Y & B and shift the connecting leads at far end to
Phase Y&B as well
Measure the DC resistance
Repeat the same test by connecting between Phase R &B as well
Conductor resistance is calculated by the below formula.
Rt = Rm – RcL
Where Rt = Measured Resistance, RcL = Shorting Lead Resistance, Rf = Final
Resistance
Measured Resistance shall be converted to 200 C , By using formula
R20 =Rt/L (1+0.00393(T-20)
Where R20 is calculated Resistance at 200C t is measured temperature,(for 630sq mm copper conductor , Coefficient of resistivity is 0.00393).
Acceptance criteria:
The measured resistance value corrected at 20 C must be equal or less than the design
resistance of 630mm2 cable (0.0283 ohm/km)
HVAC Test on CABLE and Terminations
Purpose
The purpose of the test is to ensure that the cable and terminations are fit for service and
safe to energize.
The method used will be to apply a sinusoidal voltage between each cable conductor and
insulation shield (ground) in turn for a period of time.
The cable has to withstand 132KV for 1 hour.
The AC voltage will be generated by LC series resonance whereby the cable under test will
be the capacitor and a high voltage reactor will be the inductor.
An exciter transformer connected between the low voltage terminal of the reactor and
ground will be used to energize the resonant LC pair. The exciter transformer is energized
from a variable frequency inverter via a isolation transformer. The Inverter output
frequency can be varied electronically between 20HZ and 300HZ.
Equipment / Accessories to be used for the
Test:
• Resonant frequency High Volt AC test kit
• 5kV insulation tester
• Discharge / Earthing rod
• Connection leads
• Hand Tools
• Warning tape & Caution Board
Safety Requirements:
•Safety officer shall be available & safety
persons to be kept a t all entrance/ exits.
•Safety measures to be checked by safety
officer.
•Take confirmation of site readiness from GIS cable box manufacturers’ at substation and coordinate with other contractors before
starting the test.
•Ensure no other party is working in the GGIS room and basement.
•The testing area to be completely barricaded.
•Provide warning tape on the area where the
circuit to be tested.
•Provide warning sign inside substation of circuit of be tested
•Keep sufficient s supervisor far end and
testing end during the test.
•Fire extinguisher (C02) shall be available at
site.
TEST PROCEDURE
Site survey will be conducted to determine the appropriate location to assemble the test
equipment and capacitor divider (preferably GIS off-loading platform area).
HV winding of the IDT will be earthed inside the HV cable boxes.
Prior to start of test to ensure that the Transformer HV cable side oil
treatment completed and cable box filled with oil tested in lab.
GIS side to ensure that CB (Q0) is in Open condition and earth switch (Q52) in closed.
Quality of the gas filled in the cable boxes to be tested and ensured for its purity.
The terminations remote from the testing location to be barricaded and warning
signs displayed to indicate testing is likely to be in progress.
During application of test voltage , access to the IDT / Basement room will be restricted
and a watchman will be stationed near IDT area terminations as a safety precautions.
The free-air electrical clearance of all grounded energized parts shall be minimum of 25mm per 10KV ( peak) of applied test voltage to avoid flashover.
AC resonant test set will be installed adjacent to the GIS into which the HV test adopters
have been installed. If a connection cannot be made between the HV test set and GIS HV
adopter in a single span an intermediate temporary support will be erected to support the HV test lead.
Copper wire 6sq.mm test lead will be contained within 100mm diameter aluminum foil ducting to reduce the corona losses and minimize the generation of external partial
discharges.
All test equipment grounds will be securely connected to substation ground system.
Diesel genset will be the source of LV input power for the test equipment.
Rigid safety barricades, warning signs and flashing warning lights will be erected around
the test site.
All cable shields and link boxes will be in their service position except for SVL which will be
shorted to avoid being damaged in the event of flash-over during testing.
HVAC test will commence with the measurement of cable insulation resistance between conductor and insulation shield one phase at time using 5KV meggar.
Measured values will be recorded at the completion of one minute of measurement.
Each conductor will be connected to ground on completion of IR test.
Ground will be disconnected from the termination of the first cable to be tested.
HV output terminal of the test lead will be connected to cable terminal via low corona test
lead.
Cable HVAC test can be conducted one phase at a time or all three phases together as
agreed by the client and depending on availability of test adopters.
All test reports should be available at site prior to start of HVAC test.
Following a final check of safety arrangements, equipment connections & grounds, and after safety clearance from safety officer, the LV power supply to test equipment can beswitched ON from the genset.
PD measurement to be done prior to HVAC test at U0 and 1.5 U0, HVAC test can
commence if the PD is clear.
After entering the required details, in the software for testing, the frequency inverter is
energized.
The test voltages, stages and voltage duration will be given and the software will search for the resonant frequency automatically.
After reaching the resonant frequency point the test voltages for required duration can be
started or increased in stages. The AC test voltage for 60 minutes with max phase-phase
voltage of the system applied between conductor and metallic sheath /screen, will be
132KV AC .
In the event that a failure of the cable / accessories occurs during the HVAC test, the effect will be that the Q factor of the resonant circuit will be considerably degraded and
consequently the test voltages will immediately fall to reduced value. Damage at the failure
location would be minimal.
Test eqpt will be immediately shut down and the location and cause of the failure can be
investigated.
At the end of the specified test duration, the reactor output will be decreased automatically
to minimum and the inverter will shutdown.
PD measurement is repeated again after the HVAC test at 1.5 U0 and at U0.
After completing HVAC test , the tested cable will be earthed .
Test adopters will be shifted to the next circuit and HVAC test to commence as per the
above procedures.
After completion of HVAC test of all cable circuits IR measurement procedure will be
repeated.
Test adopters dismantled, links fixed inside the GIS cable boxes, Gas filled and treatment
done, Gas quality checked.
Acceptance Criteria
The test can be deemed passed, if it withstands 132 kV AC voltage per phase (U0 X 1.732) for new cable, 106 kV AC voltage / phase (U0 X 1. 732 X 0.8) for old cable for a duration of 1 hour at a frequency range of 200‐300Hz without any breakdown during test
Determination of the healthiness of cable / Termination after installation ( before energisation )The presence of PD activity occurring in terminations and joints can be determined and measured.
PD activity occurring within voltage range close to operating voltage of the cable can be a
predictor of early joint/ termination failure.
Equipment / Accessories to be used for the
Test:
• Resonant frequency High Volt AC test kit
• PDM Kit
• Discharge / Earthing rod
• Connection leads
• Hand Tools
• Warning tape & Caution Board
Safety Requirements:
•Safety officer shall be available & safety persons to be kept a t all entrance/ exits.
•Safety measures to be checked by safety
officer.
•Take confirmation of site readiness from GIS cable box manufacturers’
at substation and coordinate with other contractors before starting the test.
•Ensure no other party is working in the GGIS
room and basement.
•The testing area to be completely barricaded.
•Provide warning tape on the area where the
circuit to be tested.
•Provide warning sign inside substation of
circuit of be tested
•Keep sufficient s supervisor far end and
testing end during the test.
•Fire extinguisher (C02) shall be available at
site.
TEST PROCEDURE
1. All requirements for HVAC test to be
completed .
2. Identify and confirm the cable ( Feeder and phase) to be tested
3. Mount the UHF coupler on the stress cone of the cable termination for the individual.
4. Lay the UHF cable and connect one end of UHF cable to the coupler as per drawing
attached.
5. Provide an external ground before switch on the portable kit.
6. Switch on PD equipment and Laptop and
confirm the system is working properly
7. Confirm the communication between
processor unit and laptop is intact.
8. Create substation folder per test and sub folder for the PD measurement voltage
9. Inform the HV test coordinator for the
readiness of PD measurement.
10. BG noise level sensitivity 76kV BHV, 106kV BHV, 106 AHV and 76 AHV to be performed .
12. Check the background noise level and
adjust the threshold level and add hardware
filter to achieve better signal to noise ratio.
13. The above exercise should not affect
sensitivity of the PD coupler .
14. Perform PD coupler sensitivity test by
injecting 20V with CAL 2B PD pulse injector.
15. Confirm the coupler sensitivity for the all
cable to be tested and record.
16. In case of any abnormality observed the PD can be measured at different
voltage level (below 106kV) to know the injection on extinction voltage
level for PD activity.
17. Procedure 8 to 15 shall be repeated for other phase / Group cables.
18. The test report to be recorded in test
format.
Acceptance criteria:
During testing at 76kV & 114 kV no PPD
shall detected.
