INTRODUCTION:
Routine tests should be carried out in accordance with IEC 60298 standards.
HV BREAKER :
CONTACT RESISTANCE TEST:
HV Breaker comprises three units such as Incomer,
Transformer and outgoing feeders. Each of these units must be subject to contact resistance prior to High Volt test.
The following procedures must follow for all three phases
Incomer to Ground
The above sequence carried out by making earth switch ON in Incomer breaker and then conduct the Contact resistance test by applying 100Amps to R phase to ground, Y phase to ground and B phase to ground.
The above sequence carried out by making earth switch ON in Outgoing breaker and then conduct the
Contact resistance test by applying 100Amps to R phase to ground, Y phase to ground and B phase to ground.
3. Transformer unit or Fuse unit to ground.
The above sequence carried out by making earth switch ON in Fuse unit breaker and then conduct the
Contact resistance test by applying 100Amps to R phase to ground, Y phase to ground and B phase to ground.
For the above sequence test, we need to ON the breaker of Transformer unit and Incomer unit. Regarding fuse unit we need dummy fuse to conduct the test. The dummy fuse
must be more than 100 Amps rating and without resistance. We should not use the rated Fuse provide by manufacturer. After arrange the zero resistance dummy fuses inside the transformer feeder (fuse unit) apply 100 Amps by contact resistance equipment between R phase of Fuse unit (transformer) to Incomer unit. Repeat the same for all other Y and B phases
5. Transformer unit (fuse unit) to outgoing unit
For the above sequence test, we need to ON the breaker of
Transformer unit and outgoing unit. Regarding fuse unit we need dummy fuse to conduct the test. The dummy fuse must be more than 100 Amps rating and without resistance. We should not use the rated Fuse provide by manufacturer. After arrange the zero resistance dummy fuses inside the transformer feeder (fuse unit) apply 100 Amps by contact resistance equipment between R phase of Fuse unit (transformer) to Incomer unit. Repeat the same for all other Y and B phases.
INSULATION RESISTANCE TEST:
Before injecting the voltage we must arrange safety precautions and ensure that the power cables must be removed from Breaker to transformer, the fuse must be removed from fuse unit. SF6 gas pressure must be positive.
The bushings of the breakers must be cleaned and tightened. All the breakers must be in ON condition.
Insulation Test before High Volt:
Measure Insulation resistance test between each phase to ground by applying 5KV DC through Megger for 1 Minute.
Before Apply 5 KV ensure that all the breakers of three units must be closed.
Insulation Test after High Volt:
Measure Insulation resistance test between each phase to ground by applying 5KV DC through Megger for 1 Minute.
Before Apply 5 KV ensure that all the breakers of three units must be closed.
High volt test:
Arrange Hivolt Equipment for injecting required voltage to ensure the system had the capability to withstand.
Before injecting the voltage we must arrange safety precautions and ensure that the power cables must be removed from Breaker to transformer, the fuse must be removed from fuse unit.
The bushings of the breakers must be cleaned and tightened. All the breakers must be in ON condition.
The following equation must be calculate for injecting the high volt
HV Test at
RatedVolta ge 2
3
The above High Volt must inject for 1 minute and it should withstand. Record the leakage current at the time of injection.
FUNCTIONAL CHECKS :
The following Mechanical interlocks must be tested
A- OPENING/ CLOSING SWITCH DISCONNECTORS
B- OPENING/ CLOSING TRANSFORMER TEE ON
C- OPENING/ CLOSING EARTH SWITCH OF
TRANSFORMER TEE
D- OPENING/ CLOSING FOR SWITCH
DISCONNECTORS
E- CIRCUIT BREAKER EARTH SWITCH INTERLOCK
Earth fault Indication test:
Apply rated CT current to the Earth leakage CT primary and observe the blinking of light at the leakage detector relay.
