A.Isolator is an device which is is used to isolate the circuit after opening the breaker. In order to maintenance purpose of breaker we will use isolator. In isolator we dont have any arc quenching medium so we cannot eliminate the arc in isolator. So after opening the breaker only we should open the isolator, so we should design some interlocks like below...
breaker close condition isolator should not open.
breaker open condition isolator can close or open.
different types of isolators which are using at field...
1. Double break type.
2. Knee type.
3. Single break type.
Q.What is the Earth switch and what is the role of earth switch in substation?
A. Earth switch is very important equipment as per safety of humans. While taking should down of any Equipment first we have to discharge the charge stored in it before doing any work on that. So in order to discharge the charge we have to connect earth switch (out door substation) or cable earthing trolley (in door substation. We have to put the earth switch in close position because of there, voltage will induce in dead equipment due to line running beside it.
different types of isolators which are using at field...
1. Double break type.
2. Knee type.
3. Single break type.
Q.What is the Earth switch and what is the role of earth switch in substation?
A. Earth switch is very important equipment as per safety of humans. While taking should down of any Equipment first we have to discharge the charge stored in it before doing any work on that. So in order to discharge the charge we have to connect earth switch (out door substation) or cable earthing trolley (in door substation. We have to put the earth switch in close position because of there, voltage will induce in dead equipment due to line running beside it.
DIFFERENT TESTS:
1. INSULATION RESISTANCE TEST FOR ISOLATOR MOTOR WINDING....
Remove all connections to motor and apply 500v by megger.
2. OPERATE THE ISOLATOR MOTOR AND MEASURE THE MOTOR CURRENT...
Measure the motor current by using AC leakage tester.
3.MEASURE THE OPERATING TIME (OPENING TIME,CLOSING TIME)...
Measure the opening and closing time using stop watch.
4.OPERATING TIME OF AUXILIARY CONTACTS...
Auxiliary contacts will change their status ( like NC to NO,NO to NC). Measure the time taken using stop watch
5. INSULATION RESISTANCE TEST...
Measure the insulation resistance of insulators of isolator.
6. COIL PICK UP and DROP VOLTAGE...
6. COIL PICK UP and DROP VOLTAGE...
Increase the DC voltage from zero and apply across the coil (ex. closing coil) by using 1ph variac and DC power pack. Record the voltage where the coil pick up. Now decrease the voltage from that position and note down the voltage at where the coil will reset.
note: Generally pick up voltage is greater than drop voltage ,because of magnetic retentivity.
7.CONTACT RESISTANCE MEASUREMENT...
It is the important test in order to check the goodness of contact made by the isolator. It will be done by using CRM kit by injecting 100 amp DC current. Never do this test when isolator is in open condition.
The following are the images at field....
It is the important test in order to check the goodness of contact made by the isolator. It will be done by using CRM kit by injecting 100 amp DC current. Never do this test when isolator is in open condition.
The following are the images at field....
DBR type isolator for 400kv at RANCHI (india)
KNEE type isolator in closed position in India (765kv)
operation of isolator when charging dead line
knee type isolator when in open condition
Thanks for sharing this valuable information. You have posted a trust worthy blog keep sharing. Nice article i was really impressed by seeing this article, it was very interesting and it is very useful for me. CONTACT RESISTANCE TESTER
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ReplyDeleteGreat information. Thanks
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