Q. What is the need of doing timing test?
A. When fault occurs then it should be isolated as fast as possible in order to isolate fault.When we give the close command to breaker then it should be capable to make its contacts as good as in order to serve.
PROCEDURE...
1. Connect the feed back cables to poles of breaker ( R,R',Y,Y',B,B').
2. Connect the common negative wire to trip coil and close coil.
3 Connect positive wire trip coil and close coil separately.
4. Give the trip command by kit,and note down tripping time.
5. Give close command by kit , note down the closing time.
6. Give close open command by kit and note down close open time.
CONTACT RESISTANCE MEASUREMENT...
We have to find the contact resistance after closing the breaker in order to find the goodness of the contact.
PROCEDURE:
1. Connect the CRM kit to breaker after close operation.
2. Inject the DC current of 100Amp.
3. The kit will show the contant resistance in order of micro ohms.
PROCEDURE:
1. Connect the CRM kit to breaker after close operation.
2. Inject the DC current of 100Amp.
3. The kit will show the contant resistance in order of micro ohms.
INSULATION RESISTANCE TEST....
Insulation resistance test is to identify the healthiness of pole to ground and pole to pole insulation when breaker is in closed condition( R-N,Y-N,B-N,R-Y,Y-B,B-R), It is necessary to check the insulation when in open condition also (R-R',Y-Y',B-B').
PROCEDURE...
Insulation resistance
1/ Temperature.
1. Remove all external connections.
2. Apply DC voltage by using Megger.
3. Note down the readings given by Megger.
4. Discharge the voltage after completion of test.
5. Note down the temperature at the time of testing.
PROCEDURE...
Insulation resistance
1/ Temperature.1. Remove all external connections.
2. Apply DC voltage by using Megger.
3. Note down the readings given by Megger.
4. Discharge the voltage after completion of test.
5. Note down the temperature at the time of testing.
CIRCUIT BREAKER....
Q. What is circuit breaker ? What is the use in electrical system?
A. Circuit breaker is a device which will isolate the circuit under the fault condition in order to protect healthy part from faulty part by the command of Relay.It also used for switching operation under normal condition. So breaker is a device which can be operated at normal condition and abnormal conditions also.
When any fault occurs in electrical system it is necessary to isolate the fault part, other wise healthy part also effected by fault part. But while performing switching operation on circuit there is occurrence of arc for MV and HV voltages.
There are some points should keep in mind
1.Breaker can capable to open under fault condition.
2.Breaker can able to close when fault exist.
3.The Arc quenching medium should be capable to clear the arc other wise arc will re strike.
In order to find healthiness of breaker we have to do following test at field.
1.INSULATION RESISTANCE TEST...
2.CONTACT RESISTANCE MEASUREMENT...
3.TIMING TEST...
4.COIL RESISTANCE TEST...
Measure trip coil and close coil resistance by using multimeter.
5.INSULATION RESISTANCE TEST FOR MOTOR and COILS...
Measure insulation resistance for motor winding and trip coil and close coil separately by removing all external connections by applying 500volts dc.
A. Circuit breaker is a device which will isolate the circuit under the fault condition in order to protect healthy part from faulty part by the command of Relay.It also used for switching operation under normal condition. So breaker is a device which can be operated at normal condition and abnormal conditions also.
When any fault occurs in electrical system it is necessary to isolate the fault part, other wise healthy part also effected by fault part. But while performing switching operation on circuit there is occurrence of arc for MV and HV voltages.
There are some points should keep in mind
1.Breaker can capable to open under fault condition.
2.Breaker can able to close when fault exist.
3.The Arc quenching medium should be capable to clear the arc other wise arc will re strike.
SF6 Circuit breaker (400kv, India)
In order to find healthiness of breaker we have to do following test at field.
1.INSULATION RESISTANCE TEST...
2.CONTACT RESISTANCE MEASUREMENT...
3.TIMING TEST...
4.COIL RESISTANCE TEST...
Measure trip coil and close coil resistance by using multimeter.
5.INSULATION RESISTANCE TEST FOR MOTOR and COILS...
Measure insulation resistance for motor winding and trip coil and close coil separately by removing all external connections by applying 500volts dc.
SURGE ARRESTER...or LIGHTENING ARRESTER...
Q. What is surge arrester ? what is the use at substations?
A. When any feeder is coming there may be chance of occurring of surge voltage due to direct or indirect lightning or may be due to switching effects. So in order to save our equipment's connected to line from surge either we have to divert the surge to ground or absorb to decrease its effect. When the surge occurs surge arrester acts as short circuit and when surge is totally diverted then it acts as open circuit. The NON -LINEAR RESISTERS like METROSIL will be used in these devices.
Q. What is non linear resister?
A. Normal resister is which has liner characteristics for ohms law, means which will flow low currents for low voltages and high currents for high voltages. But nonlinear resister offers high resistance for low voltage and low resistance for high voltage.
Q. What is meant by SURGE?
A. A large amount of voltage is applied at very small time. Only small time has its effect on system.
The following are snaps of broken LA at field...
The metrosil plates which are arranged in stack
A. When any feeder is coming there may be chance of occurring of surge voltage due to direct or indirect lightning or may be due to switching effects. So in order to save our equipment's connected to line from surge either we have to divert the surge to ground or absorb to decrease its effect. When the surge occurs surge arrester acts as short circuit and when surge is totally diverted then it acts as open circuit. The NON -LINEAR RESISTERS like METROSIL will be used in these devices.
Q. What is non linear resister?
A. Normal resister is which has liner characteristics for ohms law, means which will flow low currents for low voltages and high currents for high voltages. But nonlinear resister offers high resistance for low voltage and low resistance for high voltage.
Q. What is meant by SURGE?
A. A large amount of voltage is applied at very small time. Only small time has its effect on system.
The following are snaps of broken LA at field...
name plate of LA at field
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