CIRCUIT BREAKER TESTING
1. Visual Inspections.











Check nameplate information for correctness.
Check tightness of all bolted connections (torque wrench method).
Check all wiring is correct according to approved drawings terminal connections are secured.
Check quality of paintwork.
Check that all grounding cables are securely connected.
Check breakers, truck, rails, for proper alignment and smooth movement.
Check operation of all mechanical interlocks with associated disconnects, grounding switches,
racking truck mechanism, cubicle doors, etc.
Check for correct breaker position indication (breaker open/closed).
Check manual spring charge operation.
Verify correct spring status indication (spring charge d/discharged).
Verify that correct Dispatch Numbers have been installed.
2. Contact Resistance Measurements.





Close the CB.
The micro ohmmeter test is conducted with a current of 100 ADC.
Connect the test set to the first phase of the CB.
Record the reading.
Repeat it for all CB phases.
CB MAIN CONTACTS
MICRO OHM
METER
R
Y
CB CONTACT RESISTANCE TESTING ARRANGEMENT
B
3. High- Pot Test.
3.1 Insulation Resistance Test At 5kv DC.
At the CB Closed
 Connect the phases Y, B to ground and apply the test voltage between phase R and ground.
 Connect the phases B, R to ground and apply the test voltage between phase Y and ground.
 Connect the phases R, Y to ground and apply the test voltage between phase B and ground.
 Record the corresponding leakage current readings.
At the CB Open
 Connect the phases R, Y, B Cable side to the ground.
 Connect the phases R, Y, B Bus side to the test set.
 Record the corresponding leakage current readings.
3.2 High-Pot Test
 AC high- pot test shall be carried out in accordance with IEC standard at site. Normally it is
Three times of the phase to neutral voltage.
 The test will carry out for 60 second.
 If the test has been done at factory at any kV it will be done at site at 80% of the last time.
At the CB Closed




Connect the phases Y, B to ground and apply the test voltage between phase R and ground.
Connect the phases B, R to ground and apply the test voltage between phase Y and ground.
Connect the phases R, Y to ground and apply the test voltage between phase B and ground.
Record the corresponding leakage current readings.
CB MAIN CONTACTS
HIGH POT
TESTER
R
Y
B
AC WITHSTAND VOLTAGE TESTING ARRANGEMENT
At the CB Open
 Connect the phases R, Y, B Cable side to the ground.
 Connect the phases R, Y, B Bus side to the test set.
 Record the corresponding leakage current readings.
CB MAIN CONTACTS
HIGH POT
TESTER
R
Y
AC WITHSTAND VOLTAGE TESTING ARRANGEMENT
B
3.3 Insulation Resistance Test At 5kv DC.
At the CB Closed
 Connect the phases Y, B to ground and apply the test voltage between phase R and ground.
 Connect the phases B, R to ground and apply the test voltage between phase Y and ground.
 Connect the phases R, Y to ground and apply the test voltage between phase B and ground.
 Record the corresponding leakage current readings.
At the CB Open
 Connect the phases R, Y, B Cable side to the ground.
 Connect the phases R, Y, B Bus side to the test set.
 Record the corresponding leakage current readings.
4. Functional Check Of Trip Free And Anti Pump Circuits.






The Anti- Pump feature in the Breakers were tested as follows:
The Breaker was closed and the control switch was held in close position.
It was ensured that the breaker closes
The Breaker was tripped as below while the control switch was held in
Close position: A: Manually B: Electrically
It will be noted from the results that the Breaker does not attempt to re-close if a permanents
closing signal is applied.
5. Functional Checks Of Breaker Operation Counter.
6. Check Correct Operation Of All Auxiliary Contacts (For Breaker Open/Closed Positions).
7. Timing Test Using An Electronic Oscillograph.




Connect the test set to the CB.
Perform the following operations at the rated DCV.
Close ( C ) , Open ( O ) , Close - Open ( C – O ) & Open – Close – Open ( O – C – O )
Record the corresponding readings.
CB MAIN CONTACTS
CH. 1
R
CH. 2
Y
B
CH. 3
CLOSING ORDER
CB CLOSING TERMINALS
TRIPPING ORDER
CB TRIPPING TERMINALS
DC SUPPLY
+
-
CB TIMING TEST ARRANGEMENT
8. Check The Correct Functioning Of Interlocks And Limits Switches.