TESTING AND COMMISSIONING : TESTING OF CIRCUIT BREAKERS
1 . Insulation Resistance Measurement :- By 1KV to 5 KV (DC) Megger. Measure IR value between pole to Earth (when CB is open). IR value of HV CB is very high above 1000 Meg ohm.
IR value of control, circuit, trip circuit, relay circuit, and secondary circuit is measured by 500V megger
value should not be less than 1 Meg-ohm.
2 . Contact Resistance Measurement : – Compared with factory results. Contact Resistance of breaker pole in on the range of 40 micro ohm to 120 micro ohms.
A Contact resistance is measured by
(a) Micro ohm meter
(b) by DC voltage drop for different current.
3 . Breaker opening and closing Time measurement :-
Opening time normally in the range – 30 millisec – 50 millisec.
Closing – 60 milli sec 120 mili sec.
4 . Minimum Trip Coil Voltage :- Minimum DC Voltage at which breaker will trip. Usually trip coils operate correctly even if the voltage at the trip coil terminal in 50% of rated DC voltage.
5 . Breaker Analyser tests : – By breaker analyzer the following parameters can be known:
(a) Current taken by trip coil, closing coil.
(b) Condition of contact in side
(c) Trip time, close time, trip-close, close open times
(d) Travel, velocity of the trip contact pole etc.
6 . Functional and Non-Electric Tests : TESTING OF CIRCUIT BREAKERS
- Moisture content and air content measurement of SF, gas.
- Oil condition in case of MOCB.
- Correct operation of pressure switches.
- Oil / Air pressure settings in pressure switches.
- Pump control in case of ABCB
- Auto reclosure lock out pressure checkup lower pressure in the accumulator until pressure monitor activate the auto reclosure lockouts via contactors respectively. Read the operating values on the test gauge check the indications and also the effectiveness of autoreclosure lockouts by impartingelectrical close/trip command. The C.B. must not operate.
- Checking the tripping facilities.
- Checking of general lockout.
- Checking the anti pumping feature.
- Checking of anticondensation heather, oil level in pump accumulator release lock etc. to be carried out.
Also Read : TESTING AND COMMISSIONING
Also Read : ELECTRICAL FAULT FINDING