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48
PowlVac® CDR 27kV &38kV Vacuum Circuit Breaker
IB-65020A
Maintenance
3) Primary Resistance Check
This check is not required for routine
maintenance but it is recommended after
any major maintenance that requires
disassembly of any part of the primary
current path.
To check the primary resistance, pass a
minimum of 100A DC through the circuit
breaker pole, with the circuit breaker
closed. Measure the voltage drop across
the primary contacts and calculate
the resistance. The resistance should
not exceed the values provided in this
instruction bulletin for the specific type
and rating of the circuit breaker being
measured.
When making this test, be sure that the
test current passes through both main
horizontal primary disconnecting devices
of each pair, or the resistance measurement
will be affected. This may be done by
connecting the current source leads to two
blocks of full round edge copper 1” thick
by 3” or 4” wide by 4” long, and pressing
these blocks into the upper and lower
primary disconnecting devices of the circuit
breaker compartment. The voltage drop
measurement may be made between these
two blocks.
The micro-ohm values of resistance must
not exceed the limits in
Table D, Primary
Resistance
.
Table D Primary Resistance
Breaker
Type
Rated
(kV)
Continuous
Current
(Amperes)
Resistance
(Micro-ohms)
27PV25CDR
27
1200
40
27PV25CDR
27
2000
36
38PV40CDR
38
1200
46
38PV40CDR
38
2000
36
