GE Industrial Solutions Power-Vac ML-20 Mechanism - Manual (Page 14)

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SECTION 9—Electrical Checks
Electrical checking consists of electrical breaker operation
primary and secondary wiring high-potential testing (if
required), primary circuit resistance (if required). Interrupter
high-potential testing, and insulation resistance to ground.
9.1—Electrical Operation
To check the electrical operation, attach a secondary test
coupler to the circuit breaker connector. Check the control
voltage on the nameplate and close and open the breaker
several times.
CAUTION: REPEATED OPERATIONS AT A RATE EXCEED-
ING TWO PER MINUTE MAY CAUSE CHARGING MOTOR
OVERHEATING AND FAILURE.
9.2—High-Potential Test
If high potential tests to check the integrity of the primary
insulation is required, the AC high potential test described
below is strongly recommended. DC high potential testing is
not recommended. The following procedure must be adhered
to.
CAUTION: IF DC HIGH POTENTIAL TESTING IS REQUIRED,
THE DC HIGH POTENTIAL MACHINE MUST NOT PRODUCE
PEAK VOLTAGES EXCEEDING 50 KV.
NOTE: Always recheck with an AC tester if initial results are
questionable.
9.2.1 Primary Circuit
The breaker should be hipotted in the closed breaker mode.
An AC hipot machine capable of producing the test voltages
shown below may be used to hipot the breaker phase to
phase and phase to ground.
BREAKER VOLTAGE AC TEST VOLTAGE
27.0 kV 45 kV
The machine should be connected with its output potential at
zero and the voltage increased at 500 volts per second to the
test voltage and that voltage maintained for 60 seconds. The
voltage should then be returned to zero and the test leads
removed and the breaker discharged to ground. Do not
exceed the test voltage indicated.
If the test should experience a failure, STOP STOP STOP STOP, turn off the test
set and discharge the test sample. 1. Check the test setup
and leads for connection errors. 2. Wipe down the breaker to
remove any moisture, dust and contamination. 3. Retest the
breaker at the proper test voltage.
9.2.2 Secondary Circuit
Prior to hipotting the breaker secondary circuit, disconnect
the motor leads and thread a wire connecting all secondary
disconnect pins except #24, the ground pin. Connect the hipot
machine from this wire to ground. Increase the voltage to
1125 volts (rms) 60 Hz and maintain for 60 seconds. Reduce
the voltage to zero and remove the hipot machine from the
circuit. Remove the wire connecting the secondary disconnect
pins and reconnect the motor leads.
9.3—Primary Circuit Resistance
A resistance check of the primary circuit may be made
with the breaker closed. Use a low resistance measuring
instrument rated 100 amperes which measures in microhms.
The 100 ampere reading should be 25 or less microhms for a
600/1200 or 2000 amp. Breaker, when connected across the
upper and lower primary bars on the breaker side of the
disconnect fingers. Do not connect directly to the disconnect
fingers as errors may occur due to finger spring pressure
9.4—Vacuum Interrupter Integrity Test
NOTE: Use of a DC hipot is not recommended, but can be
used for quick field checks only. Always recheck with an AC
tester if initial results are questionable. Prior to performing any
vacuum interrupter integrity test, the outside (external
surface) of the vacuum interrupters should be wiped clean of
any contaminates with a non-linting cloth or industrial type
wiper. This is critical: the entire external surface is to be
completely free of all dirt, debris, dust, oil, etc.
CAUTION: X-RADIATION WILL BE PRODUCED IF AN
ABNORMALLY HIGH VOLTAGE IS APPLIED ACROSS A PAIR
OF ELECTRODES IN A VACUUM. X-RADIATION WILL
INCREASE AS VOLTAGE INCREASES AND/OR AS CONTACT
SEPARATION DECREASES. ONLY TEST A CORRECTLY-
ADJUSTED CIRCUIT BREAKER.
DURING A HIGH POTENTIAL OR A VACUUM INTEGRITY
TEST, ANY X-RADIATION WHICH MAY BE PRODUCED WILL
NOT BE HAZARDOUS AT A DISTANCE SAFE FOR HIGH
POTENTIAL TESTING, IF THE TEST IS CONDUCTED AT THE
RECOMMENDED VOLTAGE AND WITH THE NORMAL OPEN
CIRCUIT BREAKER GAP.
DO NOT APPLY VOLTAGE THAT IS HIGHER THAN THE
RECOMMENDED VALUE. DO NOT USE CONTACT SEPA-
RATION THAT IS LESS THAN THE RECOMMENDED OPEN-
POSITION BREAKER CONTACT GAP.
The vacuum integrity test is performed using an AC hi-
potential tester. A vacuum integrity test of the interrupter is
required to insure that no loss of vacuum has occurred. This
test of the vacuum interrupter will determine its internal
dielectric condition and vacuum integrity. With the breaker
open, individually check each interrupter by connecting the hi-
pot machine “Hot” lead to the upper primary bus bar and the
ground lead to the lower bus bar. If the machine has a center
point ground, the connections can be made either way. Apply
36 kV (rms) 60 Hz at 500 vps and hold for 10 seconds. If no
breakdown occurs, the interrupter is in acceptable condition.
After the high potential voltage is removed, discharge any
electrical charge that may be present through the internal