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Table 4: High-potential test voltages
Rated maximum voltage
kV (rms)
4.76
8.25
15.0
15.0 generator
circuit breaker
Vacuum-integrity test procedure
1. Observe safety precautions listed in the
DANGER and WARNING advisories.
Construct the proper barrier and warning
light system.
2. Ground the frame of the circuit breaker,
and ground each pole not under test.
3. Apply test voltage across each pole for
one minute (circuit breaker OPEN).
4. If the pole sustains the test voltage for
that period, its vacuum integrity has been
verified.
Note: This test includes not only the vacuum
interrupter, but also the other insulation
components in parallel with the vacuum
interrupter. These include the standoff
insulators and the insulated drive-links, as
well as the insulating (tension) struts
between the upper and lower vacuum-
interrupter supports. If these insulation
components are contaminated or defective,
the test voltage will not be sustained. If so,
clean or replace the affected components,
and retest.
As-found insulation and contact-resis-
tance tests
As-found tests verify the integrity of the
circuit breaker insulation system. Megger* or
insulation-resistance tests conducted on
equipment prior to installation provide a basis
of future comparison to detect changes in the
protection afforded by the insulation system.
Rated power-frequency withstand
kV (rms)
19
36
36
38
A permanent record of periodic as-found tests
enables the maintenance organization to
determine when corrective actions are
required by watching for significant
deterioration in insulation resistance, or
increases in contact resistance.
Insulation and contact-resistance test
equipment
In addition to the high-potential test
equipment capable of test voltages as listed
in Table 4: High-potential test voltages, the
following equipment is required:
AC high-potential tester with test voltage
of 1,500 volts, 60 Hz
Test equipment for contact-resistance
tests.
Insulation and contact-resistance test
procedure
1. Observe safety precaution listed in the
DANGER and WARNING advisories for the
vacuum-integrity check tests.
2. Close the circuit breaker. Ground the
frame of the circuit breaker, and ground
each pole not under test. Use manual
charging, closing and tripping procedures.
3. Apply the proper ac or dc high-potential
test voltage as shown in Table 4 between
a primary conductor of the pole and
ground for one minute.
4. If no disruptive discharge occurs, the
insulation system is satisfactory.
5. After test, ground both ends and the
center metal section of each vacuum
interrupter to dissipate any static charge.
6. Disconnect the leads to the spring-
charging motor.
Field-test voltage
kV (rms)
kV dc
14.25
20.2
27
38.2
27
38.2
28.5
40.3
*Megger is a registered
trademark of Megger Group,
Ltd.
51
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