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Siemens 38-3AH3 38 kV Instruction Manual page 51

Vacuum circuit breaker
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Table 3: High-potential test voltages
Rated maximum-
Rated power-
frequency withstand
kV (rms)
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-
resistance 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. 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.
kV (rms)
kV (rms)
Insulation and contact-resistance test
In addition to the high-potential test
equipment capable of test voltages as
listed in Table 3, the following equipment
is required:
AC high-potential tester with test
voltage of 1,500 volts, 60 Hz
Test equipment for contact-resistance
Insulation and contact-resistance test
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
3. Apply the proper ac or dc high-
potential test voltage as shown in Table
3 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
6. Disconnect the leads to the spring-
charging motor.
Field-test voltage
kV dc
*Megger is a registered
trademark of Megger
Group, Ltd.



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