Maintenance – Siemens vacuum circuit breaker 38-3AH3 38 kV User Manual

Page 51

Maintenance

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.

Rated maximum-

voltage

Rated power-

frequency withstand

Field-test voltage

kV (rms)

kV dc

38.0

Table 3: High-potential test voltages

Insulation and contact-resistance test
equipment

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
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
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
charge.

6. Disconnect the leads to the spring-

charging motor.

*Megger is a registered
trademark of Megger
Group, Ltd.