Siemens 38-3AH3 38 kV instruction manual Field-test voltage, Voltage Frequency withstand

Maintenance

Table 3: High-potential test voltages

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

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.

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.