MIL-HDBK-1025/10
Table 25
Grounding of Substation Equipment
I.
Tanks. Grounds should be in place (see Table 26) before a tank is opened and the
insulating medium (oil/gas) is changed. This does not apply to sampling.
III. Capacitors.
A. Allow at least 5 minutes between opening of the capacitor switching devices and the
closing of the ground switch on a fully charged capacitor bank.
B. Allow at least 5 minutes after the ground switch is closed before installing protective
grounds.
C. A capacitor bank should remain de-energized for at least 5 minutes before it is re-
energized.
D. The time required for these maneuvers should be explicitly expressed in switching
orders involving capacitor banks.
IV. Surge arresters. Surge arresters should be disconnected and discharged using grounding
cables.
energized and properly grounded. Phase reactors should be isolated from all energized
sources and grounded before being worked on.
VI. Bushings.
A. Bushing leads may be disconnected from bushing terminals as necessary to permit
equipment testing that requires the equipment to be ungrounded.
B. Use a hot stick to connect test equipment and re-establish the ground as soon as the
test is completed.
C. Following an applied potential test ("Hi-Pot"), ensure the ground remains in place for a
period at least two times the duration of the test period.
D. Work clearances and grounding instructions for the test equipment will be in
accordance with the manufacturer's recommendations.
VII. Separate grounds. Install separate grounds for each isolated section of the de-energized
circuit if a hazard exists when working in a de-energized area of a substation where there is
one or more physical breaks in the electrical circuit.
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