30 CFR § 75.800-3
Testing, examination and maintenance of circuit breakers; procedures.
(a) Circuit breakers and their auxiliary devices protecting
underground high-voltage circuits shall be tested and examined at least once
each month by a person qualified as provided in §75.153;
(b) Tests shall include: (1) Breaking continuity of the ground check
conductor, where ground check monitoring is used; and
(2) Actuating at least two (2) of the auxiliary protective
relays.
(c) Examination shall include visual observation of all components of
the circuit breaker and its auxiliary devices, and such repairs or
adjustments as are indicated by such tests and examinations shall be carried
out immediately.