A protective system that operates as a result of leakage of current from
electrical machines to earth. For electrical apparatus in mines, the usual
method of leaking protection is known as the core balance system. This
depends for its action on the balance of the currents in three phases.
When a fault occurs, the balance is disturbed and the resulting magnetic
effect in the transformer core induces a current in the secondary circuit,
so energizing the tripping coil and operating the tripping mechanism on
the circuit breaker. It may be operated by a leakage current as low as 5%
of the full load current of the circuit. Nelson
Source: Dictionary of Mining, Mineral, and Related Terms
