PROTECTIVE AUTOMATICALLY DISCONNECTABLE GROUPING MEANS FOR AN UNGROUNDED A.C. ELECTRICAL DISTRIBUTION SYSTEM

摘要

An ungrounded a.c. electrical distribution system is provided with a protective grounding device in circuit with means for automatically disconnecting the grounding device in the event that a fault to ground occurs on any line of the system. The grounding device can be a transformer having a neutral grounded point. The automatic disconnection means may be circuit breakers or current limiting fuses and may further include a relay assembly having automatically opening contacts. The relay assembly can be thermally operable. The transformer can be a zig-zag transformer. External signal devices can be connected to the relay assembly.