Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Patent
1977-02-15
1979-05-08
Salce, Patrick R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
324 51, 340649, 340652, H02H 510
Patent
active
041539230
ABSTRACT:
A system for monitoring the continuity of at least the ground wire of a cable connected between a mining machine and a power center. At the power center, a monitor signal is coupled to multi-phase power conductors of the cable through a multi-phase filter. The monitor signal from the conductors is coupled to the ground wire at the mining machine through another multi-phase filter. The signal returns through the ground wire to the power center where a current transformer couples the signal from the ground wire to a receiver. The receiver which receives and senses the characteristics of the returned signal includes parallel phase locked loop discriminators to prevent false tripping of the main power breaker if the monitor frequency should vary only slightly. The parallel discriminators provide a fail safe arrangement to prevent the main power breaker from remaining closed if one of the parallel discriminators should malfunction. A decrease in amplitude or change in frequency beyond a pre-selected range of the monitor signal at the receiver discontinues the receiver output so the main power breaker will open and cut off the A-C power to the mining machine.
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Mouzavires William E.
Salce Patrick R.
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