Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Patent
1981-03-30
1982-07-20
Eisenzopf, Reinhard J.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
191 8, 361 42, H02H 300
Patent
active
043409202
ABSTRACT:
A mine safety system for use with a direct current power supply delivering power via a pair of conductors to the direct current load components of mining apparatus which includes a conductive frame electrically isolated from ground and at least one of the conductors. In the safety system, an alternating current generator transmits a predetermined frequency signal over the pair of conductors to the mining apparatus. A filter which passes the predetermined frequency signal is disposed at the mining apparatus in a shunt circuit with the load components, the filter thereby being connected to the generator. Circuitry monitors the impedance of the electrical load on the generator at the predetermined frequency and a contactor responsive thereto stops the delivery of power from the power supply to the mining apparatus upon the impedance of the electrical load on the generator at the predetermined frequency exceeding a predetermined level which exceeds the impedance of the shunt combination of the filter and load components. Switching circuitry disconnects the filter from the generator in response to the flow of significant current from one of the conductors to the mining apparatus frame, thereby increasing the impedance of the electrical load on the generator at the predetermined frequency to above the predetermined level, whereby delivery of power from the power supply to the mining apparatus is stopped.
REFERENCES:
patent: 1324903 (1919-12-01), Klink
General Informaltional Materials on Femco GM 1000 Ground Sentinel II, 2/3/76, National Mine Service Co., Pittsburgh, PA.
Schematic of ground monitor system for A.C. power systems utilizing Femco Ground Sentinel II.
Gill Ronald P.
Hull, Jr. John E.
Tucker Dempsey G.
Eisenzopf Reinhard J.
Peabody Coal Company
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