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Ground fault protective systems with predetection neutralization of reactive currents

  • US 4,138,707 A
  • Filed: 07/21/1977
  • Issued: 02/06/1979
  • Est. Priority Date: 07/21/1977
  • Status: Expired due to Term
First Claim
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1. A ground fault protective system for use with a power distribution system for supplying a.c. power to a known load from at least two supply conductors, at least one of said supply conductors exhibiting a measureable downstream reactance to ground giving rise to net reactive differential currents in said supply conductors not characteristic of a real ground fault comprising:

  • differential current sensing means responsive to currents in said supply conductors for generating fault signals representing differential currents carried by said supply conductors; and

    neutralizing means comprising at least one auxiliary circuit branch including predetermined impedance means so connected to at least one of said supply conductors and proportioned relative to said downstream reactance to ground as to exert a neutralizing effect on said net reactive differential currents substantially counterbalancing the effect on said fault signals of said downstream reactance to ground.

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