×

Sub-cycle digital distance relay

  • US 5,453,903 A
  • Filed: 08/18/1993
  • Issued: 09/26/1995
  • Est. Priority Date: 08/18/1993
  • Status: Expired due to Term
First Claim
Patent Images

1. A protective relay apparatus for providing a trip signal to a circuit breaker on a three-phase electrical power transmission line in an AC electrical power transmission system when a fault is detected in a protection zone of the circuit breaker, comprising:

  • sampling means for providing samples A(1) to A(N) of at least one of voltage and current for each cycle of a power signal on said transmission line; and

    a processor responsive to said samples A(1) to A(N) for determining whether said fault is in said protection zone and hence whether said circuit breaker should be tripped, said processor implementing a full cycle Fourier algorithm which extracts the fundamental power line frequency phasor components from those samples A(1) to A(N) sampled by said sampling means after detection of said fault, said processor comprising means responsive to said sampling means for (1) providing samples A(1) to A(N/2) sampled by said sampling means after detection of said fault to said full cycle Fourier algorithm as samples A(1) to A(N/2), (2) calculating artificial samples A(N/2+1) to A(N) in accordance with the equation;

    A(k)=(-1) , A(k-N/2), k=N/2+1 to N, and (3) providing said artificial samples A(N/2+1) to A(N) to said full cycle Fourier algorithm as samples A(N/2+1) to A(N), whereby said processor provides said trip signal to said circuit breaker when said full cycle Fourier algorithm determines from said samples A(1) through A(N/2) and artificial samples A(N/2+1) through A(N) that said fault occurred in said protection zone.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×