Patent ID: 11965924
Assignee: VIKING PROTECTION SYSTEMS LLC
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 0:
1. A method for preventing ground fault or other short circuit in a three-phase electric transmission line system having at least three lines, caused by a break in a line, which comprises:
providing a programmable relay protection system, including a plurality of relay devices on each line of said electric transmission line system, said relay protection system being programmed to monitor changes in: low instantaneous undercurrent due to line changing current, small levels of negative sequence instantaneous overcurrent due to at least one phase being an open phase, instantaneous undercurrent due to less load being served, increased negative sequence instantaneous overcurrent due to load imbalance, and zero sequence instantaneous overcurrent and neutral line differential overcurrent, wherein said relay devices include:
a) preset parameter ranges multiple high sensitivity electric operating conditions, said preset ranges being acceptable operating parameter ranges, a first of operating conditions being instantaneous undercurrent, and a second of said operating conditions being selected from the group consisting of a) line differential overcurrent; b) negative sequence instantaneous overcurrent; c) neutral line differential overcurrent; d) zero sequence instantaneous overcurrent and e) combinations thereof;
b) monitoring each line at each of said plurality of relay devices for said at least two operating conditions, wherein said plurality of relay devices are programmed to be highly sensitive so as to monitor and measure instantaneous undercurrent in the range of 0.01 to 0.5 amp, so as to monitor and measure line different overcurrent in the range of 0.01 to 0.5 amp, so as to monitor and measure negative sequence instantaneous overcurrent in the range of 0.01 to 0.5 amp, as to monitor and measure neutral line differential overcurrent in the range of 0.01 to 0.5 amp, so as to monitor and measure zero sequence instantaneous overcurrent in the range of 0.01 to 0.5 amp, so as to monitor and measure and;
c) permitting closed circuit operation when all of said lines show said operating conditions are within said preset acceptable operating parameter ranges, said preset operating range for negative sequence overcurrent being 0.01 amps to 0.5 amps, and said preset operating range for instantaneous undercurrent being 0.01 amps to 0.5 amps;
d) when a line is broken, identifying a first monitor reading for undercurrent caused by instantaneous undercurrent below 0.5 amps; identifying a second monitor reading for instantaneous undercurrent caused by at least one phase being below 4.9 amps, after said first and second monitor readings, said third monitor reading for zero sequence overcurrent caused by load unbalance due to said broken line above 0.01 amps; identifying a fourth monitor reading for instantaneous undercurrent caused by undesired current imbalance of 0.1 amps to collectively sense a broken line;
e) tripping a circuit breaker on a broken line when a line shows said at least two operating conditions are outside said preset parameter ranges for all of said first and second and third and fourth monitor readings as set forth in paragraph d) above; such that said relay protection system communicates to open said circuit breaker on said broken line within 1.0 second, thereby shutting down power to said broken line before it otherwise causes a ground fault or other short circuit.