US 12,449,465 B2
Electric distribution line ground fault prevention device using dual parameter high sensitivity monitoring small current reduction with small increase in negative sequence current
Robert B. Stuart, San Tan Valley, AZ (US)
Assigned to Milo Group LLC, Casper, WY (US)
Filed by Robert B. Stuart, San Tan Valley, AZ (US)
Filed on Oct. 19, 2024, as Appl. No. 18/920,865.
Application 18/920,865 is a continuation in part of application No. 18/464,596, filed on Sep. 11, 2023, abandoned.
Application 18/464,596 is a continuation in part of application No. 18/448,914, filed on Aug. 12, 2023, abandoned.
Application 18/448,914 is a continuation in part of application No. 18/064,152, filed on Dec. 9, 2022, granted, now 11,852,692.
Prior Publication US 2025/0044338 A1, Feb. 6, 2025
Int. Cl. G01R 31/08 (2020.01); G01R 31/52 (2020.01); H02H 7/26 (2006.01)
CPC G01R 31/085 (2013.01) [G01R 31/52 (2020.01); H02H 7/26 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A device for preventing ground fault or other short circuit in an electric distribution line system caused by a break in a line of said electric distribution line system, wherein said system includes a four-line distribution circuit, and said system includes a plurality of current transformers with relay devices functionally connected to said transformers by being connected to secondary stepdown windings of said current transformers, said relay devices being for monitoring high sensitivity parameters on said four line distribution circuit, which comprises:
said device being a relay device for said four-line distribution circuit, having a housing, and having connections with an incoming line and an outgoing line for connection to a current transformer on said four-line distribution circuit, and having a plurality of monitors, and having a programmable microprocessor functionally connected to said monitors, said programmable microprocessor being programmed for micro-monitoring segments of a line as follows:
a) to detect changes in instantaneous undercurrent on said distribution line, to calculate the change in instantaneous undercurrent, to store a preset acceptable range for change of instantaneous undercurrent, to compare said calculated change in instantaneous undercurrent to said preset acceptable range for change of instantaneous undercurrent;
b) to detect changes in negative sequence overcurrent on said distribution line, to calculate the change in negative sequence overcurrent, to store a preset acceptable range for change of negative sequence overcurrent, to compare said calculated change in negative sequence overcurrent to said preset acceptable range for change of negative sequence overcurrent; and,
c) if the calculated change in instantaneous undercurrent is outside said preset acceptable range for change of instantaneous undercurrent, and, if the calculated change in negative sequence overcurrent is outside said preset acceptable range of change of negative sequence overcurrent, then there is a true line break fault and the high sensitivity monitoring proceeds to signal a true line break fault for line shut down of the monitored line.