Abstract: A system for preventing ground fault or other short circuit in electric distribution line system, caused by a break in a line, utilizing programmable relay protection in a plurality of relay devices programmed to monitor high sensitivity parameters, includes blown fuse protection in a single phase tap line to prevent false operation of the open conductor logic when a tap line fuse successfully interrupts a short circuit on the tap line, which includes: blown fuse protection subsystem having relay devices on the tap lines (vis transformers) that have microprocessors programmed to detect changes in negative sequence overcurrent on a single phase tap line, to calculate the change in negative sequence overcurrent, to store a preset acceptable range for change of negative sequence overcurrent, to compare the calculated change in negative sequence overcurrent to the preset acceptable range for change of negative sequence overcurrent.

Abstract: A device for preventing ground fault in electric distribution lines caused by a break in a line, utilizing programmable relay protection in a plurality of relay devices with microprocessors, programmed to monitor high sensitivity parameters, the device having refined protection, which includes: in MODULE A, programmed to detect changes in negative sequence overcurrent and instantaneous undercurrent on main distribution lines or single phase tap lines, utilizing a timer delay to calculate changes over small time periods. Second and third embodiments include substituting negative sequence with zero sequence readings in MODULE B or combining both MODULES A and B.

Abstract: In a system for preventing ground fault or other short circuit in electric distribution line system, caused by a break in a line, utilizing programmable relay protection in a plurality of relay devices programmed to monitor high sensitivity parameters, the improvement of refine protection, which includes: in MODULE A, a protection subsystem having sufficient hardware and software that is programmed to detect changes in negative sequence overcurrent and instantaneous undercurrent on a main distribution line as well as a single phase tap line, utilizing a timer delay to calculate the changes over small periods of time. Second and third embodiments include substituting negative sequence with zero sequence readings in MODULE B or combining both MODULES.

Abstract: In a system for preventing ground fault or other short circuit in electric distribution line system, caused by a break in a line, utilizing programmable relay protection in a plurality of relay devices programmed to monitor high sensitivity parameters, the improvement of blown fuse protection in a single phase tap line to prevent false operation of the open conductor logic when a tap line fuse successfully interrupts a short circuit on the tap line, which includes: blown fuse protection subsystem having sufficient hardware and software that is programmed to detect changes in negative sequence overcurrent on a single phase tap 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.

Abstract: A system for preventing ground fault in a three-phase electric distribution line system caused by a line break, includes: the transmission lines, a programmable relay protection system, including high sensitivity. The HS relays on each line are programmed to include: preset acceptable operating parameter ranges of at least two electric operating conditions, namely, high sensitivity instantaneous undercurrent and at least one high sensitivity negative sequence overcurrent; monitoring; permitting closed circuit operation when all of the lines show that the two operating conditions are within the preset acceptable operating parameter ranges; tripping a circuit breaking device on a broken line when that line shows that the two operating conditions are outside the preset parameter ranges; and shutting down power to the broken line before it otherwise causes a ground fault or other short circuit. A third parameter monitoring: rate of change in current is preferred.