Earth fault detection method and device

Abstract

The embodiment of the invention discloses a ground fault detection method and device. The method comprises: a master station system calculates a transient current definite value of instantly discharging to the ground by the line when the single-phase earth fault happens and sends the single-phase earth fault transient current definite value to corresponding intelligent terminals; each intelligent terminal monitors the transient current value when the single-phase earth fault of the branch line phase line happens, and it is determined whether the transient current value is larger than the single-phase earth fault transient current definite value or not; and if the transient current value is larger than the single-phase earth fault transient current definite value, it is detected and determined whether the rate of decreased voltage on the branch line or the decreasing amplitude is larger than corresponding definite values or not, and if the rate of decreased voltage on the branch line or the decreasing amplitude is larger than corresponding definite values, it is determined that the single-phase earth fault happens. The ground fault detection method realizes the foreseeing capability for the fault line to instantly discharge to generate transient current when the single-phase earth fault of a distribution line happens, ensures reliable high-speed acquisition and calculation of the transient current when the single-phase earth fault of an electric line happens, so that the reliability and accuracy of the single-phase earth fault detection are fundamentally solved.

Description

technical field [0001] The invention relates to the field of electric power technology, in particular to a single-phase ground fault detection method and device of a neutral point non-ground power transmission and distribution system. Background technique [0002] The national 10KV distribution network system is mainly based on the neutral point non-grounded system (commonly known as the small current system, Y / Δ structure). When a single-phase ground fault occurs on the line, the symmetrical performance of the line remains unchanged, and the load current basically remains unchanged. Lines can continue to run for no more than two hours. However, the fault phase voltage drops and the normal phase voltage increases by √3 times, which seriously threatens the insulation performance of power distribution equipment, and is likely to cause equipment insulation breakdown and cause phase-to-phase short-circuit faults. Therefore, distribution network management units generally adopt a...

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Problems solved by technology

This method has also achieved certain results, but because of the need for a specific signal source, this signal source is not only very difficult to install and maintain, but also expensive, and what is more fatal is that it will bring serious safety hazards to the distribution network, so it cannot be promoted. and popularity

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