Current increment protection method capable of reflecting mean current change rate

Abstract

The invention discloses a current increment protection method capable of reflecting a mean current change rate. The method comprises the following steps of: sampling feeder line current by an isolation amplification unit to obtain an instantaneous current value by using a metro DC feeder line protection device; filtering a high frequency component by using a digital filtering algorithm, and calculating an actual current value; when current increment in a sampled data window exceeds a set starting value, starting protection, and stating performing timing by using an exit timer; calculating a current change rate in a time period from 20ms before the protection is started to 20ms after the protection is started, and if the current change rate exceeds a set value, and is kept for longer than 20ms, arranging an increment protection enable flag; and when the time of the exit timer exceeds a set increment protection time value, and the current increment is not lower than a set increment protection returning value, and is provided with the increment protection enable flag, protecting an exit to be tripped. By the method, the mean current change rate in the time period is reflected, and is stable, reliable and not fluctuated along with the fluctuation of current change rates.

Description

technical field [0001] The invention belongs to the technical field of current system relay protection, and in particular relates to the protection of a subway direct current power supply system. Background technique [0002] First, the related art of the present invention is briefly described based on the following references. [0003] 1) Ding Fuhua, "Electrical Protection and Valuation of Subway DC Traction Power Supply System", Metropolitan Rapid Transit, 2005, 18(4). [0004] Document 1) introduces a current incremental protection method. The protection has three parameters ΔI, Δt, t. Within Δt time, when the current increment reaches ΔI, a timing signal is issued. When the current increment is not less than ΔI and the time reaches t, a trip command is issued. This method can adapt to various fault current waveforms, has a wider protection range, and has stronger anti-interference ability and better selectivity. When a fault occurs in the train car, it can play a re...

AI Technical Summary

Problems solved by technology

[0006] In order to solve the problems of protection refusal and misoperation due to large fluctuations in the rate of current change, and to avoid protection misoperation during step waveforms, this invention proposes a current incremental protection method that reflects the average current change rate

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