畸变电流下的电子脱扣器校准误差分析

Calibration error analysis of electronic trip unit under distorted current

畸变电流会引起电子脱扣器误动作,进而导致低压断路器无故跳闸。利用峰值系数KP和波形系数KW,分析了三角波和矩形波这两种典型的畸变电流波形对不同电流检测及控制处理方式电子脱扣器的影响,克服了谐波电流总畸变率(THD)难以准确、定量分析谐波电流对电子脱扣器校准误差影响的缺陷。通过峰值检测校准误差曲线和均值检测校准误差曲线可以准确、直观地看出不同畸变波形下峰值检测和均值检测的校准误差。根据非线性负荷的波形特征及校准误差曲线,适当地调整动作电流整定值,能够在一定程度上避免畸变电流导致的电子脱扣器频繁误动作现象。

Distorted current causes the electronic trip unit malfunction, which results in low-voltage circuit breaker＇s tripping without fault. To analyze the effect of two typical distorted waveforms, triangular wave and square wave, on the electronic trip unit with different current detection and control methods, the peak coefficient Kp and waveform coefficient Kw are used. The defect that total harmonic distortion （THD） can＇t be used to analyze the harmonic current impact on the electronic trip unit＇s calibration error correctly and quantitatively is overcome. The calibration error can be seen accurately and intuitively through the calibration error curve of peak value detection and mean value detection. According to the nonlinear load＇s waveform characteristic and calibration error curve, the frequent malfunction of electronic trip unit caused by distorted current can be avoided in a certain extent by adjusting the action current setting value properly.