电气回路谐波电流引发中性线热故障的探讨

随着我国经济建设的快速发展和人民生活质量的提高,各种场所的用电负荷需求量越来越大,电脑、空调等家用电器的普及,高智能化的楼宇办公自控装置引进,非线性负载的比例逐渐增大.尤其发生在竣工通电试运行中断路器莫名其妙跳闸,操作者往往怀疑操作有误或接线不正确,盲目地去查找故障点,当用钳型电流表对跳闸回路电流测量,其测量结果发现,电流值并未超出断路器的整定值.又如：消防电气检查中,许多记录记载着零线电流大于相线电流,有的甚至超出2倍,观感中性线表面有烧焦.什么原因引起的中性线发热？能不能预防或采取什么措施能避免这些不安全的事情发生,一直是疑点.本文从非线性负载的谐波电流问题入手,从理论波形分析到案例中反映的实际问题,综合分析系统存在非线性负载时和不存在非线性负载时电压电流的变化过程及对运行中系统的危害,同时兼顾分析低压配电系统处于三相平衡状态或三相不平衡状态时,谐波电流在回路中的厉害关系,以及设计方面、施工过程工艺操作质量控制因素等,一并分析找出引发中性线热故障的原因,提出预防中性线过载发热的措施与建议.

Discussion of Harmonic Current in Electric Return Circuit Cause of Thernal Fault on Neufral Conductor

Based on thorelical analysis of wave form, this paper explained the uariation of uoltage and current and it's harmfulness caused by harmonic current in the power supply system with nonlinear load or nat. The paper also analised The effect of hormonic curreat on circuit when the low valtage clistribution system is in Three-phase balance or not, and found out the cause of thernal fault on neufral conductor and put foreward the proposalo to profeet overload heat from the conductor