基于检测差流谐波含量的差动保护设计与实现

The design and implementation of differential protection based on current differential harmonic content

准确判断出电流互感器(CT)饱和是区内故障还是区外故障引起的,可提高差动保护的可靠性。分析了CT饱和产生的原因和故障时的差流波形,提出了一种基于差流谐波含量的差动保护方案。CT在过零附近区间能正确传变二次电流,通过分析这个区间的差流谐波含量,确定故障是否在差动保护的保护范围内。采用此方案,在发生区外故障CT饱和时能够可靠闭锁差动保护,在发生区内故障时能够快速开放差动保护。仿真结果验证了该方案的正确性。

Accurately determine current transformer( CT) saturation caused by internal or external fault will increase the reliability of differential protection. After analyzing cause of CT saturation and current differential waveform,a differential protection plan was indicated based on current differential harmonic content. CT is able to accurately transmit secondary current at zero passage. By analyzing the current differential harmonic content,the fault is in or out of the protection range will be determined.The simulation proved that,after applying this protection plan,external fault CT saturation will interlock differential protection effectively. Internal fault CT saturation will release differential protection rapidly.