知识与财富的链接
电快速瞬变脉冲群干扰(EFT/B)是微机保护装置最易受到影响的干扰之一,当干扰水平超过了装置逻辑元件和逻辑回路的抗干扰水平时,将引起装置不正常工作或程序运行出错。通过一个微机保护装置受到干扰导致频繁重启的实例,采用实验的方法分析并查找出了继电器触点弹跳是产生本例EFT/B干扰的主要原因,通过更换不同型号的继电器减少了EFT/B干扰的耦合程度,可靠抑制了EFT/B干扰。还根据国际IEC和IEEE标准对EFT/B波形进行了理论分析,在拉普拉斯变换和傅里叶变换的基础上通过几种不同方法计算了EFT/B波形的频谱,给出了工程实践中既简单又合理的计算方法,并试图通过分析EFT/B波形的频谱分布,使得对EFT/B的电磁干扰的防护更具有针对性。
The electrical fast transient/burst(EFT/B) disturbance is one of the most important transient electromagnetic disturbances which influence the microprocessor-based protection.The relay will fall into failure and its procedure will make an error if the EFT/B disturbances exceed the immune capability.An instance of digital relay abnormally reboot as a result of EFT/B,which is produced by electric magnetic bounce of relay,is presented in this paper.By changing the type of the relay,the electromagnetic coupling is decreased and the disturbance is effectively restrained.The EFT/B waveform is analyzed and its spectrum is calculated by different methods based on LT and FT.The theory and frequency-spectra distribution of EFT/B is also analyzed,simple and sound calculation methods are given which help us to restrain the EFT/B in digital relay.
