An over-voltage protection scheme of power capacitor bank exposed to harmonic

This paper analyzed the defects of the most conventional protections of the capacitor when voltage waveform distortion is serious, and the effects on the protections of voltage signal selection in harmonic case. These defects may cause tripping failure or mal operation of protection in serious harmonic condition. Then this paper researched the influence of harmonics on capacitor life by an experiment and analyzed the relationship between the change of capacity value and voltage rms (root mean square), peak and waveform factor before and after the test. According to the capacitor over-voltage protection defects and combined with capacitor test results, this paper proposed an over-voltage protection scheme based on voltage peak and waveform factor. This scheme retains the original rms over-voltage protection, adds protection strategy aimed at voltage peak and waveform factor and a concrete proposal is given to realize the specific protection. By this method, capacitor bank could be protected effectively.