Breaking the limit of power capacitor resonance frequency with help of PD pulse spectrum to check and setup PD measurement.

Summary

Partial discharge (PD) measurement is often performed without prior validation of the calibration pulse spectrum. In most cases, the correct frequency range for PD measurement is well known but measuring the pulse spectrum is a means to verfiy that the PD filter limit frequencies (f1, f2) fit the quasi-integration requirement according to IEC 60270. The pulse spectrum assists to detect wrong connections and defective parts as well as to verify the efficiency of HV noise suppression filters. In case of power capacitors, the resonance frequency is an essential parameter to correctly set the PD measurement frequencies in order to achieve adequate sensitivity as well as compliance with IEC 60270. This paper covers the theory and practical Information required to set the correct PD frequency range with respect to the power capacitor resonance frequency. It demonstrates that PD measurement with limit frequencies set beyond the resonance frequency of the power capacitor is possible if an identical capacitor is used as the PD coupling capacitor. Sensitivity issues when using bridge connections are discussed and PD detector and coupling impedance requirements are equally covered.

Additional informations

Authors

Wattanawongpitak Sarawut, Ruankon Sayan, Suwanasri Cattareeya, Lipirodjanapong Sumate