Fluorescence Fiber Based Identification of Partial Discharges in Liquid Nitrogen for High-Temperature Superconducting Power Apparatus

Partial discharge (PD) in liquid nitrogen (LN2) insulation is a key issue in cryogenic or high-temperature superconducting power apparatus. In this letter, we experimentally demonstrate PD identification in LN2using a fluorescent optical fiber sensor and compare its sensitivity to the conventional ultrahigh frequency (UHF) technique. The Corona inception voltage (CIV) in LN2is studied under fundamental ac and harmonic ac voltages with different values of total harmonic distortion (THD). It is observed that CIV reduces with the increase in harmonic voltage with higher THD. Phase resolved partial discharge pattern, peak-to-peak voltage, and the energy content due to corona discharges measured by both fluorescence-based and UHF techniques follows the same trend, indicating the viability of the new technique.