Study of a Fluorescent Optical Sensor for DC Partial Discharge Under Different Wavelength Shifting Materials

Optical measurement technology plays a crucial role in High-Voltage (HV) applications, particularly for detecting Partial Discharges (PD). Recently, researchers have advanced the field by using fluorescent Polymethylmethacrylate (PMMA) optical fiber elements to identify PD phenomena. This is achieved through fluorescence measurements, where fluorescent materials are excited by ultraviolet (UV) emission or visible light (VIS) from the PD or arc. Despite the challenge of measuring low optical effects, fluorescence detection has become highly sensitive due to the amplification of single photons via photomultipliers. This paper presents an innovative method for distinguishing discharge processes based on the pulse shape at different PD patterns and different voltage polarities. A novel optical sensor geometry presented in this paper allows the entire light-sensitive area of the Silicon Photo Multiplier (SiPM) to efficiently detect the photons emitted by the PMMA prism. Experiments with three PMMA colors - red, green and blue - show that blue PMMA generates the highest signal amplitude at the oscilloscope input, followed by green and then red. The focus here is on matching the emission spectrum of the partial discharge, the absorption and emission spectrum of the fluorescent material and the absorption spectrum of the SIPM. As a result, the mismatch between the SiPM and the fluorescent material can also be specifically utilized to develop a PD criterion for DC-PD, where phase-resolved PD detection is not applicable.