Comparison of capacitive and inductive sensors designed for partial discharges measurements in electrical power apparatus

Abstract

Abstract. In the paper results of simultaneously conducted measurements achieved using capacitive and inductive sensors are presented according to different PD model sources immersed in a mineral transformer insulation oil. All measurements are preceded under laboratory conditions using typical measurement set up commonly applied for on-site PD detection: measuring impedance and capacitor and high frequency current transformer (HFCT) are used respectively. Measuring frequency and voltage level influence as well as phase resolved PD patterns analysis are investigated in the research. Various fundamental PD signal descriptors assigned for selected frequencies are also proposed and compared for chosen sensors. The main purpose of the presented research is to compare PD measurement results achieved using selected type of sensors during laboratory measurements and to point the best application areas in fields of PD detection in high voltage apparatus under normal operating conditions. Furthermore a proper measurement results interpretation coming from different sensors as well as measurement conducting problems and achieved patterns disparities are also discussed in the paper.

Analysis of the spectrum of electromagnetic radiation generated by electrical discharges

“…The effectiveness and precision of this method was confirmed in many publications, e.g. [5][6][7][8][9][10]. Other equally effective, frequently used and constantly developed methods are chromatographic or spectrometric analysis of gases dissolved in oil (DGA) analysis, acoustic emission and ultra-high frequency (UHF) methods [11][12][13][14][15][16][17][18].…”

On-Line Partial Discharge Monitoring System for Power Transformers Based on the Simultaneous Detection of High Frequency, Ultra-High Frequency, and Acoustic Emission Signals

“…It should be emphasized that for the HFCT sensors devoted to PD detection, the more important parameter than the f L is higher −3 dB cutoff frequency f H , since the discharges in oil-paper insulation emit high-frequency waves mainly in the range between approx. 2 and 20 MHz [98]. In this case, it is more favorable to apply a lower number of turns.…”

Variability of the UHF Signals Generated by Partial Discharges in Mineral Oil

“…Furthermore, different attenuations of the signals are also related to those materials. For example, in case of oil-filled power transformers signals measured in galvanic parts using electrical method (capacitive or inductive sensors), are influenced by the inductivity of every turn of the winding coil and all stray capacities which works as a low pass filter, thus a measured upper-frequency limit is typically limited to approximately tens of MHz [33]. The propagation of the electromagnetic signals inside of the transformer tank is a radiated emission in the entire volume of the transformer, in oil and pressboard.…”