Positioning of Partial Discharge Origin by Acoustic Signal Detection in Insulation Oil

Abstract

Abstract – In this paper, we performed an insulation diagnosis technique for oil-immersed power transformers by an acoustic detection method. Acoustic signal detection circuit was designed and fabricated to detect acoustic signal with high sensitivity. Electrode system such as needle to plane electrode was fabricated to simulate a defect of oil-immersed power transformers. We could find the position of the partial discharge (PD) source in 3-dimension with an error margin of 4 % in the experiments by calculating the position of the PD occurrence using the time difference of arrival measured by five AE sensors. Keywords : Acoustic detection, Partial discharge, Insulation diagnostic, Frequency component, Positioning 1. Introduction Research on insulation diagnostic techniques is being actively carried out because of the increasing demand for high quality power, which power facility owes its high voltage and large capacity to. Electrical insulation is an important factor in the performance of power facility; however, the insulation performance of the power facility decreases because of mechanical, thermal, chemical, and electrical stress [1], [2]. As power transformer accidents cause large outage areas and are expensive to repair, on-line monitoring and periodic diagnosis of the stability of the power supply is required [3]–[7]. A recent important technique for insulation diagnosis is the partial discharge (PD) detection method, which can detect insulation deterioration in its early stages because there is a concentrated electric field in the defective area of an insulation material i.e., where PD occurs [8]–[10]. PD detection can be divided into two methods: one, electrical, the other, non-electrical. The electrical method has high sensitivity, which enables precise measurement. However, some of the shortcomings of this method include the fact that it is likely to be affected by electromagnetic noise and coupling network can’t be installed during operation. The nonelectrical method includes acoustic, optical, and chemical detection. The acoustic detection method has low sensitivity compare to the electrical method [11]. This method, however, is less likely to be affected by electromagnetic noise as it is electrically insulated. Additionally, the acoustic emission (AE) sensor can be installed easily during operation. Also, positioning of the defect is possible by measuring the time difference of arrival (TOA) of the acoustic signal using multiple sensors [12]. This paper dealt with the application of the acoustic detection method for the insulation diagnostics of oil-immersed power transformers. Moreover, 3-D positioning of the partial discharge was studied.