Partial Discharge Electrical Tree Growth Identification by Means of Waveform Source Separation Techniques

Carlos Madariaga,Osvaldo Munoz,Roger Schurch,Jorge Ardila-Rey,Sebastian Fingerhuth

doi:10.1109/access.2021.3075914

Abstract

Electrical trees are one of the main degradation processes leading to failure of high voltage polymeric insulation. Electrical trees grow under the effect of partial discharges (PD), which can be measured and analyzed for condition monitoring of electrical insulation. In this paper, techniques that are normally used for classification of PD and noise separation were explored in their ability to determine the stage of growth of electrical trees: Spectral Power Clustering Technique (SPCT), Time-Frequency (TF) maps and Chromatic Technique (CT). The techniques allowed to analyze PD signals captured in ultra-high frequency (UHF) range with an antenna during tree growth. Laboratory treeing-samples were made of epoxy resin and trees were generated at six different excitation frequencies: 0.1, 10, 50, 150, 250 and 350 Hz. The results showed that two parameters, part of SPCT and TF maps, were sensitive to the tree progression and showed a consistent relation with the length of the tree: the low-frequency power ratio and the equivalent bandwidth. These two parameters were selected to create a new map, proposed for the characterization of electrical tree growth, which is more consistent and robust than the original separation maps. It was found that the low-frequency content of PD pulses proportionally increased with tree propagation.

Highlights

One of the main degradation mechanisms in high voltage polymeric insulation systems of electrical equipment is the formation of electrical trees inside the material [1], [2]
The shape of the electrical tree structures varied depending on the applied frequency and voltage, consistent with what has been reported in the literature [24]
The results showed that the centroid of the PR maps moved as the tree grew, indicating that Spectral Power Clustering Technique (SPCT) is sensitive to the progression of the tree

Summary

Introduction

One of the main degradation mechanisms in high voltage polymeric insulation systems of electrical equipment is the formation of electrical trees inside the material [1], [2]. Electric trees can be considered as microscopic tubular structures composed of gas channels that branch beyond their place of origin, eroding the insulation and causing equipment failure [1]. The growth of electric trees is associated to internal PD activity that takes place in the areas where these channels or branches are formed. In this regard, PD measurement has proven to be a. One of the main advantages of using VHF-UHF sensors is the feasibility of capturing PD activity without requiring galvanic contact with the equipment being monitored

Methods

Results

Discussion

Conclusion