Pattern Recognition of Development Stage of Creepage Discharge of Oil–Paper Insulation under AC–DC Combined Voltage Based on OS-ELM

Fubao Jin,Yuanxiang Zhou,Shanjun Zhang

doi:10.3390/en14030552

Abstract

The recognition of the creepage discharge development process of oil–paper insulation under AC–DC combined voltage is the basis for fault monitoring and diagnosis of converter transformers; however, only a few related studies are available. In this study, the AC–DC combined voltage with a ratio of 1:1 was used to develop a recognition method for the creepage discharge development process of an oil–paper insulation under a cylinder–plate electrode structure. First, the pulse current method was used to collect the discharge signals in the creepage discharge development process. Then, 24 characteristic parameters were extracted from four types of creepage discharge characteristic spectra after dimensionality reduction. Finally, based on the online sequential extreme learning machine (OS-ELM) algorithm, these characteristic parameters were used to recognize the development stage of the creepage discharge of the oil–paper insulation. The results showed that when the size of the sample training set used in the OS-ELM algorithm is close to the number of hidden layer neurons, a high recognition accuracy can be obtained, and the type of activation function has little influence on the recognition accuracy. Four stages of the creepage discharge development process were recognized using the OS-ELM algorithm; the trend was the same as that of the characteristic parameters of the entire creepage discharge development process. The recognition accuracy was 91.4%. The algorithm has a high computing speed and high accuracy and can train data in batches. Therefore, it can be widely used in the field of online monitoring and evaluation of electrical equipment status.

Highlights

Introduction published maps and institutional affilThe insulating structure and operation conditions of converter transformers differ from those of conventional AC transformers
The valve-side winding of a converter transformer can withstand AC–DC combined voltage (ADCV) and harmonic voltage components
The international council on large electric systems (CIGRE) statistics report that the failure rate of converter transformers is about twice that of AC transformers and that considerable cases of insulation failure are caused by creepage discharge at the oil–paper interface [1,2,3]

Summary

Introduction

The insulating structure and operation conditions of converter transformers differ from those of conventional AC transformers. The valve-side winding of a converter transformer can withstand AC–DC combined voltage (ADCV) and harmonic voltage components. The international council on large electric systems (CIGRE) statistics report that the failure rate of converter transformers is about twice that of AC transformers and that considerable cases of insulation failure are caused by creepage discharge at the oil–paper interface [1,2,3]. The oil–paper interface remains the vulnerable part of a converter transformer insulation and has been studied widely. Studies have been conducted on the creepage discharge characteristics of oil–paper insulation under ADCV using partial discharge measurements and other methods, and beneficial results have been obtained [1,2,3]. The partial discharge phenomenon can reflect the insulation failure process

Methods

Results

Conclusion