Performance Comparison of PD Data Acquisition Techniques for Condition Monitoring of Medium Voltage Cables

Already installed cables are aging and the cable network is growing rapidly. Improved condition monitoring methods are required for greater visibility of insulation defects in the cable networks. One of the critical challenges for continuous monitoring is the large amount of partial discharge (PD) data that poses constraints on the diagnostic capabilities. This paper presents the performance comparison of two data acquisition techniques based on phase resolved partial discharge (PRPD) and pulse acquisition (PA). The major contribution of this work is to provide an in-depth understanding of these techniques considering the perspective of randomness of the PD mechanism and improvements in the reliability of diagnostics. Experimental study is performed on the medium voltage (MV) cables in the laboratory environment. It has been observed that PRPD based acquisition not only requires a significantly larger amount of data but is also susceptible to losing the important information especially when multiple PD sources are being investigated. On the other hand, the PA technique presents improved performance for PD diagnosis. Furthermore, the use of the PA technique enables the efficient practical implementation of the continuous PD monitoring by reducing the amount of data that is acquired by extracting useful signals and discarding the silent data intervals.© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Identification and Location of PD Defects in Medium voltage Underground Power Cables Using High Frequency Current Transformer

Fault location is an important diagnostic task in condition monitoring of underground medium voltage cables. Available solutions are well capable of determining the location of a single partial discharge (PD) defect on a cable section. In case several PD defects are active simultaneously along a cable section, the interpretation of the measured data becomes complex to identify the presence of more than one PD sources. In this paper, experimental investigation of two PD defects/sources at different locations on a medium voltage (MV) cable section is presented. A high frequency current transformer is used for single end PD measurements. Time domain reflectometry-based in-depth study of the reflected pulses provides the most valuable information to identify the presence of PD sources which further leads to the location of the individual PD sources. In this paper, the proposed solution is presented for two PD sources, however, the same methodology can be extended to locate multiple PD sources on the cable.fi=vertaisarvioitu|en=peerReviewed

Characterization of Corona and Internal Partial Discharge under Increasing Electrical Stress using Time Domain Analysis

Aging and abnormal stresses accelerate insulation degradation and reduce the lifetime of power equipment. Partial discharge (PD) measurement is an effective tool to study the condition of the insulation. Reliability of PD diagnosis depends on the accurate interpretation of the measured PD signals. PD itself is a complex phenomenon and the presence of different types of discharge sources makes interpretation of the PD data quite challenging. This paper investigates internal and corona PDs in order to distinguish them when both are active simultaneously. The presented work identifies the PD sources based on time domain analysis that provides a simplified solution as compared to identification techniques based on different statistical features leading to complex data processing. While superimposed phase-resolved partial discharge (PRPD) patterns provided incomplete information, time domain PD characteristics e.g. pulse repetition rate and pulse amplitude combined with PRPD mapping are analyzed to differentiate PD activity. Furthermore, the electrical stress (voltage level) is increased gradually in the experiments made and PD behavior is studied. The presented technique contributes to enhancing the accuracy of PD diagnosis that is necessary for appropriate decision making concerning the repair of affected components.© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.fi=vertaisarvioitu|en=peerReviewed