Transformer Monitoring and Protection in Dynamic Power Systems – A Review

Boqi Xie,Dongbo Zhao,Tianqi Hong

doi:10.3389/fenrg.2020.00150

Abstract

Increasing distributed energy resources, especially the renewable energy resources (RESs) are being installed across power systems these years. These RESs, including solar photovoltaic, wind turbines, etc., provide opportunities for operators to improve power quality, enhance power system resilience, and help meet green energy goals. However, RESs also bring challenges to the operators. As the operating conditions of RESs vary drastically, power systems may experience larger dynamics compared with the traditional power systems with limited RESs. Such dynamics may impose some impacts on devices in power systems. Transformer, as one of the critical and expensive components in power systems, is in need to be protected and monitored constantly. With this said, monitoring and protection of transformers is significant and critical in power system industry as well as in academic research. This paper presents a comprehensive review of the existing transformer monitoring and protection methods. The paper first introduces monitoring and protection approaches for the legacy low frequency transformers, as those transformers are still playing a major role between low frequency interfaces. Then, the literature of the protection of solid-state transformers, i.e., power electronics-based transformers, is investigated. A summary of the present technology of transformer monitoring and protection follows.

Highlights

Distribution systems are transforming from passive systems to active ones as an increasing number of distributed energy resources (DERs), especially renewable energy resources (RESs) are being installed
This paper presents a comprehensive review of the existing transformer monitoring and protection methods
Note that if the measuring circuit is connected to the capacitive-graded bushing as shown in Figure 3, the capacitance C1 may substitute the coupling capacitor in the coupling unit

Summary

INTRODUCTION

Distribution systems are transforming from passive systems to active ones as an increasing number of distributed energy resources (DERs), especially renewable energy resources (RESs) are being installed. Short-circuit impedance method and transfer function method (similar as frequency response analysis) are the two major on-line methods for winding deformation monitoring. On-Line Partial Discharge Testing Partial discharge generates low-amplitude (in the milliampere range), short-duration (in microsecond range or even below) current pulses (IEEE, 2013a) Based on these two characteristics, two commonly used partial discharge detection methods are developed: (1) Detection of acoustic signals, and (2) Measuring electrical quantities generated from partial discharge (Wang et al, 2002). According to IEEE (2010), three major circuit components are required: (1) Coupling unit, which captures the partial discharge signals from the terminals of the monitored transformer, (2) measuring instrument, which processes the captured partial discharge signals and evaluates the apparent charge level, and (3) associated high-voltage and low-voltage leads and measuring cables. Note that if the measuring circuit is connected to the capacitive-graded bushing as shown in Figure 3, the capacitance C1 (shown in Figure 3) may substitute the coupling capacitor in the coupling unit (i.e., no coupling capacitor is required in the coupling unit)

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Communication Method