Assessment of best practices for mitigation of rapid voltage change due to transformer inrush

Abstract

The penetration of Distributed Energy Resources (DERs) on the power system has come with its own set of problems, especially in the power quality domain. As DERs continue to be integrated at the transmission and sub-transmission voltage level, power quality engineers are faced with the unique situation of having to regulate a source of generation rather than a load. One of the important outcomes of such integration has been the concern about increase in cases of rapid voltage change (RVC). While there is evidence to indicate that DERs themselves do not contribute much to voltage fluctuations in the power grid, there have been recorded instances where the energization of transformers used to integrate DERs to the grid has led to an RVC event. This paper presents the current status of research on RVCs, particularly in terms of regulation, and then outlines the various methods and strategies that can be used to counter the problem of RVC that results from energization of transformers on the utility grid. A case study from an RVC event caused by transformer energization is presented and then used as a baseline, to study the effect of various mitigation techniques, using EMTP simulations. Various techniques have been contrasted and compared in terms of cost and effectiveness. The paper finally closes with a discussion of the future avenues and expected work with regards to Power Quality in this field.