Impact of Battery Energy Storage System on Distribution Transformer Insulation Life

Abstract

Distribution transformer (DT) face extreme duty cycles due to improper management of electrical network. The life of a transformer is largely determined from the insulation's strength. Overloading is observed to be one of the major causes for insulating material deterioration since it creates thermal stress in the windings and the core. Battery Energy Storage System (BESS) units are a promising solution to manage the overloading of DT. The placement of a BESS at the secondary terminals of a DT with appropriate charge & discharge control algorithm can manage the DT loading. In the proposed methodology, the charge and discharge condition for BESS operation is pre-defined (day-ahead) based on a neural-network based predictive algorithm so as to minimize the loss-of-life (LoL) of the DT. Accordingly, a discharge and charge shave level for BESS operation was defined for a particular day by finding the respective operational thresholds from the load curve. This paper estimates the impact of BESS on operational life of a particular distribution transformer operational in the service area of a distribution utility in Delhi, India. The total LoL of the DT was calculated with and without BESS operation for the predicted load pattern. The network comprising of DT, dynamic load model and BESS was modeled in the Simscape software of MATLAB. It was observed from the results that BESS significantly reduces the insulation's LoL and thus extends the service life of a DT.