DC bias impact analysis on the capability of power transformer and failure risks

Abstract

A significant transition towards low-carbon, renewable energy sources and technological adaptation is mandatory in the present scenario to address climate change and achieve a sustainable energy system. Aligned with the upgradation in technology, as the need for efficient and smart energy grows, power electronics are being extensively used in power systems. Various factors can affect the pervasive use of power electronics associated with power transformers, thereby introducing the DC bias in the system. DC bias in the transformer leads to a shift in operating point, a rise in excitation current and a generation of harmonics. This causes an increase in core losses and temperature, resulting in exceeding the thermal limits and leading to transformer failure. Consequently, there is an emergency need to understand the DC bias capability of power transformers that aims at optimal transformer selection without being overrated. This research employs Ansys maxwell software to model and simulate a 500 kVA, 11kV/420V three-phase power transformer. The experimental investigation is carried out through a scale-down value of a 5 kVA laboratory prototype. The research findings revealed a significant negative impact of DC bias on power transformer capabilities that could be detrimental to its performance, health and lifespan. The analysis results provide valuable insights for the design engineer during the initial stages of designing a high-performance, cost-effective transformer with a low failure rate.