A Study of the Root Causes of High Failure Rate of Distribution Transformer - A Case Study

Abstract

A distribution transformer is one of major electrical equipment that links the power utility and power consumers. It is what enables the power utility to supply electricity to consumers. In recent time, there has been an upsurge of distribution transformers premature failure before reaching the desired and designed service life. Consequently, the power utility has been incurring huge economical losses in replacing the faulty transformers or repairing them. On the other hand, failure of transformer inconveniencies power end users by interrupting the power supplies for prolonged period of time before the faulty transformer is replaced. In this paper, an effort is made to investigate the root causes of premature failure of distribution transformers. Research has revealed that line surges and switching transients are among the main causes of the transformers failures as this accelerates deterioration of insulation materials. This has been aggravated by lack of lightning arrestors and vandalism of low voltage and high voltage earthing systems. It is also noted that a transformer is usually 'killed' by unusual stresses that usually break down its weak insulation and hence leading to reduced transformer life. Use of concrete poles with earth wire appended is proposed to deter vandalism of earthing wire. In addition, proper fuse grading, installation of High Voltage (HV) expulsion fuses and regular Operational and Maintenance (O&M) has been recommended to reduce the premature failure of distribution transformers.