Column: Transformer maintenance

Column: Transformer maintenance

Vol. 5 Issue 2

Beneficial investment for transformer maintenance


Transformer is the most important and pricey piece of equipment in the transmission system, so an adequate maintenance strategy is required to ensure uninterrupted electricity supply, preserve transformer life and minimize the investment. The crucial phases to ensure reliable and economical exploitation of a transformer within any maintenance strategy are inspection and audit of the manufacturing process, and adequate preparation before it is energized. Dissolved gas analysis (DGA) applied periodically is the most cost-effective test for transformers. However, excessive maintenance, tests or treatment can cause more damage to the insulating materials than prevent the potential failure. A specific maintenance policy is driven by economic aspects, consequences of power outage, insurance companies, and the knowledge and beliefs of the transformer owner. Despite proper maintenance, a small percentage of transformers will inevitably fail.

1. Introduction

Transformers and oil-filled equipment are one of the most important and vital rings in the electricity supply chain, allowing efficient and inexpensive transport of energy. The transformer technology is about 120 years old and has not changed much since the 19th century. The transformers have remained reliable and mostly free of special or sophisticated maintenance for all these years, although the power and voltage increase and ratio of MVA to insulation weight decrease significantly. Most of manufacturers and planners create sophisticated, quality products tailored to very tight specifications. However, although transformer failures are rare, when they happen, they are often quite spectacular. Besides the bad publicity when such a failure occurs, it is also not easy to find a spare unit for this most important and pricey piece of equipment in the transmission system.

It is often a case that the transformer owner has to select the most adequate strategy to ensure uninterrupted electricity supply, to preserve transformer life and, at same time, to invest as less as possible. Sometimes the cost of the tests and maintenance can be higher than the price of the equipment itself.

Any misunderstanding or compromises in the maintenance policy will lead to either unrevealed failure or unnecessary and expensive maintenance. The advantages of each maintenance philosophy will be explained from the user point of view.

Most transformers do not fail because of the degradation process of oil and/or paper, not even in the presence of moderate content of moisture.