Power transformers – design and manufacture

by S Mtetwa, Eskom


Published in: Transformers and Substations Handbook: 2014

Chapter 1: Design and manufacture of transformers - page 12

Enquiries: Email MtetwaNS@eskom.co.za


Read the full article on Power transformers - design and manufacture in PDF format.


The power transformer has always been a major and expensive component in the power system. In growing economies and, electrification projects around the world, power transformers are in demand and their prices continue to increase, with the lead times to source them following the same pattern. It is always desired that a return on investment be realised on power transformers because they require a significant capital investment. In many cases, power transformers fail before they reach their expected life span.

Studies show that most power transformer failures occur around midlife [appraisal] with the known leading causes of the power transformer failures being windings, tap changers and bushings in decreasing order. The main question then is: What is being done, or can be done, in the design phase of a power transformer in order to achieve the expected lifespan and how are the leading causes of power transformer failures being addressed?

Power transformer owners need to face the reality that a power transformer life management practice that will enable the utility to safely, economically, and with a high degree of reliability and availability, utilise its power transformers for their entire, expected life span, does not start when the power transformer lands on the intended site. The stages prior to the delivery of a power transformer are critical and they require serious attention.

The life cycle of a power transformer can be summarised as:

o Identification
o Specification
o Design
o Design review
o Manufacture
o Test
o Transport
o Install
o Commission
o Operate
o Maintain
o Retire or dispose of


From this, one can see that prior to switching for operation there have been many life cycle stages in making a power transformer that will last a certain period, from between a few milliseconds to a number of years.


Take note

  • The power transformer is a critical component of a power system.
  • There are several stages prior to delivery of a power transformer.
  • The first stage is to identify exactly the type power transformer that is required.