A transformer is usually considered to be a non-mechanical apparatus for changing the voltage of an alternating current (AC) supply. Transformers are built in a very wide range of sizes from small devices used inside consumer products to very large devices used to connect generators to the national transmission network. This chapter will focus on medium and large transformers. In this context these are considered to be any transformers which are so large or else so complex as not to be manufactured in bulk. This generally includes all transformers rated at more than 2,500 kVA and all transformers which do not include a winding intended for connection to the low-voltage distribution network, but practice varies between countries and between users.

Chapter Contents:

• 14.1 Introduction
• 14.2 Specification of user requirements
• 14.2.1 Need for user specifications
• 14.2.2 Functional and design specifications
• 14.2.3 Specifications and standards
• 14.2.4 Specification content
• 14.2.5 Guidance on specifications
• 14.3 Supplier selection
• 14.3.1 Industry changes
• 14.3.2 Timing
• 14.3.3 Format
• 14.3.4 Aims
• 14.3.5 Main elements of process
• 14.4 Testing
• 14.4.1 Classification of tests
• 14.4.2 Performance tests
• 14.4.3 Thermal tests
• 14.4.4 Dielectric tests
• 14.4.5 Short-circuit withstand
• 14.4.6 Condition assessment testing
• 14.5 Operation and maintenance
• 14.5.1 Limitations on transformer life
• 14.5.2 Preventive and corrective maintenance
• 14.5.3 Time- and condition-based maintenance
• 14.5.4 Oil tests
• 14.5.5 Electrical tests
• 14.6 Concluding remarks
• Bibliography

Inspec keywords: distribution networks; power transformers

Other keywords: generator connection; consumer product; nonmechanical apparatus; national transmission network; AC supply; alternating current supply; low-voltage distribution network; winding; transformer

Subjects: Transformers and reactors; Distribution networks