Modern Power Transformer Practice

Frontmatter

1. General Information

Abstract

The types of transformers considered in the following chapters are commonly employed in the chain of electric power supply from generating stations to consumers of electric energy. They include some special transformers designed for particular industrial purposes.

R. Feinberg

2. Theory of Transformer Design Principles

Abstract

The general problem of design may be defined as that of determining the most suitable form of equipment, if both technical considerations and cost are taken into account. A satisfactory result is not obtained simply by the solution of a series of equations. The design process is basically iterative, whether performed by hand or by computer.

A. B. Crompton

3. The Use of the Automatic Electronic Digital Computer as an Aid to the Power Transformer Designer

Abstract

The automatic electronic digital computer is a device that can be programmed to perform automatically a sequence of arithmetic operations on numbers presented in digital form at very high speeds. The basic elements which constitute such a device are as follows.

K. Rowe

4. Transformer Cores

Abstract

The cores of today’s power transformers still retain the essential features developed over 80 years ago: they are built up from thin flat laminations of soft iron.

S. Palmer

5. Windings

Abstract

The design of any transformer winding must fulfil certain basic requirements. It must withstand the electric stresses imposed on it during test. These tests are intended to ensure that a transformer passing them will give trouble-free service for many years under the conditions it is likely to meet after its installation. They are therefore of three sorts: (1) a test at power frequency for about 1 min to prove its margin over its operating voltage, (2) a surge test and (3) a switching surge test—both (2) and (3) are to prove its ability to withstand voltage surges due to atmospheric disturbance and to switching.

H. W. Kerr

6. On-load Tap-changing Equipment

Abstract

On-load tap-changing equipment is required as a necessary accessory to a transformer normally employed in an electric power supply system (see chapters 10 and 12). By changing the tapping on a winding, the equipment provides the facility to vary the turns ratio of the transformer and thus the level of its output voltage.

B. C. Savage

7. Transformer Processing and Testing

Abstract

Testing is a very important stage in the manufacture of any product. Not only is the satisfactory outcome of the tests a guarantee to the customer that the equipment will meet the required specification, but it is also a confirmation to the design office of their calculations as well as providing them with valuable data for future designs.

H. Jackson, K. Ripley

8. Transformer Noise

Abstract

Transformers emit a distinctive hum which is continuous, of constant level and irrespective of load and which consists of discrete frequency components. Although over the years the noise produced by transformers of given rated power has been reduced, the problem has become severe owing to the increasing size and number of transformers and the tendency for these to be located closer to load centres. The result has been that the likelihood of annoyance to residents has become potentially greater and that more and more precautions now need to be taken at the planning stage. Complaints can to a large extent be forestalled provided suitable estimates are made at this stage and provided measures are taken to limit the noise.

J. Dunsbee, M. Milner

9. Distribution Transformers

Abstract

While there is no generally recognised definition, a distribution transformer may be defined as a transformer used to supply power, for general purposes, at final distribution voltage level from a higher-voltage distribution system. The minimum rating is usually regarded as 5 kVA, but the maximum is somewhat indefinite. For public supply purposes it is not common to use rating exceeding 1000 kVA, but industrial sub-stations frequently have higher ratings. 3 MVA is normally the practical limit for loading at medium voltage, as the impedance necessary to limit fault current to the usual switchgear ratings rises to impractical percentages at higher ratings.

H. K. Homfray, D. Boyle

10. Power System Transformers and Inductors

Abstract

Modern power supply networks are usually very complex, with many generating stations, often a variety of transmission voltages and a large number of interconnection and distribution points. Quantities of energy transmitted are large, and short-circuit fault levels are high.

R. Feinberg, R. J. Gresley

11. Special Transformers

Abstract

In supplying electric power to large office blocks and flats, the supply authority would naturally prefer to install the distribution transformer in the building itself, so as to reduce the length of low-voltage cable runs, which would result in lower costs and fewer problems with voltage regulation. The consequence of fire in multi-storey buildings becomes more and more serious as the population density of the building increases. The installation of an oil-filled transformer in the building is held to increase the fire risk.

T. Kelsall

12. Transformers in Distribution Systems

Abstract

The customer’s specification (see section 3.2) meets constraints set by the supply system, the load to be supplied, the environmental aspects and the need to provide a reasonably secure supply by the most economic means.

L. Lawson

Backmatter