• Book Name: Protection of Industrial Power Systems
• Author: T. Davies
• Pages: 245
• Size: 20 MB

Protection of Industrial Power Systems Pdf

The protection which is installed on an industrial power system is likely to be subjected to more difficult conditions than the protection on any other kind of power system. The fault level may be variable and in some cases very limited; the supply arrangements can be altered by switching in or out interconnections between substations; the starting current of large motors may represent a significant proportion of the load current and so on.

In addition industrial power systems are often changed to accommodate additional plant with equipment installed by different contractors and although protection is provided the overall co-ordination of the scheme may be unsatisfactory.

Protection of Industrial Power Systems Pdf

This book is intended to help the Works Electrical Engineer and the Contractors’ Engineer to achieve an understanding of the subject of protection. The whole area of industrial power system protection is covered starting with the many simple devices which are used. These are usually based on the discrimination by time principle and a number are described. In addition the capabilities of the modern cartridge fuse are examined.

The more conventional types of relays which are used have more accurate operating characteristics. These are achieved by particular application of the basic relay elements so as to interpret the power system parameters.

The link between the power system and the relay is the current
transformer and all aspects of its construction, design and operation are discussed in order that this important component can be fully understood.

Although it is not possible to divorce mathematics from fault calculations the method is simplified to the extent that little more than a knowledge of Ohm’s law is required to tackle the three-phase and earth-fault calculations for any system.

The most widely used relay in any industrial power system is the inverse definite-minimum time overcurrent relay. Its application is critically examined so that optimum plug and time settings can be determined to provide a fully discriminative scheme.

The theory of the Merz-Price protection system from which most discrimination by comparison schemes are derived, the limitations which necessitate the modification to the Merz-Price system and the development of the high-impedance relay are discussed in detail. The application of the high-impedance relay to provide stability during through-faults and sensitivity to internal faults is demonstrated.

The application of relays to busbar protection schemes and all aspects of the protection of transformers, feeders and electrical machines are dealt with and the control circuits which are associated with protection. There is a comprehensive description of the tests required following installation and those that are required during a maintenance programme. Finally the care of protection relays is covered.

In writing this book the words and experience of many people have been used, a lot of information and advice has been gratefully accepted.

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