BOOK_CONTENT
From Protection of Electricity Distribution Networks, 2nd Edition

Previous chapters have detailed the make up and operating characteristics of various types of protection relays. This chapter considers the combination of relays required to protect various items of power system equipment, plus a brief reference to the diagrams that are part of substation design work. A general knowledge of these diagrams is important in understanding the background to relay applications.

12.1 Protection Schemes

It is difficult to define precisely the protection schemes that should be adopted for an electricity distribution system, given the large number of valid alternatives for each situation, but some schemes will be presented as a guide for protecting the various elements that make up a power system. However, any protection scheme should strike a balance between the technical and economic aspects so that, for example, sophisticated protection devices are not used for small machines or for less important power system elements.

12.1.1 Generator Protection

Generator protection should take into account the importance of the generator and its technical characteristics such as power, voltage and earthing arrangement, plus any economic considerations. A complex protection scheme can ensure that the generator is protected against whatever faults may occur. However, it is unlikely that such a cost could be justified for every generating station, especially those with small units. It is, therefore, necessary to define a protection scheme that is adequate for the size of the machine.

Two generator protection schemes are given below, based on suggestions by manufacturing companies.

Small Generators

For small generators, typically up to...

Copyright The Institution of Electrical Engineers 2004 under license agreement with Books24x7

Products & Services
Signal Generators
Signal generators and waveform generators are used to test and align all types of transmitters and receivers, to measure frequency and to generate a signal, waveform or noise source. Signal generators can use AC energy, audio frequency (AF) and radio frequency (RF) to function.
Venturi Vacuum Generators
Venturi vacuum generators use the flow of motive fluid such as air, steam, or liquid to evacuate air.
Power Supplies
Power supplies are electrical devices that deliver electric power to one or several loads. They generate the output power by converting an input signal into an output signal.
IC Signal Generators
IC waveform generators provide several different waveforms or functions at the desired frequency.

Topics of Interest

13.1 General The various protection schemes described in earlier chapters in this book are provided to disconnect faults on power systems promptly, with the minimum of disruption to the network and...

2.1 INTRODUCTION This chapter describes different types of electrical diagrams. It explains how the diagrams are developed from original concepts into drawings which describe the full operation of...

9.4 The New Era in Protection - Microprocessor vs Electronic vs Traditional 9.4.1 Background Electromechanical relays of various types have been available from the earliest days of electrical power...

13.1 Protective Relay Systems The basic function of protection is to detect faults and to clear them as soon as possible. It is also important that in the process the minimum amount of equipment...

INTRODUCTION Figure 25.1 illustrates the overall protection scheme in a generating station. The auxiliary equipment inside the plant requires 5 to 10 percent of the power generated. The remainder...