Electric Power Principles by James L. Kirtley;

Author:James L. Kirtley; [Неизв.]
Language: eng
Format: epub
ISBN: 9781119585237
Publisher: John Wiley & Sons, Inc.
Published: 2020-03-09T00:00:00+00:00

10.3.4 Example of Fault Calculations

In this example, the objective is to determine maximum current through the breaker B due to a fault at the location shown in Figure 10.19. All three types of unbalanced fault, as well as the balanced fault, are to be considered. This is the sort of calculation that has to be done whenever a line is installed or modified so that protective relaying can be set properly. (Note that the transformer connections might be different in any particular power system.) The fence‐like symbols at either end of the figure represent infinite buses, or positive sequence voltage sources.

The parameters of the system are given in Table 10.1.

The first step in the fault calculation is to find the sequence networks. These are shown in Figure 10.20. Note that they are exactly like what one would expect to have drawn for equivalent single‐phase networks. Only the positive sequence network has sources because the infinite bus supplies only positive sequence voltage. The zero sequence network is open at the right‐hand side because of the delta–wye transformer connection there.

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