Environmental Engineering Reference
In-Depth Information
5
Power System Analysis
5.1 Introduction
The preceding chapters have discussed electrical generators in some detail. Attention will
now turn to the transmission and distribution systems that carry the generated power to the
loads. In addition to their obvious task of carrying electricity over a distance and allowing
generators and loads to be geographically separated, transmission and distribution systems
also serve to provide interconnection. The interconnection of loads provides valuable aggre-
gation and hence smoothing, as discussed in Chapter 3. Also, the parallel operation of genera-
tors allows ineffi cient part-loaded operation of individual generators to be largely avoided
(Chapter 7), and thus overall effi ciency is greatly increased. Furthermore, the parallel opera-
tion of generators and of sections within the transmission and distribution systems provides
redundancy, allowing the overall impact of any single component failure to be minimized.
Thus, even in situations where generators are located close to loads, the benefi ts of an inter-
connected power system should not be underestimated.
The effective operation of a power system requires that the routing of power from genera-
tors to consumers is carried out through the network so that transmission equipment is not
overloaded, losses in the network are kept to a suitably low level, voltages at various nodes
are maintained within limits and loss of generation or transmission equipment does not lead
to an unacceptably high frequency of blackouts. To ensure that power systems operate
securely and effi ciently, special computational techniques have been developed by utilities.
This chapter briefl y describes these techniques and illustrates their use in determining the
voltage at the nodes of the network, the complex power fl ows in transmission lines and the
currents during fault conditions. The effect on the network of adding renewable energy gen-
erators can be assessed using such techniques, as will be examined in Chapter 6.
5.2 The Transmission System
[1]
Figure 1.12 in Chapter 1 gave a pictorial view of a typical power system and the desirability
of using various voltage levels for transmission were explained. Overhead lines, supported
