4

Distribution

And God said, “Let there be light” and there was light, but the Electricity Board said He would have to wait until Thursday to be connected.

—Spike Milligan

4.1 Introduction

This chapter is about the next step in the classical power grid toward reaching the consumer after the transmission system. The transmission system delivers large amounts of power at high voltage and low current over long distances to population centers where power is required. The next step in the pre-smart-grid system is to distribute the power to consumers, either residential or industrial. From a high level this involves two key steps: transforming the power to lower voltage and distributing or fanning the power out to individual consumers.

Referring back to Table 3.1, the communication involved could approximate a MAN. The transmission system ends at a substation, which distributes power through feeders to populated areas. This chapter begins by discussing transformers in the distribution system, feeders, a quick discussion of power line, and distribution system topologies. Because the distribution system reaches out to the consumer, this part of the grid most exposes the power system to the public. This raises safety concerns and requires that power protection receives a high priority. The next part of the chapter focuses upon power protection mechanisms. While many of these mechanisms can be configured to operate based upon local information, some protection techniques have relied upon ...

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