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Chapter 10

Single-phase and

Three-phase

Distribution Systems

When electrical power is distributed to its point of utilization, it is
normally either in the form of single-phase or ee-phase thr alternating cur-
rent (AC) voltage. Single-phase AC voltage is distributed into residences
and smaller commercial buildings. Normally, three-phase AC voltage is
distributed to industries and larger commercial buildings. Thus, the main
types of power distribution systems are residential (single-phase) and in-
dustrial or commercial (three-phase).
An important aspect of both single-phase and three-phase distribu-
tion systems is grounding. Two grounding methods, system grounding and
equipment grounding, will be discussed in this chapter, along with ground-
fault protective equipment.

IMPORTANT TERMS

In Chapter 10, single-phase and three-phase power distribution sys-
tems are discussed. After studying this chapter, you should have an un-
derstanding of the following terms:

Residential Distribution
Commercial Distribution
Industrial Distribution
Single-Phase, Two-Wire Distribution System
Single-Phase, Three-Wire Distribution System
Hot Line
Neutral
System Ground
Equipment Ground