256 Electrical Power Systems Technology
Insulation Color Identification
Three-phase Delta-Delta Transformer Connection
Three-phase Delta-Wye Transformer Connection
Three-phase Wye-Wye Transformer Connection
Three-phase Wye-Delta Transformer Connection
Three-phase Open Delta Transformer Connection
Three-phase, Three-Wire Distribution System
Three-phase, Three-Wire, with Neutral Distribution System
Three-phase, Four-Wire Distribution System
“Wild” Phase
Grounding Electrode
Ground Fault Interrupter (GFI)
Hand-to-Hand Body Resistance
National Electrical Code (NEC)
Electrical Inspection
Voltage Drop of a Branch Circuit
Branch Circuit
Grounding Conductor
Nonmetallic-Sheathed Cable (NMC)
Metal-Clad Cable
Rigid Conduit
Electrical Metallic Tubing (EMT)
SINGLE-PHASE SYSTEMS
Most electrical power, when produced at the power plants, is pro-
duced as three-phase AC voltage. Electrical power is also transmitted in the
form of three-phase voltage over long-distance power-transmission lines.
At its destination, three-phase voltage can be changed into three separate
single-phase voltages for distribution into the residential areas.
Although single-phase systems are used mainly for residential power
distribution systems, there are some industrial and commercial applica-
tions of single-phase systems. Single-phase power distribution usually
originates from three-phase power lines, so electrical power systems are
capable of supplying both three-phase and single-phase loads from the
same power lines. Figure 10-1 shows a typical power distribution system-
from the power station (source) to the various single-phase and three-phase
loads that are connected to the system.