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Figure 7.2 - A lower-reliability design

3. Voltage regulation: Because current I flows from source to
load along the length of the feeder, and because the feeder has
some amount of impedance per unit (pu) length Z, the feeder
will cause a voltage drop IZ volts per unit length. Thus, loads
connected along the length of the feeder will see different
voltage levels with the load at the far-end of the feeder seeing
the lowest voltage of all. This is illustrated by the solid line in
Figure 7.3. Note that this line indicates the voltage at the
substation end of the feeder is 1.02pu. However, the voltage at
feeder far-end is about 0.97pu (residential customers would be
seeing about 116 volts instead of 120). If the load were to
increase, the far-end voltage would drop to an even lower
value. As a result, we must regulate the voltage along the
feeder as the load varies. Ways to do this include substation
load tap-changing transformers (LTCs), substation feeder or
bus voltage regulators (employed in Figure 7.3), line voltage
regulators, and fixed or switched shunt capacitors.

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