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Regulator
Feeder

Load 1 Load 2 Load 3
substation
Dotted line is high load period.
1.04 Solid line is light load period.
Voltage (pu) 1.00
1.02
0.98
0.96
0.94
Distance from substation
Figure 7.3 - Illustration of feeder load variation

4. Metering: Most substations do have some sort of metering
device that records, at a minimum, existing current and current
max and min that have occurred in the last time period (e.g., 1
hour). Digital recording is also heavily used and capable of
recording a large amount of substation operational information.

Most distribution substations carry between 5 and 60 MVA.

4 Make a written translation of the following:
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 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

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