MIL-HDBK-1004/5
3.2.3.1
Field Adjustment. Adjust the nominal indicated rating of the shunt
reactor to suit the actual capacitance of the cable provided. Make field
measurement of the actual capacitance after the cable is installed, and the
correct shunt reactor tap can be chosen to the closest unity power factor
setting.
3.2.3.2
Nominal Rating Sizing. An example of nominal shunt reactor sizing
follows. If the nominal rating calculated is less than 10 kvar for a feeder,
the shunt reactor may not be necessary to decrease voltage drop. However, its
installation provides for capacitive discharge which increases operator
safety.
System voltage (V.S-) = 4,160 volts
Feeder Length = 1 mile
Maximum capacitance allowed = 0.603 microfarads per mile
V.S- squared
=
(4,160) squared
= 26.2
Nominal rating =
1,000X.C-
1,000 (660)
Required nominal rating = 26.2 kvars
3.3
Central Plant Design. A central plant is the point where the
station's medium-voltage distribution system 60-Hz (in rare cases 50-Hz) input
is converted to 400-Hz power for distribution by a 400-Hz feeder distribution
center to the station's medium-voltage distribution system. A typical 400-Hz
central plant is shown on Figure 3. Normally, the plant will be an unmanned
facility.
3.3.1
Reliability. The continuous operation of the central 400-Hz
medium-voltage system is extremely critical. Standby components are required
at the central plant to ensure no major loss of 400-Hz electric power.
3.3.2
System 60-Hertz Input Power. The design of the 60-Hz input system
is covered in this handbook only to the extent of providing necessary 400-Hz
system reliability. For this reliability, two primary inputs from different
feeders or electric sources of 60-Hz electric power are required at the
central plant.
Primary Feeder Source. Generally, provide a prime and an alternate
3.3.2.1
feeder from the installation's 60-Hz primary (medium-voltage) distribution
system. An area having a 400-Hz load large enough to require a central
medium-voltage system is an area with a load density which is both large and
sufficiently important enough to require more than one 60-Hz primary
distribution feeder.
3.3.2.2
Diesel-Engine Generator Source. Provide an emergency diesel-engine
generator system (see MIL-HDBK-1004/4, Electrical Utilization Systems) as the
alternative source where provision for an alternative feeder is more costly
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