UFC 3 -520-01
June 10, 2002
Table C -2. Common Capacitor Reactive Power Ratings
Voltage Rating
Number of
kVAR Rating
BIL kV
(rms)
Phases
216
5, 7.5, 131/3, 20, and 25
1 or 3
30
240
2.5, 5, 7.5,10, 25, 20, 25, and 50
1 or 3
30
480
5, 10, 15, 20 25, 35, 50, 60, and 100
1 or 3
30
600
5, 10, 15, 20 25, 35, 50, 60, and 100
1 or 3
30
2,400
50, 100, 150, and 200
1
75
2,770
50, 100, 150, and 200
1
75
4,160
50, 100, 150, and 200
1
75
7,200
50, 100, 150, 200, 300, and 400
1
95
12,470
50, 100, 150, 200, 300, and 400
1
95
13,800
50, 100, 150, 200, 300, and 400
1
95 and 125
Refer to IEEE 18 for ratings at other voltages.
C-3.2
The calculated capacitor size will rarely exactly match one of the available
sizes. The decision of whether to select the next larger or the next smaller size
depends on the circuit configuration and the desired power factor. Paragraph C -4
provides specific design criteria regarding capacitor size.
C-3.3
IEEE 18 establishes the required design tolerances for capacitors.
C-4
Design Criteria .
C-4.1
Consider requiring power factor correction as part of the facility design.
Power factor correction has to be justifiable based upon operational performance
improvements or cost-savings, including any potential effects caused by interaction with
other devices.
C-4.2
If used, apply capacitors to obtain a power factor range of 0.85 to 0.95. A
power factor of 0.85 will satisfy most operational requirements, but the actual minimum
value should also be based on any revenue metering penalties established by the local
commercial utility for low power factors. Little, if any, economic ad vantage will usually
be realized if attempting to correct above a power factor of 0.95. Ensure that power
factor correction will not cause a leading power factor under no -load conditions.
C-4.3
Power factor correction requires particular attention if nonlinear loads are a
significant portion of the facility load; this includes electronic equipment, ASDs, UPS
systems, and other significant sources of harmonic distortion. Capacitors can resonate
with nonlinear loads and cause additional distortion of the e lectrical system voltage and
current. In this case, the capacitor(s) might not improve the power factor at all. Also,
resonant conditions can cause capacitor failure. If facilities contain a significant
proportion of nonlinear loads, evaluate the application of a synchronous condenser
instead. Synchronous condensers are often applied at the service entrance, which
might not solve all power factor problems throughout the facility.
C-5
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