S&C BankGuard PLUS, Setup Instructions

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7 1011-530
Figure 2.
V
n
versus
F/P
(Ungrounded Wye Capacitor Bank)
Graphical Method – Example 1
An installation has the following profile:
•
Highest anticipated continuous system line-to-neutral voltage ( V
L-n
): 20 kV
•
Nameplate rating of the capacitor units ( V
r
): 9.96 kV
•
Number of series groups per phase ( S ): 2
•
Number of capacitor units in parallel per series group ( P ): 10
For F = 1, enter at 10 on the horizontal scale (1/10 = 10% of capacitor units isolated
from a series group). Follow this up to the curve for
S
= 2 (2 series groups per phase).
Here on the vertical scale, V
o
= 1.072 per unit.
Similarly, for F = 2, enter the graph at 20 on the horizontal scale (2/10 = 20% of capaci-
tor units isolated from the same series group). Follow this up to the curve for
S
= 2.
Here, V
o
= 1.16 per unit. Because we are looking for a V
o
of 1.1 or less per unit, our F
c
in
this example is 2.
With
V
L-n
= 20 kV and 2 series groups per phase, the capacitor units are normally oper-
ated at 10 kV. Therefore: