S&C BankGuard PLUS, Инструкции по установке

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11 1011-530
For F = 1,
For F = 2,
Because we are looking for a V
o
of 1.1 or less per unit, our F
c
in this example is 2.
Now calculate V
n
:
For F = 1,
For F = 2,
To determine the lockout level, calculate the midpoint value between V
n
for F = 1 and V
n
for F
= 2 (= F
c
):
Thus, the desired lockout level for this capacitor bank is 951 volts.
Gross
Overvoltage
You can calculate the capacitor bank neutral-to-ground voltage ( V
n
) resulting from a
fault within the capacitor bank that would short out an entire series group:
The desired gross overvoltage lockout level is the midpoint between the V
n
for the crit-
ical step and the V
n
resulting from shorting out a series group.
For Example 1 above, the V
n
for the critical step ( F
c
= 2) was 769 volts. The V
n
result-
ing from shorting out a series group is:
V
o
(volts)
3 12 139440
⋅ ⋅
2 1
( )
3 7
⋅ ( )
12 1 –
( )
+
-------------------------------------------------------
21544 volts
= =
V
o
(per unit)
21544
19920
--------------- 1.0815 per unit (or 8.15% overvoltage) = =
V
o
(volts)
3 12 139440
⋅ ⋅
2 2
( )
3 7
⋅ ( )
12 2 –
( )
+
-------------------------------------------------------
23457 volts
= =
V
o
(per unit)
23457
19920
--------------- 1.1776 per unit (or 17.76% overvoltage) = =
V
n
(volts)
1
( )
139440
⋅
2 1
( )
3 7
⋅ ( )
12 1
–
( )
+
------------------------------------------------------- 598 volts = =
V
n
(volts)
2
( )
139440
⋅
2 2
( )
3 7
⋅ ( )
12 2 –
( )
+
------------------------------------------------------- 1303 volts = =
598 volts 1303 volts +
2
------------------------------------------------------ 951 volts =
V
n
1
3 S 2 –
---------------
V
L n –
=
V
n
1
3 2
( )
2 –
--------------------
20000 volts 5000 volts = =