1011-530
10
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 563 volts.
Formula Method – Example 2
An installation has the following profile:
•
Highest anticipated continuous system line-to-neutral voltage (
V
L-n
): 139.44 kV
•
Nameplate rating of the capacitor units (
V
r
): 19.92 kV
•
Number of series groups per phase (
S
): 7
•
Number of capacitor units in parallel per series group (
P
): 12
V
o
(volts)
3
10
20000
⋅
⋅
2 1
( )
3
2
⋅
(
)
10
1
–
(
)
+
-------------------------------------------------------
10714 volts
=
=
V
o
(per unit)
10714
9960
---------------
1.0757 per unit (or 7.57% overvoltage)
=
=
V
o
(volts)
3
10
20000
⋅
⋅
2 2
( )
3
2
⋅
(
)
10
2
–
(
)
+
-------------------------------------------------------
11538 volts
=
=
V
o
(per unit)
11538
9960
---------------
1.1585 per unit (or 15.85% overvoltage)
=
=
V
n
(volts)
1
( )
20000
⋅
2 1
( )
3
2
⋅
(
)
10
1
–
(
)
+
-------------------------------------------------------
357 volts
=
=
V
n
(volts)
2
( )
20000
⋅
2 2
( )
3
2
⋅
(
)
10
2
–
(
)
+
-------------------------------------------------------
769 volts
=
=
357 volts
769 volts
+
2
---------------------------------------------------
563 volts
=
Summary of Contents for BankGuard PLUS
Page 4: ...1011 530 4...
Page 6: ...1011 530 6 Figure 1 Vo versus F P Ungrounded Wye Capacitor Bank...
Page 50: ...1011 530 50...
