S&C BankGuard PLUS, Setup Instructions

Page: 47 / 50

47 1011-530
Calculated
Lockout Level
Verify the Calculated Lockout Level (capacitor banks only)
1. Check that no capacitor units have been isolated from the bank.
2. De-energize the capacitor bank.
Open the capacitor bank switching device. Then ground the bank, observing estab-
lished operating procedures and safety precautions.
3. Isolate the number of capacitor units calculated to lock out the bank.
To isolate the number of capacitor units (all in the same series group) previously calcu-
lated to lock out the bank, remove their respective fuses.
For grounded wye-connected banks where the number of series groups per phase is
odd,
you will not have to isolate as many capacitor units in a series group located
between the tap point and ground as in a series group located between the tap point
and the line.
4. Remove the temporary grounds, re-energize the bank, and record the
voltage.
If the voltage is greater than the lockout level, an automatic switching operation will
occur once the “Lockout Time Delay” ends and the
LOCKOUT INDICATOR LED will
turn ON.
As soon as you read the voltage, open the capacitor bank switching device to avoid
shortening the life of the capacitor units. Verify that no other capacitor units have been
isolated.
NOTE: After automatic lockout of the capacitor bank, you must press the LOCKOUT
INDICATOR button to return the bank to service. This permits closing of the capacitor
bank switching device.
5. De-energize and ground the capacitor bank, then reconnect the fuses.
Observe established operating procedures and safety precautions to de-energize and
ground the capacitor bank. Reconnect the fuses you previously removed to isolate the
capacitor units.
6. Repeat Step 1 through Step 5 for each remaining phase leg of the
capacitor bank.
7. For ungrounded wye capacitor banks, compare the calculated lockout
level and the measured voltages.
Check that the calculated lockout level is lower than the lowest voltage just measured.
If the calculated level is higher than one or two of the voltage readings, then the system
voltage imbalance and/or inherent capacitor bank imbalance is creating an error volt-
age between the bank neutral and ground. This error is large enough to obscure the
neutral-to-ground voltage resulting from the isolation of successive capacitor units.
Do one of the following:
•
Set the lockout level to a value lower than the lowest voltage just measured. Note
that this means that lockout may occur with fewer capacitor units removed from
service.
•
Set up the unbalance compensation feature, as described in “Unbalance Compen-
sation” on page 12.