Utility Selects S&C BankGuard PLUS® Control as Its Standard Substation Capacitor Bank Protective Device.

A large overseas utility recently evaluated capacitor bank protective devices, and selected the S&C BankGuard PLUS Control for its standard substation capacitor bank design.

They considered an alternative device utilizing a general-purpose overcurrent relay, which is applied with a very-low-ratio CT to sense the small differential current flowing in the neutral connection. But the full-voltage-rated CT provides poor sensitivity and accuracy with substation capacitor banks. And the general purpose relay operates much too fast in this application, and can give false responses to transients.

The BankGuard PLUS Control, on the other hand, uses a 15 volt-ampere S&C Potential Device connected between the capacitor-bank neutral and ground to detect and alarm on isolation of the first faulted capacitor in the bank. Capacitor replacement can be performed at a convenient time, because the bank is still operational. If the alarm is disregarded, the BankGuard PLUS Control locks out the bank when the maximum recommended capacitor voltage has been exceeded.

The BankGuard PLUS Control includes an unbalance compensation function that, with the addition of station-bus voltage monitoring devices, detects and compensates for the unbalance voltage between the capacitor bank neutral and ground caused by fixed system voltage unbalance and/or inherent capacitor bank unbalance.

The BankGuard PLUS Control also includes a gross overvoltage protection function that bypasses the lockout level and timing-control logic to immediately lock out the capacitor bank if a flashover of series groups occurs within the bank.

The BankGuard PLUS Control allows full SCADA communication via DNP 3.0 protocol. The control can be configured using the front panel display and keypad or with a computer running IntelliLINK® Setup Software. IntelliLINK also lets you access historical and real-time data and troubleshoot equipment.

The BankGuard PLUS Control replaces S&C Automatic Control Devices — Type UP, GP and UPR. It is dimensionally identical to those devices and uses essentially the same field wiring.