NRC-511 Digital Capacitor Protection and Control Unit

Nanhong Electric NRC-511 Digital Capacitor Protection and Control Device

I. Overview
1.1 Scope of Application
The NRC-511 Digital Capacitor Protection and Control Device is suitable for non-directly grounded or ungrounded systems with voltage levels of 110kV and below. It serves as a protection and control device for shunt capacitor banks, which can be centrally grouped on panels or installed locally in switchgear cabinets. It fully supports integrated substation and distribution automation systems.
1.2 Device Function Configuration
1.2.1 Three-Stage Overcurrent Protection:
Used for three different levels of fault severity. Each stage of protection can be individually enabled or disabled, with protection settings and operating delays independently adjustable (Note: The current quick-break delay is fixed at 0S).
1.2.2 Overvoltage Protection:
To prevent damage to capacitors caused by steady-state overvoltage in the system, overvoltage protection is provided. The protection includes an adjustable delay and can be enabled or disabled via protection settings. To avoid misoperation of overvoltage protection during single-phase grounding when using phase voltage, overvoltage protection uses line voltage.
When the measured line voltage exceeds the overvoltage setting, the timer is activated, and after the overvoltage delay, the output relay operates.
When overvoltage protection is activated, the circuit breaker position must be checked; the output relay will only operate if the circuit breaker is in the closed position.
1.2.3 Undervoltage Protection:
To prevent the capacitor bank from losing power after a system fault causes the line to disconnect, and then the line reclosing energizes the busbar, subjecting the capacitors to switching overvoltage and damage, undervoltage protection is provided in the device. The protection includes an adjustable delay and can be enabled or disabled via protection settings. To avoid misoperation of undervoltage protection during single-phase grounding when using phase voltage, undervoltage protection uses line voltage.
When the measured line voltage falls below the undervoltage setting, the timer is activated, and after the undervoltage delay, the output relay operates.

When undervoltage protection is activated, the circuit breaker position must be checked; the output relay will only operate if the circuit breaker is in the closed position.
1.2.4 Unbalance Voltage Protection, Unbalance Current Protection:
To enable the capacitor switch to trip when three-phase current unbalance or grounding faults occur in the system, the device includes unbalance current and unbalance voltage protection.
The protection can be set to operate for trip output or alarm.
When the measured zero-sequence current exceeds the unbalance current setting, the timer is activated, and after the unbalance current delay, the corresponding output relay operates.
When the measured zero-sequence voltage exceeds the unbalance voltage setting, the timer is activated, and after the unbalance voltage delay, the corresponding output relay operates.