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Capacitor Protection Relays

Trench’s capacitor filter protection relay CPR500 is specifically designed to provide comprehensive protection of medium and high voltage capacitor banks and filter installations.

The non-availability of capacitor/ filter banks can be extremely costly for electricity users.

The loss of capacitors and/ or reactors possibly results in major penalties in maximum demand charges, effects plant production , disables the operation of complete electric systems and is often also associated with unacceptable thermal loading of transformers, cables and switchgear, coupled to higher voltage drops, unacceptable voltage regulation and excessive harmonic distortion.

This necessitates an optimized protection of capacitor banks and filter installations under all possible operating conditions.

General features

The CPR 500 provides comprehensive protection for the capacitive, inductive and resisive elements of three phase medium and high voltage shunt capacitor banks and harmonic
filter circuits.

The capacitor banks may have a single star, double star, delta or “H” configuration, with internally fused, externally fused or unfused capacitor units.

Design features

  • Capacitive touch user interface
  • Graphical display
  • MODBUS RTU default to all expansion modules
  • IEC61850 Server
  • Additional I/O’s
  • USB communications interface
  • Multi language support
  • Removable GUI (panel door mount)
  • Communication expansion modules to Include:
    – IEC61850 with RS485
    – Ethernet (TCP/IP) with RS485

Protection Functions

  • Peak repetitive overvoltage protection to the 50th harmonic
  • Overcurrent, undercurrent and earth fault protection
  • Neutral unbalance protection with residual compensation
  • Line unbalance protection
  • Thermal protection for capacitor, inductor & resistor elements
  • Dual breaker fail protection with programmable logic
  • Capacitor re-switching protection

Capacitor and filter banks need to be protected against disturbances to prevent unscheduled outages. The CPR 500 provides extensive features to ensure troublefree operation.

System protection

The CPR 500 functions are designed to limit the possible damage to capacitors in a power factor correction system.
Noting the CPR 500 does not have any facility to control power factor.
The main objective is to remove the protected equipment from service before damage occurs.

The CPR 500 has two types of protection modes residing in the firmware, either one can be selected to suit the protection requirements. The NORMAL MODE (N mode) covers the common protection applications. The H-BRIDGE MODE (H mode) is specifically for H configuration capacitor banks.

There can be more than one CPR 500 used in a protection scheme that may require both N & H protection, or where there are parallel circuits and fine protection is required in one leg of the parallel circuit.

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