Compensation impedance (IC)


Compensation impedance (IC)

Downstream of the HVB/HVA transformer, compensation impedances equip MV networks with neutral point connection (aerial-underground rural networks).

Developed as part of the Enedis MALTEN project and installed in source stations, compensation impedances allow:

  • The creation of an artificial neutral point separate from the HVB/HVA transformer.
  • Compensation of the network's total capacitive current through automatic tuning.
  • The operating of zero-sequence protection, by ensuring a sufficient active current in the single-phase fault.

Main characteristics

  • Phased compensation impedance, adjusted using vacuum switches activated by a command control switch connected to the network's permanent auscultation system.
  • Hermetic materials, in a mineral oil bath, for an exterior installation.
  • ONAN cooling mode.
  • Lifting by the 4 rings located on the top cover.
  • Primary rated voltage for IC of 600 A and 1000 A: 21400 V.
  • Frequency for IC of 600 A and 1000 A: 50 Hz.
  • Neutral rated current: from 80 to 600 A for IC of 600 A / from 80 to 1000 A for IC of 1000 A.

Command control function:

  • Translation of command orders from the Automatic Tuning System (SAA) into IC switch opening and closing orders.
  • Command in manual mode.
  • Protection against series resonance phenomena via an overvoltage detection function causing instantaneous discordance.
  • Sending of information to the source station (IC position).


  • Ensures compliance with the maximum 1500 V requirement of overvoltages on the LV network following a phase-earth fault on the MV network.
  • Protects people by preventing touch voltage (MV grounds).
  • Prevents hazardous voltages on telephone networks due to the earth coupling phenomenon.
  • Reduces the destructive effects of phase/earth faults by limiting their intensity to a value below 40 A (under full zero sequence voltage).
  • Improves supply quality by promoting the automatic extinguishing of most single phase faults.
  • Reduce size and weight: simplified transfer from IC 600 A to 1000 A with, for both items of equipment, identical bases and similar sizes (length and width).


  • Rural environment
  • Peri-urban environment

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