Systems & Electronics

IAD3N – Digital directional earth fault or directional power relay

The protection relay IAD3N belongs to SIGMA-N digital protection line and it performs functions as directional power relay or directional earth fault relay.


Directional earth fault

67 N

Directional power relay 67 – 32

The protection relay IAD3N is used for the following applications:

  • directional power relay
  • directional earth fault protection in electrical systems with
    • unearthed neutral
    • neutral solidly earthed
    • neutral earthed through a resistance
    • neutral earthed through transformer
    • neutral earthed through Petersen coil

All the functions of the relay are fully programmable by front panel keyboard or through a RS485 serial interface using a personal computer with set-up program; furthermore the relay can be programmed through a remote control and monitoring system.

Thresholds – the IAD3N relay manages up to 3 independent directional thresholds (S1, S2, S3); each threshold is defined by the following programmable information:

  • current threshold Is>
  • voltage threshold Us>
  • characteristic angle and sector width

The thresholds can be programmed as definite time or dependent time (threshold S1 only) in compliance with BS142 and IEC 255-4 specifications (the time delay is function of the measured current and the Is> threshold).

Each definite time threshold delay can be combined with an additional timer controlled by the digital inputs.

The trip of the relay is shown by LEDs and by a message on the display.