Systems & Electronics

DIA4N – Interface protection relay according to CEI 0-16 Norm (ed. 3)

The DIA4N protection relay belongs to the SIGMA-N digital protection line and it performs three phase overvoltage and undervoltage protection, overfrequency and underfrequency protection, residual overvoltage protection; it could be used as interface protection for Users connected to MV electricity network.

The DIA4N protection is according to requirement by CEI 0-16 Norm (ed. 3).

The user can choose one or more of the functions listed in the following table:



Overvoltage protection


Undervoltage protection


Residual overvoltage protection

59N (59Vo)

Overfrequency protection

Underfrequency protection 81<

Voltage unlock frequency protection


Positive sequence undervoltage protection (*)


Negative sequence overvoltage protection (*)



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

Thresholds and functions – the DIA4N relay manages the following thresholds and functions:

  • 2 overvoltage thresholds
  • 2 undervoltage thresholds
  • 1 residual overvoltage threshold
  • 2 overfrequency thresholds
  • 2 underfrequency thresholds
  • Voltage unlock frequency protection
  • 1 positive sequence undervoltage threshold
  • 1 negative sequence overvoltage threshold
  • Remote trip

All thresholds have definite-time delay. Trip condition is shown and recorded with LEDs and with the message on the display.