IFD4N – Digital multifunction protection relay for MV lines
The multifunction protection relay IFD4N belongs to SIGMA-N digital protection line and it performs functions as 2phase overcurrent and directional earth fault relay for MV lines. IFD4N relay is compliant to the CEI 0-16 norm.
The user can select one or more of the functions listed in the table below:
| FUNCTIONS | ANSI |
|
Overcurrent |
51 |
| Short circuit | 50 |
| Directional earth fault | 67N |
| Overcurrent earth fault | 51N |
| CB pole wearing index (121) |
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 – IFD4N manages the following thresholds:
- 3 phase overcurrent
- 3 directional earth fault
- 3 overcurrent earth fault
All thresholds are definite time, and for the first phase overcurrent and the first directional earth fault inverse time characteristic is available; each of them 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.
The directional earth fault function is used in electrical systems with:
- unearthed neutral
- neutral solidly earthed
- neutral earthed through a resistor
- via earthing transformer
- neutral earthed through Petersen coil
