UHF4N – Digital multifunction protection relay
The multifunction protection relay UHF4N belongs to SIGMA-N digital protection line and it performs functions as 3phase overand undervoltage, residual voltage (earth fault), over and underfrequency and max frequency rate of change.
The user can select one or more of the functions listed in the table below:
| FUNCTIONS | ANSI |
|
Overvoltage |
59 |
|
Undervoltage |
27 |
|
Overvoltage (3 out of 3ph) |
59 |
|
Undervoltage (3 out of 3ph) |
27 |
|
Residual voltage |
59N (59Vo) |
|
Overfrequency |
81> |
|
Underfrequency |
81< |
|
Frequency rate of change |
df/dt |
All the functions of the relay are fully programmable by front panel keyboard or through a RS485 serial interface by using a personal computer with set-up program; furthermore the relay can be programmed through a remote control and monitoring system.
Thresholds – UHF4N manages the following thresholds:
- 2 phase overvoltage
- 2 phase undervoltage
- 2 voltage presence
- 2 voltage absence
- 2 residual voltage
- 2 overfrequency
- 2 underfrequency
- 2 frequency rate of change
All thresholds are definite time; 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.
