Systems & Electronics

The protection relay DIA4L belongs to SIGMA-L digital protection line and it performs three phase overvoltage and undervoltage protection, over frequency and underfrequency protection, residual overvoltage protection; it could be used as interface protection for active Users connected to MV electric power system.

DIA4L protection relay is compliant with Italian document Norma CEI 0-16 (2019-04) in reference to “interface protections”. The user can choose one or more of the functions listed in the following table:

(*) These thresholds are used by frequency thresholds with voltmetric control (81V)

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 – DIA4L manages the following thresholds:

• 2 overvoltage thresholds
• 2 undervoltage thresholds
• 1 + 1 residual overvoltage threshold
• 2 overfrequency thresholds
• 2 underfrequency thresholds
• Frequency thresholds with voltmetric control
• 1 positive sequence undervoltage threshold
• 1 negative sequence overvoltage threshold
• remote trip
• breaker failure

All thresholds have definite-time delay.

Trip condition is shown and recorded with LEDs and with a message on the display.