The instrument in 6 DIN module format is an Interface Protection System (SPI) that complies with CEI 0-21 edition 2019-04, with respect to three-phase(*) low-voltage (LV) systems at
50 Hz, with or without neutral (Vn=400V).
It is placed to protect between generation systems and the
public grid, intervening by separating the two should the latter have problems such that one or more of the protection
thresholds provided are exceeded with respect to the voltage
and/or frequency value.
Its operation on the grid is regulated by Terna’s Annex 70.
The protection acts on the contact opening mechanism of
the Device Of Interface (DDI), while also monitoring its actual
state by means of a feedback signal that it reads on its dedicated input. If, as a result of the protection’s intervention, the
opening command is sent to the DDI but it does not detect
it, a second opening command is sent for a device called the
‘back-up’ device that should ensure the generator’s fi nal di-
sconnection from the public grid.
The protection thus has:
- 3 concatenated voltage measurement inputs, 400Vn.
- 4 digital inputs for mechanical or NPN contact, respectively named “Remote, “Local Command,” “External Signal,” or more simply redefi ned as “Window Selection Frequency” and finally “DDI feedback.”
- 2 relay outputs, referred to as “DDI Command” and “Reverse Command”
- 1 RS485 serial communication port, with Modbus RTU / ASCII communication protocol.
- 1 alphanumeric LCD display with 2 lines of 16 characters each, backlit.
- 3 keys for managing the display and programming of parameters of operation.
- 1 Signal LED.
(*) For single-phase operation, refer to the user’s manual.
