Examples of application of preventive alarm relay mirroring modes

When the device is inoperative, the system should automatically switch to another device by managing exclusions using the injection inhibition input. See Injection inhibition input (Inhibit. Input) for more information on injection inhibition input.

Set the preventive insulation alarm relay to mirror mode and wire the relays in series to create a logical AND function. It is advised to configure the insulation alarm relay in failsafe mode and wire both relays in (NC/C). In this case, the logical function returns true only when the device is inoperative or de-energized, or when a special status is active.

The following wiring diagram is an example of the device wired in standard mode:

Mode	Input	State
Mode	Input	No fault	Preventive alarm	Alarm	Inoperative product	No power
Standard	PLC 1	1	1	1	0	0
Standard	PLC 2	1	1	0	0	1

The following wiring diagram is an example of the device wired in failsafe mode:

Mode	Input	State
Mode	Input	No fault	Preventive alarm	Alarm	Inoperative product	No power
Failsafe	PLC 1	0	0	0	1	1
Failsafe	PLC 2	0	0	1	1	1

ALARM=(RelayState:ON) || ((StatusInput:CLOSED) & (RelayState:OFF))

An insulation alarm is detected when both PLC inputs are at a logic 1.
A product failure is detected when PLC input 1 is a logic 0.