I know that the Minimum Operating Voltage setting is usually implemented to avoid unwanted tripping while the circuit is de-energised. I think I'm right in saying that, if we did not have this setting then, the relay would trip out whenever the circuit was de-energised and it would then be necessary to either disable the undervoltage protection or energise the circuit (using another feeder) to re-close the relay.
That all seems reasonably straightforward but I am curious as to why you would ever want to set the minimum voltage to anything greater than 0.00xVT? Please can someone advise?
I was previously assuming that the control logic for the protection relays would require the voltage to be greater than 0.00 x VT. However, it would make more sense if the measured voltage had to be greater than or equal to 0.00 x VT. This would mean that the 0.00 x VT setting effectively disables the minimum operating voltage requirement.
If this is correct, can anyone recommend a way of determining a suitable minimum operating voltage value?