A client has recently installed an LV switchboard with an LV REF on the incoming feeder from the (private) transformer.
During commissioning it was found that the relay took considerable time to trip (~300ms) when injected a with small amount over the trip setting; which dropped with increasing current to a more usual time at around 1.5x Is. We are used to electromechanical REF relays which are definite time, but this is an electronic device and while we didn't plot time against current it "felt" almost like an inverse time response for that small window... Is this normal behaviour for electronic REF relays? If so... why?
...And yes we have engaged with the manufacturer, who haven't yet given a definitive response. It is not described in their documentation.
I have an inkling that it's to do with harmonic filtering or sample rates, but could be well off.
(Slightly off-topic but not sure if this is better here or in the Engineering Discussions section in this new system)