Disturbance Recording

Yes, although newer digital relays have significantly inproved the amount of event recording of which they are capable, they are still limited in what they individually store. Also, they know nothing of what is happening in other relays and metering in the station. Therefore there has developed an opportunity for the "digital fault recorder" (DFR) or disturbance recorder as you call it.

One advantage of the DFR is that it synchronizes all of its inputs to one, usually GPS-controlled, clock. That way all the different events and disturbances are stored in a wya that you can see the relationships in time between them. Individual relays may be GPS synchronized, but I have seen too many situations where something has caused a particular relay's clock to be incorrect, so its time stamping is inaccurate.

Also, the DFR collects all this information in one place, so that you can do a single download of all of the happenings, both digital (relay contact activations, etc.) and analog (metering quantities I, V, F, etc.). If not for the DFR, you might have to download individually from multiple relays - very inconvenient!

Utilities are looking to run a reliable system. Anything that can give them quicker access and more accurate information on what caused a problem will allow them to correct it and improve functionality so that it doesn't happen again.