Mains monitoring devices

How about an inductive pickup round a meter tail, and a bit of home-brew electronics to drive the contact input on the UPS card? Some APC cards have an input you can read via SNMP. Then you get visibility of upstream of the CU.

I thought of that. But in theory you want to measure voltage, not current. Depends what other current would still be drawn if the MCB tripped.

Yes, inductive coupling wouldn't work because the current can get very low outside office hours: just things like the fridge on.

I had thought of capacitive coupling through the cable insulation to light a neon bulb. Like an unpowered volt-stick.

Do you have a blinkenlight on the leccy meter that you could stick an LDR to, and send a warning message if you don't get a blinken within x minutes?

Still only measures current - albeit even very low amounts over a timespan of a minute or so - but would give you a signal before the CU

Owain

Yes, but it's a three-phase meter (it's a big office, and has a different phase for each floor) and power cuts often only affect a single phase. The LED will still flash if there's any active phases and some load (and there's always some, even if it's just the fridge or something).

The meter has LCD indicators showing if each phase is present, but they are really small and are not backlit, so this won't work.

Fit an 'Owl' Three phase power monitor. It uses clip on sensors just like the domestic single phase ones, and do some clever monitoring on its radio linked display. I use one of these to monitor 3 phase power consumption of various machine tools in my workshop, and have an 'interposer lead' I move from machine to machine that give me access to the three insulated power cores so that I can clip on the sensors - used it for a year or two and it's performed faultlessly.

Andrew