> it's difficult to test this equipment
Can't you just flip the circuit breaker or just pull the plug out? Or does a real power outage usually look different to that in some way, like a surge followed by a shutoff?
Can't you just flip the circuit breaker or just pull the plug out? Or does a real power outage usually look different to that in some way, like a surge followed by a shutoff?
In our small data centre we have a board with five lights and a key. You turn the key and the mains is cut off. The lights give the status. The UPSs beep for a few seconds "on battery", the genny fires up in the boiler room and when it stabilises, it takes the load. We leave it running for 5-15 minutes, go out and check the fuel levels and top up accordingly. It's diesel so safe to hot refuel. When done, turn the key back and then the UPSs take the load again and then hand back to the mains. The genny runs for another 15 minutes and then shuts down. That should avoid flip flopping.
You then fill in the test form on our wiki and job done. We do it weekly to fortnightly. An ESP8266 based thingie reports status back to the central monitoring (GPIOs and ESPHome -> Home Assistant)
The customer was running the generators right at the maximum capacity, and we'd see really, really odd things on the power lines. Some times a surge like you mention, sometimes changes to the frequency, sometimes changes to the voltage. We discovered all sorts of weird brownout conditions in our devices.
Initially, there's a fault, say, a tree contacting a wire. This conducts a bunch of current to ground, the voltage in part of the network sags a fair bit, and a protective relay senses the overcurrent and opens the circuit. This happens in a second or two, and your power goes out. You may notice lights dimming or flickering in the instant beforehand.
But, many faults are transient. Perhaps that tree branch finished falling, and is no longer against the wire. So the protective relay performs a "reclose" operation, where it turns the power back on for a moment and measures the current. There's normally a huge starting inrush as motor-driven appliances restart, so it waits a moment before sampling the current, and this is the period when the power comes back on for a few seconds. (It's probably pretty nasty power during this interval, too.)
If things are good, hey, you're good! A brief outage while waiting for the fault to clear itself, and then everything's back. The operation will be reported to the dispatch center, and someone may come out to inspect the area in case there's damage.
But if the fault is still there, and after a moment the current is still way higher than it should be, the recloser opens again, and this time it stays open. Gonna need a crew to move that tree, and then they'll manually try again.