3 ms·

I knew they were also on 50Hz, I was just thinking that if they are on a different phase it could blow up or something. But now that you mention some details, i

I knew they were also on 50Hz, I was just thinking that if they are on a different phase it could blow up or something. But now that you mention some details, it doesn't seem that big of a deal anymore, thanks! What happens if they were to connect them while on opposite phases?

WJW 5y ago
Well, if the generators and/or motors of each grid are not in phase with each other then connecting the networks together will cause electricity to flow in such a way that the phase difference disappears. This will speed up the generators that are "behind" and slow down the ones that are "ahead" in terms of the weighted average phase. How big this braking or accelerating force is depends on how much electricity can flow and how "big" the networks are in terms of the total rotational inertia of all connected devices. I once was on a ship where the engineering dept unadvisedly connected a ~1.5 MW diesel generator to the network when it was out of phase and that shook the entire 6000 ton ship. We later calculated that the whole multi-ton rotor had rotated about 60 extra degrees in under a tenth of a second (in addition to already spinning at 50 Hz), so you can imagine the forces involved with that. In practice, there will be humongous circuit breakers that trip to protect the equipment.
- flavius29663 5y ago
  So the result is either really bad...or worse than that: - if the circuit breakers kick in, you might end up with a huge nationwide blackout. Pretty hard to recover from that - but at least you will recover directly in the new grid. - if they don't kick in, you get all the generators in Ukraine + Moldova struggling immensely, possibly breaking their encasings/bearings, a little less for Europe, since they would have more mass to resist this spike.

3 ms·

I knew they were also on 50Hz, I was just thinking that if they are on a different phase it could blow up or something. But now that you mention some details, i

by flavius29663 5y ago

WJW 5y ago
Well, if the generators and/or motors of each grid are not in phase with each other then connecting the networks together will cause electricity to flow in such a way that the phase difference disappears. This will speed up the generators that are "behind" and slow down the ones that are "ahead" in terms of the weighted average phase. How big this braking or accelerating force is depends on how much electricity can flow and how "big" the networks are in terms of the total rotational inertia of all connected devices. I once was on a ship where the engineering dept unadvisedly connected a ~1.5 MW diesel generator to the network when it was out of phase and that shook the entire 6000 ton ship. We later calculated that the whole multi-ton rotor had rotated about 60 extra degrees in under a tenth of a second (in addition to already spinning at 50 Hz), so you can imagine the forces involved with that. In practice, there will be humongous circuit breakers that trip to protect the equipment.
- flavius29663 5y ago
  So the result is either really bad...or worse than that: - if the circuit breakers kick in, you might end up with a huge nationwide blackout. Pretty hard to recover from that - but at least you will recover directly in the new grid. - if they don't kick in, you get all the generators in Ukraine + Moldova struggling immensely, possibly breaking their encasings/bearings, a little less for Europe, since they would have more mass to resist this spike.