4 ms·
All those 40 million customers are already on a 50 Hz grid, it's just that the phase of the Ukrainian grid might be slightly different from the European grid. Y
by WJW 5y ago
All those 40 million customers are already on a 50 Hz grid, it's just that the phase of the Ukrainian grid might be slightly different from the European grid. You can (with the correct know-how, training and access to generator controls!) fairly easily get one of the two to speed up or slow down by 0.1 Hz or something like that, wait until the grids match phase and then bring the frequencies back together. Now that they are the same frequency and phase, you can connect the networks just by flipping a switch and provided they were both in balance before the procedure no current will flow initially. Afterwards the two separate networks have effectively merged into one bigger network.
It seems very complicated, but bringing generators and subgrids into sync is something that network operators do all day long. (Ship engineers too, since they can't rely on shore power for obvious reasons! You can have some very "interesting" outages if you forget to synchronize a newly started generator before connecting to the rest of the ship electricity system.)
- flavius29663 5y agoI 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 agoWell, 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 agoSo 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.
- Knemejic 5y agoIs this actually how it is done? I would assume that the complete ENTSO-E grid cannot be perfectly phase-synchronous anyway, simply due to the physical dimension of the grid and the speed of light. I would have guessed that frequency-synchronicity is sufficient for coupling two grids, and then you could use something like a phase shifting transformer to control the power flow?
- numpad0 5y agoSounds like needs to be consistent within each subgraphs of grids and synchronous at connection points
- 323 5y agoSome country interconnections, in particular those to UK and Nordic countries, have the ability to connect even unmatched phases, by for example converting to and from DC (AC -> DC -> AC).
- lxgr 5y agoAustria and the Czech Republic (Czechoslovakia at the time) used to have one of these too: https://en.wikipedia.org/wiki/GK_D%C3%BCrnrohr https://en.wikipedia.org/wiki/GK_D%C3%BCrnrohr
- sebazzz 5y agoThat ability to connect unmatched phases is secondary to the primary function of those interconnects: over those distances it is more efficient to transmit the power in DC instead of AC. [0] [0]: https://en.wikipedia.org/wiki/High-voltage_direct_current#Advantages https://en.wikipedia.org/wiki/High-voltage_direct_current#Ad...
- jamincan 5y agoSometimes connecting unsynchronized grids is the primary reason. The Outaouais HVDC Intertie is only about 35km long, but it allows the import and export of electricity between Ontario and Quebec.
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- bckr 5y agoThis sounds beautiful, like producing music where your instruments are an entire continent's electrical grid.
- aerostable_slug 5y agoUntil you find your inner Hendrix and produce positive feedback on transmission lines.