Continental Europe successfully synced with Ukraine and Moldova power systems | Hacker News Reader

Continental Europe successfully synced with Ukraine and Moldova power systems

entsoe.eu

201 points_Microft43 comments

Background article from a week ago:

https://www.wired.com/story/the-race-to-rescue-ukraines-powe...

The Race to Rescue Ukraine’s Power Grid From Russia

In late February, Ukraine began a long-planned 72-hour test to unhook its electricity grid from Russia’s. Then the invasion started.

Much better article. It says they have a 2000 MW transmission line between Ukraine and Europe.

I know almost nothing about this, so this is a genuine question. Why do you say 2000 MW instead of 2 GW? Convention? Is 2 GW incorrect?

They're equivalent. Neither is more correct. Megawatts are a bit more understandable to the layperson, for the same reason that "a million dollars" is more understandable than "a billion dollars". A megawatt is about 1000 homes[1]. A gigawatt is a city.

[1]https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 A US Household uses slightly more than a kilowatt on average, though obviously peaks and troughs are well off that.

I guess it's similar to how we in the metric world would say "2000 kilometres" and not "2 megametres" (certainly not in an everyday context).

> "a billion dollars"

This is only tangentially related to your point, but the word "billion" often gets mistranslated due to its two distinct meanings (long vs short scale). This could be another reason to avoid it.

https://en.wikipedia.org/wiki/Billion

The best distinction I’ve read between a million and a billion came from Bill Bryson. He noted that there are 1 million seconds in 11 days. There are 1 billion seconds in 32 years.

This seems like a huge engineering challenge, imagine synchronizing 40 million customers at 50 Hz

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.)

This sounds beautiful, like producing music where your instruments are an entire continent's electrical grid.

Until you find your inner Hendrix and produce positive feedback on transmission lines.

Is 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?

As far as I'm aware this is how grid operations are done in the overwhelming majority of the world. You spin a generator up to speed, match phases and close the switch to connect it to the rest of the network. Due to how electricity works, if any connected generator is slightly out of phase with the rest that will generate currents causing it to pulled back into phase in a closed feedback loop. So while it is technically possible for a generator to be out of phase with the network, it can never be outside of phase for very long because literally all the other generators on the network are pulling it back into phase.

If the grids are particularly far from each other and/or with differing frequencies, a DC high voltage line can be used instead but that is certainly not the most used method.

You only need to match phase at the connection point, so the phase of the grid in France doesn't really matter (as long as ENTSO-E isn't destroying itself before you do anything).

This does get much trickier if you have multiple connection points and it is impossible to be synchronized at all of them because the in-grid distance between the two points is different on the two grids. Then you definitely do need fancier tricks.

True, but you need to have a very large unbalanced grid for that to occur: at the grid frequency (50 Hz), the corresponding wavelength is 6000 kilometer. So assuming that math is correct, you would need a path length difference of 3000km between two transformers to get full phase inversion between the paths.

That's more than twice the max diameter of the entire European grid (Tunesia-Gibraltar-Turkey seems the longest path). So as long as there's transformers every few hundred kilometer, and multiple paths between most of the connection points, the overall phase synchronization should be adequate to not need those fancier tricks.

Some 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).

That 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#Ad...

Sometimes 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.

Even more fun is that Denmark despite its' very tiny size is split in two when it comes to electricity. West Denmark is connected with East Denmark through HVDC.

This was how the Tres Amigas Superstation was supposed to work.

Unfortunately, ERCOT decided they didn't want to be subject to the same regulations as the Eastern and Western interconnects, so the project collapsed.

Austria and the Czech Republic (Czechoslovakia at the time) used to have one of these too: https://en.wikipedia.org/wiki/GK_D%C3%BCrnrohr

I looked into this once, and they .... just don't worry about it.

Each generator just matches whatever it sees. If you are trying to match two other generators (like in a triangle, and due to the speed of light it's impossible for all to be perfectly in sync), then it matches to an average of the two, and apparently that works.

Sounds like needs to be consistent within each subgraphs of grids and synchronous at connection points

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?

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.

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.

It's not as huge as all that, most of Europe is already similarly synchronized and Ukrenergo was already running at 50 Hz. The longer term concern is communication and coordination between the RTOs in Europe and Ukraine, as Ukraine must now respond to grid conditions and act to maintain as spelled out by complex and detailed operating procedures.

Actually syncing up is more of a case of putting in some high resolution meters at the interconnect substation, or maybe some phase shifting transformers, and adjusting the Ukrainian side's frequency by a few micro-hertz an hour until the phase angles are close enough by setting frequency targets at the largest generators. Something similar happens all the time in wide area grids when generators are brought back on line.

You only need to adjust one generator to change the frequency, since Ukraine grid is in balance simply adding or removing additional power will alter the frequency.

Controlling the voltage at the point of synchronization is probably done with tap changers on transformers but would be more complicated to ensure that power flows over the transmission line once it is connected are as desired.

Looking forward to switching Latvia/Lithuania/Estonia from BRELL.

I am curious. What effects will that have?

So far Baltics' grids frequency is stabilised by Russian massive hydro plants. Technically Moscow can bring down Baltics grids if they want to and try to hard enough. Baltics could try to disconnect, but there's not enough stable power generation to keep frequency stable permanently. Big part of electricity is imported from Scandinavian hydros and they can't be utilised for stabilising the frequency.

Another side effect - that means Kaliningrad would be unhooked from Russian mainland grid. They already have enough power generation on-site to keep the lights on, but I'm not sure if they have the means to stabilise frequency and enough redundancy if something bad happens. On top of that, political question comes up if it would become it's own tiny grid or become synchronised with continental europe grid too. Major Russian navy base attached to NATO-controlled grid may not sound cool for Russians :)

Independence from Russia, ability to import/export electricity from/tu EU

There're import/export links to Sweden, Poland and Finland already. But they're connected through a converter rather than directly.

Scheduled for 2025 but I do hope it gets accelerated.

It was already delayed several times because of EU fears of Kaliningrad and Russia response. Hopefully now our politicians have enough arguments to make it happen.

While at it, it may be good to stop the special permit for visa-free train from Russian mainland to Kaliningrad.

It might be a tactical distraction that is needed at this point in time.

Military traffic is out of scope, so it'd be similar inconvenience as air space closure. But every tiny bit helps.

This is long overdue. As well as unhooking from Russian gas.

Lithuania is already unhooked from Russian gas. LNG terminal in Lithuania can supply enough gas for all 3 Baltic states and there's a massive gas storage in Latvia. All 3 gas grids are well interconnected as well.

Russian gas through pipe were cheaper than fully loading LNG terminal though.

True. But the lack of political will and corruption at all levels is what hampers the process. In my country which lies slightly north of Lithuania, that is huge problem. There, similarly as in Germany former heads of government have lucrative positions in Russia-connected gas companies still.

Considering how quick this took place, it’s almost as if someone had actively interfered or otherwise prevented Ukraine from being in position to sell its excess/offpeak nuclear and gas electricity to countries further east!

Recall that someone seized one of the nuclear plants, and technical staff are now effectively their prisoners.

https://www.ukrinform.net/rubric-ato/3431207-invaders-keep-s...

How secure is this? Is it actively supporting Kyiv? Eastern Ukraine?

"and the adoption of risks mitigation measures."

i.e. We really need this yesterday. Stand back, let's see if it works.

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