# Phase Sync Power Stations



## CalgaryPT (Feb 16, 2021)

There has been a lot of VFD discussion on the forum. I haven't used one in years as I no longer have any 3 phase machines. However, one of your posts the other day got me thinking about a topic I always took for granted but never researched: how do they phase-sync different power stations (i.e., big generators) on the electrical grid? The brown outs in Texas yesterday and the issues they are having with their grid due to snow (yes,_ snow and alligators in the same state_) were a big topic of discussion on the snowblower forum I hang out on as well. While driving back from Metal SuperMarkets in Calgary today and watching the steam plumes along Stoney Trail from the Enmax generating station, I got thinking about this topic more and more.

Inverter type gas generators like my Honda EU2000 have sync modes on them now where you can connect a cable and the electronics do this automatically. (Mine is actually the older version that can't be sync'd, but you get the point.) But how do you do this, and how was it done in the old days before sophisticated electronics? Those of you old enough to remember the 1998 Quebec ice storms know that a big part of recovery was bringing the grid back online. The Quebec grid was more isolated from other grids at the time, so tapping into alternative grids was problematic. And for you real old timers like myself, you may recall the New York City Blackout that paralysed the Big Apple in 1977. Phase shift there severely complicated bringing the power back, and when they didn't get it right—it caused even more damage. Damage can be really expensive too; in New York they had subterranean transmission lines (which aren't preferred due to heat dissipation issues). So a screw-up here means somebody's getting called into a supervisor's office for a chat.

Until this problem was solved—and long after Tesla's AC based grids became the standard—there was no redundancy or ability to connect and leverage other grids. Whenever I look at those satellite maps of the abandoned Love Canal in New York State, I think how far we have come with our electrical grids.

Here's a great video that explains and illustrates the problem and how you solve it in a way that the average guy can understand. There are even cooler demos in the latter parts of the series.


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## PeterT (Feb 16, 2021)

Not a pretty week down there.

https://oilprice.com/Energy/Energy-General/Texas-Freeze-Raises-Cost-Of-Charging-A-Tesla-To-900.html


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## Dabbler (Feb 17, 2021)

The basic concept is that the grid phase is sensed for crossover point and direction before the connection is made, and then the source is altered to meet that time base.  It is maintained for drift by interrupting the injection current near the zero point and comparing the generator's zero and polarity versus the grid's and adjusting before injection can begin again.

On really big injection points such as the Alberta DC link, it is a little more sophisticated, but this alignment happens very frequently, such as every crossover, or every second crossover.

This isn't very hard or needs sophisticated electronics.  it is the same for solar panels on your roof that inject power into the grid.


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## Brent H (Feb 18, 2021)

On the ship we are phase synchronizing all the time.  Between generators and we can synch with shore power if necessary for a very short period of time ( less than 30 seconds) as we are not set up to power the city.  
Between generators it is a “simple” matter of adjusting the speed of the on coming generator slightly slower that the load gen and then closing the breaker just before (say 10°) before top dead centre of the sine wave (matching the phase angle). The generators will match up and the wave forms will synchronize - all good.  Electricity like to run that way and the generators will balance out the loads and power factors etc.  
If we tie up at a the dock where a phase is out - say we are ABC and the station is wired ACB we can rotate a large phase sequencer switch to match up the phases. Then do the same with our generator as described above to match the frequency and close the breaker.  

that is a very simple explanation but it is not as complicated as you would think as electricity like to run in phase.  There are many highly dangerous things that can happen if you decide to close the breaker “out of phase” or 180° out of the proper phase angle or if you reverse power the generator (slow it down so the shore power wants to turn the generator into a motor). - it can be exciting in a bad way.


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## Hacker (Feb 18, 2021)

That is pretty much what utilities do but on a little larger scale. We get the generation to slow down or increase their speed and match the voltages then close the synchronizing breaker to tie the systems together. This can be a real hit and miss if the generation is in area where the system is weak  and you are trying to sync two areas together.


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## Johnwa (Feb 18, 2021)

For the isolated diesel plants in the Yukon we used 2 light bulbs when synchronising generators. The bulb was connected  between the two generators but on the same phase.  When the bulbs went out the breaker was closed manually.  Some operators were good at it, others made the buildings shake.  The breakers were originally used in the Dawson City gold fields.


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## Hacker (Feb 18, 2021)

When I first went up there most of the isolated plants had that. The Mayo Generating station used that as well, but it did have an auto sync that took forever to close so we just did it manually with the lights and sync scope and closed at 10 to the hour. By the time I left the Yukon most of that had been replaced with an automated load sharing system that could be operated out of Whitehorse.


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## Hacker (Feb 18, 2021)

When were you up in the Yukon John?


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## Johnwa (Feb 18, 2021)

I was there in the early 1980s.  I was with Yukon electrical.
How about you?


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## Hacker (Feb 18, 2021)

Was there from 87 to 99. I was with YECL as well but I went up to Mayo as YECL had the contract to manage and run the old NCPC assets for the Yukon Gov't. Spent a couple years in Mayo then moved to Whitehorse.


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## Hacker (Feb 18, 2021)

CalgaryPT said:


> There has been a lot of VFD discussion on the forum. I haven't used one in years as I no longer have any 3 phase machines. However, one of your posts the other day got me thinking about a topic I always took for granted but never researched: how do they phase-sync different power stations (i.e., big generators) on the electrical grid? The brown outs in Texas yesterday and the issues they are having with their grid due to snow (yes,_ snow and alligators in the same state_) were a big topic of discussion on the snowblower forum I hang out on as well. While driving back from Metal SuperMarkets in Calgary today and watching the steam plumes along Stoney Trail from the Enmax generating station, I got thinking about this topic more and more.
> 
> Inverter type gas generators like my Honda EU2000 have sync modes on them now where you can connect a cable and the electronics do this automatically. (Mine is actually the older version that can't be sync'd, but you get the point.) But how do you do this, and how was it done in the old days before sophisticated electronics? Those of you old enough to remember the 1998 Quebec ice storms know that a big part of recovery was bringing the grid back online. The Quebec grid was more isolated from other grids at the time, so tapping into alternative grids was problematic. And for you real old timers like myself, you may recall the New York City Blackout that paralysed the Big Apple in 1977. Phase shift there severely complicated bringing the power back, and when they didn't get it right—it caused even more damage. Damage can be really expensive too; in New York they had subterranean transmission lines (which aren't preferred due to heat dissipation issues). So a screw-up here means somebody's getting called into a supervisor's office for a chat.
> 
> ...


I spent 12 years in various positions, some as an operator in a transmission control center. I can tell you that any mistake made operating on the transmission grid involved an investigation and the trip to the supervisors office was usually just the beginning of the experience. They usually ended up on the company president's desk and as well as the Alberta Electric System Operator. If it was a biggie then the lawyers got involved. I don't miss that! LOL


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