Starting this thread as not de-rail another one. How do you guys set the reclose logic for two terminal 69 and 115kv lines with non communicating, non PLC relays? The desired outcome is to have only one relay do a single reclose attempt after 30 seconds, and once the line holds for 20 seconds have the other relay close its breaker after a sync check. Ie, have the remote relay not reclose but also not lockout.
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Relcosing logic for 311C 1
- Thread starter Mbrooke
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davidbeach
Electrical
Half a dozen or more ways to skin that cat, but all of them require a line VT. Probably the easiest is to set one end to reclose at 30 seconds and include allowing it to close into a dead line and a 50 second reclose at the other end that requires a hot line. Whether or not you want hot line-dead bus reclose in addition to synch checked hot-hot is up to you.
You can get fancier and do a stall on dead line and have a 20 second reclose at the second end.
You can get terminally fancy and watch for the line to come hot, then drop out again, and then drive to lockout. That will fail you now and then for various reasons.
We've gone to a fast end-slow end approach, but the slow end is only 30 cycles slower than the fast end. We've been using SOTF longer than we've been doing the fast-slow, so if the fast end closes into a fault, it will be open again long before the 30 cycles has elapsed.
We do, however, have longer "waits" when the slow end is at a plant, we may wait 15 seconds in that case to make sure the line is going to hold.
If you're going to have 20 seconds between recloses, you probably want a reclose reset time longer than that, perhaps 30 seconds.
You can get fancier and do a stall on dead line and have a 20 second reclose at the second end.
You can get terminally fancy and watch for the line to come hot, then drop out again, and then drive to lockout. That will fail you now and then for various reasons.
We've gone to a fast end-slow end approach, but the slow end is only 30 cycles slower than the fast end. We've been using SOTF longer than we've been doing the fast-slow, so if the fast end closes into a fault, it will be open again long before the 30 cycles has elapsed.
We do, however, have longer "waits" when the slow end is at a plant, we may wait 15 seconds in that case to make sure the line is going to hold.
If you're going to have 20 seconds between recloses, you probably want a reclose reset time longer than that, perhaps 30 seconds.
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- #3
David Beach said:
Will anything be gained or have to be changed in settings by having a set of 3 phase VTs on the line and a single VS on the bus? This is a straight (simple) bus system.
Is there any benefit of having the relay drive to lockout vs having it so the relay will automatically come back in once the line is energized say several hours latter after repair?
One possible issue I see arising here is that with a single VS and a bolted B phase fault or a bolted 3 phase fault with 3 phase VTs that the voltage may not rise high enough to assert drive to lockout. I am guessing this is what you were referring to regarding failing?
Makes sense and I will keep this in mind.
davidbeach
Electrical
As long as you have voltages on both side of the breaker and keep straight which is bus and which is line it doesn't matter which side has the three-phase and which side has the single-phase. With simple bus I've always seen the three-phase on the bus since only one three-phase set is necessary, but there's no inherent reason why you couldn't put three-phase sets on each line.
We try to limit automatic operations to the period immediately following the fault. Once people might have arrived at the station we don't want an auto reclose well after the fact. But if you've got a really remote station with no SCADA control it might be desirable to have it auto close once the line comes hot.
We try to limit automatic operations to the period immediately following the fault. Once people might have arrived at the station we don't want an auto reclose well after the fact. But if you've got a really remote station with no SCADA control it might be desirable to have it auto close once the line comes hot.
If you have the Three PT's on the line, then you really need to use SOTF because a set of grounds left on the line, and someone closes the line, many parts of the protection will be delayed as the PT's attempt to energize.
I agree with david, that you want a timer to allow the second reclose breaker to expire if the line does not come and stay hot.
I agree with david, that you want a timer to allow the second reclose breaker to expire if the line does not come and stay hot.
bacon4life
Electrical
What drives your 30 second reclosing window? It seems fairly long.
Automatically restoring the second terminal via sync check might be worthwhile if it saves operators/dispatchers significant time during restoration. Delayed automatic reclosing of the first terminal into a dead line seems risky.
Automatically restoring the second terminal via sync check might be worthwhile if it saves operators/dispatchers significant time during restoration. Delayed automatic reclosing of the first terminal into a dead line seems risky.
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bacon4life
Electrical
For a normal reclose, I was curious because 30 seconds is longer than we use. Seems like the ideal reclose speed is faster that someone can get out of their vehicle after hitting a power pole.
By risky delayed reclosing, I was referring to:
By risky delayed reclosing, I was referring to:
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- #11
A 69 or 115kv line will be on a 100ft tower in a dedicated easement (in our case) making motor vechical collusion unlikely. But even then I know of 12.47 and 23kv reclosers that have a 90 second reclose sequence, or a non communicating automatic loop system where the tie recloser closes in 45 seconds after the source re-closer has done a 50 second 79 cycle.
But your point is far from invalid, a fast reclose is a good idea in those cases.
But your point is far from invalid, a fast reclose is a good idea in those cases.
davidbeach
Electrical
Most of our 57.5kV and 115kV is on the same poles as the underbuilt 13kV distribution; car hit pole is a definite problem. I'd love to have separate poles, but that just isn't going to happen, so if that's what you've got enjoy it.
SOTF - if the protection voltage is in front of the relay, aka on the line, then the SOTF trip elements must include non-directional overcurrent elements. If the protection voltage is behind the relay, SOTF can be done with just the zone 2 distance pickups. I see no reason not to include SOTF on transmission; distribution is sort of the opposite where instantaneous tripping is turned off following the first reclose. But on transmission there's no tapped fuses that you want to blow, so trip as quickly as possible and minimize the disturbance to the rest of the customers.
SOTF - if the protection voltage is in front of the relay, aka on the line, then the SOTF trip elements must include non-directional overcurrent elements. If the protection voltage is behind the relay, SOTF can be done with just the zone 2 distance pickups. I see no reason not to include SOTF on transmission; distribution is sort of the opposite where instantaneous tripping is turned off following the first reclose. But on transmission there's no tapped fuses that you want to blow, so trip as quickly as possible and minimize the disturbance to the rest of the customers.
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- #13
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- #14
Mbrooke,
For SOTF (or line test, as we call it) we use an overcurrent element AND'd with an undervoltage element.
The overcurrent element is typically set to be the smaller of 50% of the minimum TPF for the protected line, or 10A secondary.
We use 0.3pu for the undervoltage pickup, for more than 2 seconds.
Mark
For SOTF (or line test, as we call it) we use an overcurrent element AND'd with an undervoltage element.
The overcurrent element is typically set to be the smaller of 50% of the minimum TPF for the protected line, or 10A secondary.
We use 0.3pu for the undervoltage pickup, for more than 2 seconds.
Mark
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davidbeach
Electrical
Our SOTF trip always includes the zone 2 distance elements. If the voltage is behind the relay the distance elements will always work, even if you close into a set of grounds and the voltage goes to zero; the memory voltage polarization of the distance element will result in a trip. If the voltage comes from in front of the relay and you close into a set of grounds you won't get a distance trip; if the fault is further out the line you'll get enough voltage that everything turns on. With the voltage in front of the relay, the overcurrent elements have to deal with faults close enough that the distance elements can't but it's not necessary for the overcurrent to cover the whole line.
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- #18
I guess there is no way to get memory polarization with line VTs, if that is possible? Regarding the over current, I will probably go that route. In that case, what do you typically set this over current to or in relation to? Rules of thumb are fine as a starting point for my project.
Marks1080: Thank you- excellent! I never considered adding voltage to that over current, but I will take that into consideration.
Marks1080: Thank you- excellent! I never considered adding voltage to that over current, but I will take that into consideration.
davidbeach
Electrical
We start at 135% of the current for a remote bus fault. Generally that works, now and then it needs adjustment for one reason or another.
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