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Relcosing logic for 311C

Relcosing logic for 311C

(OP)
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.

RE: Relcosing logic for 311C

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.

RE: Relcosing logic for 311C

(OP)

Quote (David Beach)

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.


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.


Quote:

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.


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?


Quote:

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.

Makes sense and I will keep this in mind.

RE: Relcosing logic for 311C

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.

RE: Relcosing logic for 311C

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.

RE: Relcosing logic for 311C

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.

RE: Relcosing logic for 311C

(OP)
30 seconds is just a number that was deemed quick yet long enough to allow anything (everything) out on the line that could be temporary to clear. Why would 30 seconds be risky?

RE: Relcosing logic for 311C

30 seconds is what we used for 'long-time cancel' of reclose. Which basically means if a reclose was called for, but nothing happens (due to logic) for 30 seconds, the reclose system is reset.

RE: Relcosing logic for 311C

(OP)
For me 79 reset is about 90 seconds after a successful reclose.

@Cranky108, I use SOTF even on bus mounted VTs in that a 3 phase fault near the substation can also produce deeply depressed voltages.

RE: Relcosing logic for 311C

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:

Quote (having it so the relay will automatically come back in once the line is energized say several hours latter after repair? )


RE: Relcosing logic for 311C

(OP)
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.

RE: Relcosing logic for 311C

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.

RE: Relcosing logic for 311C

(OP)

Quote (David Beach)

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.

None of that here over 35kv, but in such a case it would certainly make sense and I hear you.


Quote:

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.

Any idea what these typical over current values should be set at? Would there be an flaws using zone 2 for line VTs?

RE: Relcosing logic for 311C

(OP)
If SOTF is off for either case, won't a 3 phase fault in front of the line result in the relay never opening because nothing can "polarize" the MHO?

RE: Relcosing logic for 311C

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

RE: Relcosing logic for 311C

I believe there are some setting limits for SOTF for lines that are part of the BES in North America.

RE: Relcosing logic for 311C

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.

RE: Relcosing logic for 311C

(OP)
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.

RE: Relcosing logic for 311C

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.

RE: Relcosing logic for 311C

(OP)
Sounds reasonable. Is it definite time or inverse time for you guys?

RE: Relcosing logic for 311C

Definite time.

RE: Relcosing logic for 311C

I think davidbeach's setting of 135% works better with the zone 2 supervision he uses.

If you are using OC only (with voltage supervision - which I would recommend) that pickup will be too high.

50% minimum TPH fault is a good level to use (or 10A secondary - whichever is less) for OC line test. You want to consider the system configuration for when you actually want line-test to work. The line is dead, and one terminal gets closed in first. That's the line test scenario. You could be testing because someone left grounds on the line (maybe the most common reason for this), but also consider other types of possible faults that could happen while a line is dead.

I believe our standard voltage setting for supervision of the OC element is 0.3 pu, probably based on a 500kV application. You may want to tweak that depending on your set-up, but I think 0.3 should be safe for most applications.

RE: Relcosing logic for 311C

(OP)
Is it possible the setting is higher to take tapped loads into account? What would happen if I choose not to have voltage supervision (in general of course)?

RE: Relcosing logic for 311C

How much higher are you talking about? SOTF phase over current is usually set above 150% of the line 4 hour rating.

If you are expecting unbalanced loading, then setting the ground higher is alright.

RE: Relcosing logic for 311C

(OP)
@cranky108, I think that sounds more right- I think. I will let Mr. Beach explain though.

RE: Relcosing logic for 311C

Not being one of those admitted to the inscrutable world of protection scheme jargon, I searched both here in Eng-Tips and on line generally for what SOTF means, and the only answer I've received so far is Survival of the Fittest; it must be a jungle out there...

So: I apologize for my ignorance, but what is SOTF an abbreviation for in the Protection and Control world?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Relcosing logic for 311C

Switch onto fault

RE: Relcosing logic for 311C

Thx!

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Relcosing logic for 311C

(OP)
Switch on to fault. The POCO world has some odd terms out there! :P

RE: Relcosing logic for 311C

We refer to SOTF as 'Line-Test'...

but what is "POCO" ????

RE: Relcosing logic for 311C

(OP)
POCO= Power company

Sorry for all the jargon. I tend to over use it at times lol.

RE: Relcosing logic for 311C

SOTF is a feature in the relays that activates selected elements while the breaker is open and for the first while after the breaker is closed. We typically use a 30 cycle SOTF time, so for the first 30 cycles following breaker close the zone 2 distance elements and any included overcurrents will trip instantaneously. Once the 30 cycle timer expires the SOTF tripping equation is ignored.

RE: Relcosing logic for 311C

Hi marks1080, our utility also uses the term Line Test Protection, hence my befuddlement by "SOTF," a term I had never encountered before.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Relcosing logic for 311C

SOTF is used in some relay manuals, and in NERC documents, hence the reason we use that term.

RE: Relcosing logic for 311C

And my utility joined NERC relatively recently...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Relcosing logic for 311C

I guess I should say, welcome to hell. Or almost hell.

The issue is not that most of the requirements are a concern, it's the paperwork and documentation, that required us to hire so many lawyers who don't even understand the requirements.
Also the auditors who have no idea what they are auditing. They just want to see the paperwork.

It's sort of like a federal government takeover of the utilities.

RE: Relcosing logic for 311C

Except that NERC is a North American "multinational" organization, which explains how my utility, which is Canadian, can be a member.

I am wondering: are there any US/Mexico tie lines that will need to be routed through a "power wall" in some manner? bigsmile

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Relcosing logic for 311C

(OP)
@Cranky, I agree, and the gov should not be trying to take control of the private sector- especially what it knows little about.

Regardless what people think, places like India are where talent can spread its wings.

RE: Relcosing logic for 311C

I really don't want to move to india, as I might be the tallest person around.

There are lines into Baja Mexico, likely they are taller than the wall of Southern Cal/Mexico border.

RE: Relcosing logic for 311C

(OP)
You will fall in love with their power engineering culture- and there substations too. They grow flowers in them. thumbsup2


But with the way things are going we might not even be exchanging power with Mexico.

RE: Relcosing logic for 311C

I also hear they have problems with people stealing PCB oil, because they hear it is good for their skin.

The connections with Mexico are not that major, in that it only includes Baja Mexico, and not the whole country.
I was not even aware they use 60 Hz until a number of years ago.

RE: Relcosing logic for 311C

(OP)
At least they aren't frying with it lol.

If I am not mistaken Mexico used to be 50Hz more than half a century ago but was converted over, at least that is what I have heard.

RE: Relcosing logic for 311C

Interesting enough Peru is 60 Hz.

RE: Relcosing logic for 311C

(OP)
Is is, and then abruptly changes to 50Hz south of Brazil. Jamaica is 50Hz when you would think it would be 60Hz.

https://www.youtube.com/watch?v=RV3hEKLNm74

Although to be honest I prefer the sound of 50Hz to 60Hz.

RE: Relcosing logic for 311C

(OP)
This might be for a new thread- but want to re-use this one since its along the same lines.

Does anyone know how to set the logic such that re-closing is blocked for zone 2 and zone 3 faults but proceeds as normal for a zone 1? This would hold for both positive sequence MHO and ground quad elements in regard to their respective zones.


I checked the manual but it only mentions 3 phase faults as follows:


Quote:

Blocking reclose on three-phase faults. Relay Word bits MPPn
(Zone/Level n phase-to-phase compensator distance element)
and MABCn (Zone/Level n three-phase compensator distance
element) may be used to discriminate between phase-to-phase
and three-phase faults in the SELOGIC® control equation
79DTL (drive-to-lockout).

79DTL = MABC2 * !MPP2 …


RE: Relcosing logic for 311C

I've no idea why you'd want to do that, but it would be really easy.

First set the zone 1 common timer to 0, not OFF. Then 79DTL would be TRIP * !Z1T.

I've seen too many instances where relays over trip for what ever reason to not want every distance element trip to reclose. But this is far from the first time I've seen the idea of only reclosing on zone 1, so maybe I'm missing out on something.

What about faults toward the remote end of the line for which zone 1 never picked up? How well do all of your zone 3 (probably really zone 4 if you're using SEL relays) elements coordinate? That is, how well do they continue to coordinate as tripping progresses? What looks to coordinate before the first trip may not, or conversely, what looks not to coordinate at all prior to the first trip actually coordinates perfectly well afterward. Personally, I'd be more worried about not getting the reclose on an over trip than having a zone 4 operate twice.

RE: Relcosing logic for 311C

(OP)

Quote (David Beach)

I've no idea why you'd want to do that, but it would be really easy.

First set the zone 1 common timer to 0, not OFF. Then 79DTL would be TRIP * !Z1T.

Oh, that is easy! :)

Quote:

I've seen too many instances where relays over trip for what ever reason to not want every distance element trip to reclose. But this is far from the first time I've seen the idea of only reclosing on zone 1, so maybe I'm missing out on something.


In a system with none communicating protection relays a Zone 2 pickup can either be a line fault on the far end or a bus fault with a simultaneous stuck breaker at the receiving station. If the latter it is generally a good idea not to reclose onto a faulted bus. Now with communicating relays a failed breaker during a bus fault can send over a DTT to the sending station preventing a re-close. In such a system (with communication) relcosing one both zone 1 and zone 2 can be done without worry.

I am sure there are other reasons out there, but in my case this is the primary driver not to reclose on zone 2.


Quote:

What about faults toward the remote end of the line for which zone 1 never picked up?

In such a system both 311C (or both 421) relays have a single re-close enabled on Zone 1. Which ever relay picked up zone 1 will reclose 15 or 30 seconds latter, and if the re-close is successful the relay on the other end which picked up on zone 2 will re-close after a synch check (hot line, hot bus). If both ends pickup on zone 1, then one end will reclose after 15 seconds and then the other after 30 seconds regardless if the first relay was successful or not at re-closing.

I know this sounds messy, but in a none communicating system its often a compromise.



Quote:

How well do all of your zone 3 (probably really zone 4 if you're using SEL relays) elements coordinate? That is, how well do they continue to coordinate as tripping progresses? What looks to coordinate before the first trip may not, or conversely, what looks not to coordinate at all prior to the first trip actually coordinates perfectly well afterward. Personally, I'd be more worried about not getting the reclose on an over trip than having a zone 4 operate twice.

In my world if a a relay trips on zone 3 (zone 4) this would indicate a serious problem such failed relaying at a remote substation. There of course could be a high Z fault out on the line, but the concern is generally not great enough to consider reclose.

Of course zone 3 trips can occur if a line is heavily loaded, however this would be mitigated via load shedding or generation re-dispatch before zone 3 elements (or over current elements) pick up.

Generally speaking a system which can tolerate a 30 second reclose delay via 3 pole tripping (vs needing single pole high speed auto reclosing) indicates a strong system with many other paths in the flow-gate. Thus biasing a system for dependability rather than security presents no major risk to losing load and is considered good practice. A line or element failing to trip, or a bus fault reclose, take more concern.

Though I do hear you, and your concerns are valid none the less.


RE: Relcosing logic for 311C

Quote (mbrooke)

In such a system both 311C (or both 421) relays have a single re-close enabled on Zone 1. Which ever relay picked up zone 1 will reclose 15 or 30 seconds latter, and if the re-close is successful the relay on the other end which picked up on zone 2 will re-close after a synch check (hot line, hot bus). If both ends pickup on zone 1, then one end will reclose after 15 seconds and then the other after 30 seconds regardless if the first relay was successful or not at re-closing.
In that case my very simple equation won't do what you want. What you'll need is something in the reclose supervision equations that will allow a reclose into a dead line following a zone 1 trip but then require the line to come hot prior to allowing a reclose for any other trip. That probably takes a logic variable or two so that you get the right conditions.

RE: Relcosing logic for 311C

(OP)
Any idea what the equation ought to look like?

RE: Relcosing logic for 311C

Just an idea that we use: 79DTL=.. +M2AB*M2BC*M2CA (or something like that) to prevent reclosing on three phase faults.

RE: Relcosing logic for 311C

(OP)
Thanks, will use that when the opportunity comes up.

A hypothetical what if... does not mean I will do it that way. What if I just kept things close to the factory settings so the speak, giving both relays a single reclose attempt (15 sec for one 30 for the other) and not bothering to to stop reclose on zone 2 and zone 3?

RE: Relcosing logic for 311C

If you're doing the 15 & 30 routine, you could have the 15 sec end close regardless and have the 30 second end only close into a hot line. That makes things relatively simple. But why 30 seconds? If one end closes at 15 seconds and holds for even a couple of seconds it's probably going to hold for 30 seconds; where we have different speeds, and the slow end only closing to a hot line, we wait a whole 30 cycles between the first close (will trip instantaneously on SOTF if the fault is still there) and the "slow" end closing.

RE: Relcosing logic for 311C

(OP)
Just values that feel "right" I guess, and in the event the fault is of such type that it does not flash over immediately. There are some fault (which involve tree branches for example) where the branch across the line will steam, flash-over, and then steam again for a few seconds after reclose before flashing over into an arc. The idea is to make sure the line will truly hold, and that all elements be it zero /negative sequence inverse time over current and impedance elements have a chance to pickup.

Here is one example of steaming before flashing over:


https://www.youtube.com/watch?v=pNsUDmlG6js

RE: Relcosing logic for 311C

(OP)
Thank you for the PDF :)


Still a tad confused though- I am able to get zone 2 and zone 3 to initiate drive-to-lockout, however is there anyway to set up an timed 79DTL expiration or reset for when the line comes back live?

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