Transfer trip for breaker failure

[mbrooke]

Consider a bus fault with a simultaneous stuck breaker. Obviously zone 3 can take care of it, however the incident energy goes up astronomically. Does anyone know how to configure the line protection relays to transfer trip in such a case? Im rather lost on this one :dunce:

 

[Bugman1400]

Consider a bus fault with a simultaneous stuck breaker. Obviously zone 3 can take care of it, however the incident energy goes up astronomically. Does anyone know how to configure the line protection relays to transfer trip in such a case? Im rather lost on this one :dunce:

That only works if your line relays have comm over to the other side. If so, you can send a DTT. Otherwise, you are restricted to just the Zone 3 from the remote ends. However, your remote ends should see your local bus in a Zone 2.

 

[mbrooke]

That only works if your line relays have comm over to the other side. If so, you can send a DTT. Otherwise, you are restricted to just the Zone 3 from the remote ends. However, your remote ends should see your local bus in a Zone 2.

I have fiber optic communication since these relays (SEL) do line differential. But the question is how do I configure DTT or more precisely how do I get the relay to acknowledge that a buss differential relay has called for a trip and a breaker has become stuck?

Also, there is no harm in relying on zone2?

 

[Bugman1400]

I have fiber optic communication since these relays (SEL) do line differential. But the question is how do I configure DTT or more precisely how do I get the relay to acknowledge that a buss differential relay has called for a trip and a breaker has become stuck?

Also, there is no harm in relying on zone2?

Perhaps I'm getting a bit confused.....do you have line relays or diff relays? What SEL model#s do you have? Which relay is doing the breaker failure timing? Is it a separate relay or one of the line relays? If you have a line diff using a 311L or 411L, there are four 87L bits that you can use to xmit the BF DTT over to the other side. If you have a 321 or 421, then you can use mirrored bits to send the POTT and DTT signal over to the other side. Keep in mind that typical BF timing is around 10 to 12 cycles after the initial trip. So, this may add to the timing for the Incident Energy.

Zone 2 at the remote end will typically cover the local bus and is often used as backup protection in the event that the local bus diff scheme needs to be disabled. However, Zone 2 time is typically 20-30 cycles and is slower than a bus diff trip of 1 cycle. This may be a problem if the local bus is at a generation plant.

 

[mbrooke]

Perhaps I'm getting a bit confused.....do you have line relays or diff relays?

Line relays with differential protection. Step distance as backup. Inverse over current to protect the line from thermal damage should it be loaded above it LTE/STE.

What SEL model#s do you have?

SEL311L for single breaker bays and SEL411L for double breaker bays and M&T.

Which relay is doing the breaker failure timing?

Both primary and secondary relays (2x 311L or 2x411L)

Is it a separate relay or one of the line relays?

One of the line relays. I am abandoning my previous practice of having a separate breaker failure relay.

If you have a line diff using a 311L or 411L, there are four 87L bits that you can use to xmit the BF DTT over to the other side.

And this is easily programed and can be easily enabled via one of the inputs? My plan is to have the bus relay (SEL587Z) close a contractor that trips the breakers while energizing an input (or closing an output) on the SEL311L where the SEL311L stats its breaker failure sequence. If the SEL311L detects more than say 50amps for 8 cycle it will then send a DTT to the remote SEL311L to trip its breaker.

If you have a 321 or 421, then you can use mirrored bits to send the POTT and DTT signal over to the other side. Keep in mind that typical BF timing is around 10 to 12 cycles after the initial trip. So, this may add to the timing for the Incident Energy.

Confused here, can you elaborate? Im confused regarding mirrored bits.

My understanding is that when you integrate BF with the breaker failure relays the timing can be reduced.

Zone 2 at the remote end will typically cover the local bus and is often used as backup protection in the event that the local bus diff scheme needs to be disabled. However, Zone 2 time is typically 20-30 cycles and is slower than a bus diff trip of 1 cycle. This may be a problem if the local bus is at a generation plant.

True, but even in cases where the buss is far from any generation or stability prone areas I want to reduce the incident energy as much as possible. Zone 2 is considered a very, very last resort. All the stations have 2x buss relaying so even if one relay is out for service the other buss still provides the 2 cycle clearing time.

 

[Bugman1400]

And this is easily programed and can be easily enabled via one of the inputs? My plan is to have the bus relay (SEL587Z) close a contractor that trips the breakers while energizing an input (or closing an output) on the SEL311L where the SEL311L stats its breaker failure sequence. If the SEL311L detects more than say 50amps for 8 cycle it will then send a DTT to the remote SEL311L to trip its breaker.

Using an output of the 587Z into the input of your BF relay (311L) is typical as with any external BF relay. For the 311L, do a search in the relay manual for T1X or T1Y. These correspond to the 87L transmit bits. There are 4 for each 87L channel (T1X-T4X, T1Y-T4Y). These bits are transmitted over the Channel X or Channel Y of the comm that is used strictly for the diff scheme. If your scheme does not use both channels (some utilities only use one channel X or Y, not both) then those corresponding bits cannot be used. You can set one of these 87L bits to your BF DTT (ie T1X=SV09T where, SV09T is your timed-out BF). These bits also have the corresponding receive bits at the remote end (R1X-R4X, R1Y-R4Y). You can then tie the receive bit to your output which would then go to your 86 lockout (ie OUT201=R1X).

Confused here, can you elaborate? Im confused regarding mirrored bits.

Mirrored Bits (MB) can be used also. They are used in all 300 and 400-series SEL relays. Mirrored bit consist of 8 bits instead of 4 like the 311L/411L. The same principle applies but, instead of Channel X or Y, the comm channel will be from one of the relay RS-232 comm ports on the back of the relay. The MBs will be labeled as MBA or MBB and contain bits TMB1A-TMB8A or TMB1B-TMB8B.

My understanding is that when you integrate BF with the breaker failure relays the timing can be reduced.

In general, this may be true but, it depends on the relay. For example, the 300 series SEL relays have much slower processors. So, there may be some time saving advantages to using a 400 series relay even if the initiating relays are external.

True, but even in cases where the buss is far from any generation or stability prone areas I want to reduce the incident energy as much as possible. Zone 2 is considered a very, very last resort. All the stations have 2x buss relaying so even if one relay is out for service the other buss still provides the 2 cycle clearing time.

As I mentioned, Zone 2 typically has a 20 cycle delay, however, I've seen it shortened down to 15 cycles on a line protected by curr diff. In that case, you could potentially have a Zone 2 at the remote end beat out the BF relay at the local end.

 

[mbrooke]

Using an output of the 587Z into the input of your BF relay (311L) is typical as with any external BF relay. For the 311L, do a search in the relay manual for T1X or T1Y. These correspond to the 87L transmit bits. There are 4 for each 87L channel (T1X-T4X, T1Y-T4Y). These bits are transmitted over the Channel X or Channel Y of the comm that is used strictly for the diff scheme. If your scheme does not use both channels (some utilities only use one channel X or Y, not both) then those corresponding bits cannot be used. You can set one of these 87L bits to your BF DTT (ie T1X=SV09T where, SV09T is your timed-out BF). These bits also have the corresponding receive bits at the remote end (R1X-R4X, R1Y-R4Y). You can then tie the receive bit to your output which would then go to your 86 lockout (ie OUT201=R1X).




Mirrored Bits (MB) can be used also. They are used in all 300 and 400-series SEL relays. Mirrored bit consist of 8 bits instead of 4 like the 311L/411L. The same principle applies but, instead of Channel X or Y, the comm channel will be from one of the relay RS-232 comm ports on the back of the relay. The MBs will be labeled as MBA or MBB and contain bits TMB1A-TMB8A or TMB1B-TMB8B.



In general, this may be true but, it depends on the relay. For example, the 300 series SEL relays have much slower processors. So, there may be some time saving advantages to using a 400 series relay even if the initiating relays are external.


As I mentioned, Zone 2 typically has a 20 cycle delay, however, I've seen it shortened down to 15 cycles on a line protected by curr diff. In that case, you could potentially have a Zone 2 at the remote end beat out the BF relay at the local end.

Awesome Let me digest this and I will ask need be.

 

[mbrooke]

Using an output of the 587Z into the input of your BF relay (311L) is typical as with any external BF relay.

When you say input/output do you mean data port/fiber optic or 24 volt DC input? I can explain need be.

For the 311L, do a search in the relay manual for T1X or T1Y. These correspond to the 87L transmit bits. There are 4 for each 87L channel (T1X-T4X, T1Y-T4Y). These bits are transmitted over the Channel X or Channel Y of the comm that is used strictly for the diff scheme. If your scheme does not use both channels (some utilities only use one channel X or Y, not both) then those corresponding bits cannot be used.

I use both channels, but would this still work if one was inadvertently lost? And this is from 311L to 311L and not 587Z to 311L?

You can set one of these 87L bits to your BF DTT (ie T1X=SV09T where, SV09T is your timed-out BF). These bits also have the corresponding receive bits at the remote end (R1X-R4X, R1Y-R4Y). You can then tie the receive bit to your output which would then go to your 86 lockout (ie OUT201=R1X).

So the relay at the remote end will recognize a DTT and not display a differential trip?

Mirrored Bits (MB) can be used also. They are used in all 300 and 400-series SEL relays. Mirrored bit consist of 8 bits instead of 4 like the 311L/411L. The same principle applies but, instead of Channel X or Y, the comm channel will be from one of the relay RS-232 comm ports on the back of the relay. The MBs will be labeled as MBA or MBB and contain bits TMB1A-TMB8A or TMB1B-TMB8B.

Got, and makes sense.

In general, this may be true but, it depends on the relay. For example, the 300 series SEL relays have much slower processors. So, there may be some time saving advantages to using a 400 series relay even if the initiating relays are external.

Generally more critical applications call for multiple breakers per line (breaker and a half) so a 400 series relay is a given where faster clearing time also needs to take place.

As I mentioned, Zone 2 typically has a 20 cycle delay, however, I've seen it shortened down to 15 cycles on a line protected by curr diff. In that case, you could potentially have a Zone 2 at the remote end beat out the BF relay at the local end.

Perhaps. Im thinking the closing time of the input might determine that, unless you think I should use direct fiber optic/data signaling from the 587Z to the 311L?

 

[Bugman1400]

When you say input/output do you mean data port/fiber optic or 24 volt DC input? I can explain need be.

With a 587Z, it has to be hardwire since it doesn't support Mirrored Bit (MB). The other protocols supported by the 587Z serial ports are not adequate for BF initiation.

I use both channels, but would this still work if one was inadvertently lost? And this is from 311L to 311L and not 587Z to 311L?

Yes, you should OR the BF DTT signal at the remote end (ie DTT output=R1X OR R1Y).

So the relay at the remote end will recognize a DTT and not display a differential trip?

That is correct. The 87L bits are independent and can be used to do anything.


Got, and makes sense.


Generally more critical applications call for multiple breakers per line (breaker and a half) so a 400 series relay is a given where faster clearing time also needs to take place.

Perhaps. Im thinking the closing time of the input might determine that, unless you think I should use direct fiber optic/data signaling from the 587Z to the 311L?

As mentioned above, I don't think you can use FO on the serial port of the 587Z. I assumed your 587Z relay is in the same control house as your other relays and can be easily hardwired. If not, then you may need to use a SEL-2505 and FO into your BF relay. Typically 587Z relays are hardwired to an 86 bus lockout (86LO). You can take your BF Initiate (BFI) off of the 86LO or from the 587Z output. I prefer to do both if the 86LO does not have coil monitoring.

 

[mbrooke]

With a 587Z, it has to be hardwire since it doesn't support Mirrored Bit (MB). The other protocols supported by the 587Z serial ports are not adequate for BF initiation.

Awesome. Yes, this will be a 24 volt DC input into the 311L.

Yes, you should OR the BF DTT signal at the remote end (ie DTT output=R1X OR R1Y).




That is correct. The 87L bits are independent and can be used to do anything.


Got, and makes sense.


Generally more critical applications call for multiple breakers per line (breaker and a half) so a 400 series relay is a given where faster clearing time also needs to take place.

And the example you gave is initiating BF via a 24 volt hardwire input? (just double and triple checking).

As mentioned above, I don't think you can use FO on the serial port of the 587Z. I assumed your 587Z relay is in the same control house as your other relays and can be easily hardwired. If not, then you may need to use a SEL-2505 and FO into your BF relay. Typically 587Z relays are hardwired to an 86 bus lockout (86LO). You can take your BF Initiate (BFI) off of the 86LO or from the 587Z output. I prefer to do both if the 86LO does not have coil monitoring.

MY apologies, I gave the wrong impression. The 587Z is indeed within the same control hut as the 311Ls.

 

[mbrooke]

And oh, this is more on the side. But you would see nothing wrong in running this 24 volt BF initiate through a pair of isolating switches much like I do with CT, VT and trip signals?

 

[Bugman1400]

And oh, this is more on the side. But you would see nothing wrong in running this 24 volt BF initiate through a pair of isolating switches much like I do with CT, VT and trip signals?

It is typical to route the Trip or BFI signals through a set of test switches similar to PT and CT signals. This is for isolation and/or testing of a relay during commissioning, maintenance, or replacement. The test switches are usually clearly labeled to indicate a trip or BFI signal. Many times a red switch or red labeling is used.

 

[Bugman1400]

And the example you gave is initiating BF via a 24 volt hardwire input? (just double and triple checking).

I have never heard of 24 volts being used. In the utility industry, its usually 125VDC for transmission/distribution and 250VDC for generation plants. You should definitely make sure that all the devices involved are designed for 24 volts, if that is your voltage. I suppose 24 volts reduces the need for a full blown battery room.

 

[mbrooke]

It is typical to route the Trip or BFI signals through a set of test switches similar to PT and CT signals. This is for isolation and/or testing of a relay during commissioning, maintenance, or replacement. The test switches are usually clearly labeled to indicate a trip or BFI signal. Many times a red switch or red labeling is used.

Isn't red for VT and black for CT? I'm thinking a different color would be a better choice but unsure as to what.

 

[mbrooke]

I have never heard of 24 volts being used. In the utility industry, its usually 125VDC for transmission/distribution and 250VDC for generation plants. You should definitely make sure that all the devices involved are designed for 24 volts, if that is your voltage. I suppose 24 volts reduces the need for a full blown battery room.

Out of curiosity, aren't smaller substations and some switch gear not 24 volts?

 

[Bugman1400]

Isn't red for VT and black for CT? I'm thinking a different color would be a better choice but unsure as to what.

Typically, I've seen red used for trip signals. I think its more important to know which circuits trip a breaker or a lockout than it is to know the PT circuits. The CT circuits are always the easiest to identify because of the special test switches and the CT shorting terminal blocks.

As mentioned before, I've never seen 24 volt subs. For small subs, most utilities will use smaller 125VDC batteries (ie 25 to 100 aH). I've also seen NiCADs that have a smaller footprint than the Lead-acid but, they don't hold up in the heat. If the subs are too small then the devices will be AC trip instead of DC. In this case, there are no station batteries.

 

[mbrooke]

Typically, I've seen red used for trip signals. I think its more important to know which circuits trip a breaker or a lockout than it is to know the PT circuits. The CT circuits are always the easiest to identify because of the special test switches and the CT shorting terminal blocks.

I agree here. Though I like things organized by color Even got colored wire up to the relay :thumbsup:

As mentioned before, I've never seen 24 volt subs. For small subs, most utilities will use smaller 125VDC batteries (ie 25 to 100 aH). I've also seen NiCADs that have a smaller footprint than the Lead-acid but, they don't hold up in the heat. If the subs are too small then the devices will be AC trip instead of DC. In this case, there are no station batteries.

125 volts DC has on major disadvantage over 120 volts AC or 24 volts DC:

https://www.youtube.com/watch?v=Zez2r1RPpWY

 

[mbrooke]

As is why does SEL offer 12 and 24 volt relays and manufactures offer 12 and 24 volt trip coils?

 

[Bugman1400]

As is why does SEL offer 12 and 24 volt relays and manufactures offer 12 and 24 volt trip coils?

I think they offer the different models to meet the application and demand...not because they think its safer. There are some plants that I've seen that remove the fuses for the trip circuits and put in slugs instead. I think the principle is that many of the trip circuits may sit for years without being called upon. During this time, you can expect some type of oxidation or corrosion to set in. Its best to have a trip signal that has enough potential to make it through this oxidation and resistance to actuate the coil in the yard that may be some distance away. The less voltage you start out with, the less you have at the trip coil.

 

[mbrooke]

I think they offer the different models to meet the application and demand...not because they think its safer. There are some plants that I've seen that remove the fuses for the trip circuits and put in slugs instead. I think the principle is that many of the trip circuits may sit for years without being called upon. During this time, you can expect some type of oxidation or corrosion to set in. Its best to have a trip signal that has enough potential to make it through this oxidation and resistance to actuate the coil in the yard that may be some distance away. The less voltage you start out with, the less you have at the trip coil.

Correct, thats my point, demand. They would not make 12 and 24 volt relays if consumer were not looking for them. But in my case 24 volts is used in that its less likely to hold an arc at 125 volts. In a properly maintained system corrosion should not be an issue.