Dual bay relay for Main and Transfer

[mbrooke]

Ok, so this was suggested on another forum which was and is a life saver for me. However, I am still a bit puzzled on how to set the relay's settings. Should I just program both the line and transformer relays as a breaker and a half/ ring application (NUMBK=2 ESS=3 LINEI=COMB) and simply switch the through the CT switches or set the relays with the logic to consider this like a main/alternate type deal letting the relay choose to ignore or sum the input currents? The first approach is the simplest, however I am unsure if it would create any unforeseen problems.


From a PDF on applying such relays to M&T:

M&T as Dual Breaker

The relay settings allowed a certain level of CT selection control
NUMBK – the number of breakers in the scheme
o Ring, Breaker-and-a-half, M&T all use NUMBK = 2
ESS – the source selection
o Ring, Breaker-and-a-half use ESS = 3
o M&T uses ESS = Y
LINEI – Current for the protected line
o Ring, Breaker-and-a-half use LINEI = COMB
o M&T uses LINEI = IW, the breaker 1 (Normal Breaker) current
ALINEI – the alternate current source
o For Ring and Breaker-and-a-half this setting is unavailable
o For M&T ALINEI = IX, the breaker 2 (Bus Tie Breaker) current

 

[Bugman1400]

Ok, so this was suggested on another forum which was and is a life saver for me. However, I am still a bit puzzled on how to set the relay's settings. Should I just program both the line and transformer relays as a breaker and a half/ ring application (NUMBK=2 ESS=3 LINEI=COMB) and simply switch the through the CT switches or set the relays with the logic to consider this like a main/alternate type deal letting the relay choose to ignore or sum the input currents? The first approach is the simplest, however I am unsure if it would create any unforeseen problems.


From a PDF on applying such relays to M&T:

Need to see OL. Can PM if you wish.

 

[mbrooke]

Need to see OL. Can PM if you wish.

OL?

 

[Bugman1400]

OL?

Relay Oneline (OL)....typically shows the CTs, breakers, bus config, etc.

BTW, your PM mailbox is full and cannot accept replies.

 

[mbrooke]

Relay Oneline (OL)....typically shows the CTs, breakers, bus config, etc.

BTW, your PM mailbox is full and cannot accept replies.

Sorry, let me clean it up a bit.


Anyway, this is Main and transfer buss. Each element (line, transformer and capacitor) has the ability to go on the transfer bus fed fed by the transfer bus coupler breaker. Its a classic main and transfer out of an engineering book, nothing special.

 

[mbrooke]

These two papers explain what I am trying to do:



https://conferences.wsu.edu/forms/wprc/2014/Papers/bea2_pap.pdf


https://conferences.wsu.edu/forms/wprc/2014/Presentations/bea2_ppt.pdf


Basically I have always relayed M&T by using a single input CT input relay and manually switching the CT and trip circuit or in a few cases individual relays for the bus coupler breaker. Both have serious draw backs and are the worst (if not impossible) with line differential protection. This is the first time I am taking a dual breaker relay mad for ring, breaker and a half and double breaker double being applied to M&T.

 

[Bugman1400]

These two papers explain what I am trying to do:



https://conferences.wsu.edu/forms/wprc/2014/Papers/bea2_pap.pdf


https://conferences.wsu.edu/forms/wprc/2014/Presentations/bea2_ppt.pdf


Basically I have always relayed M&T by using a single input CT input relay and manually switching the CT and trip circuit or in a few cases individual relays for the bus coupler breaker. Both have serious draw backs and are the worst (if not impossible) with line differential protection. This is the first time I am taking a dual breaker relay mad for ring, breaker and a half and double breaker double being applied to M&T.

The xfer breaker should have its own CTs and line relay and would typically cover the xfer bus and the switched load. I've always had the settings for the normal line relay as a Group X setting in the xfer relay. If your line has a line diff and your xfer relay does not have that option then you'll have to disable the diff scheme and rely on backup distance and OC protection. Typically, the xfer breaker is used for temp configs anyways. This approach effectively cuts loose the normal relay and its panel for upgrades, maintenance or whatever.

If your xfer breaker does not have its own relay then perhaps you can wire the xfer bkr CTs to IX of the normal relay. For Group 2 setting group, you can set ESS=Y and configure the rest like you want instead of trying to match the table in the manual. Set LINEI=COMB and NUMBK=2 as you suggested. The LINEI is for the protection; as long as there are no stray currents from the normal breaker then you should be good. This should also cover you while the xfer is being made between the two breakers. You'll also need to set up the I/O to trip and reclose the xfer breaker. This will also need to be set up in the reclose logic as well. Since the xfer breaker will be Bkr 2, you can set it up as the LEAD bkr instead of Bkr 1.

 

[mbrooke]

The xfer breaker should have its own CTs and line relay and would typically cover the xfer bus and the switched load.

What is better about a dedicated relay?

I've always had the settings for the normal line relay as a Group X setting in the xfer relay. If your line has a line diff and your xfer relay does not have that option then you'll have to disable the diff scheme and rely on backup distance and OC protection. Typically, the xfer breaker is used for temp configs anyways. This approach effectively cuts loose the normal relay and its panel for upgrades, maintenance or whatever.

Exactly just some if the issues I am trying to avoid. How many settings can such a relay store anyways?

If your xfer breaker does not have its own relay then perhaps you can wire the xfer bkr CTs to IX of the normal relay. For Group 2 setting group, you can set ESS=Y and configure the rest like you want instead of trying to match the table in the manual. Set LINEI=COMB and NUMBK=2 as you suggested. The LINEI is for the protection; as long as there are no stray currents from the normal breaker then you should be good. This should also cover you while the xfer is being made between the two breakers. You'll also need to set up the I/O to trip and reclose the xfer breaker. This will also need to be set up in the reclose logic as well. Since the xfer breaker will be Bkr 2, you can set it up as the LEAD bkr instead of Bkr 1.

The whole goal is to eliminate the separate relays for the transfer breaker and have each bay relay with the capability to control the transfer breaker.

In regards to relcosing, breaker 1 (normal) will lead, so will the relay see any issue on transfer when the BR1 does not reclose?

 

[Bugman1400]

What is better about a dedicated relay?

For example, if you have 4 normal circuits then you can just program the xfer bkr relay with Group settings that are a direct copy of the normal relay.I see this application mostly for radial loads. It may be more difficult for line diffs; you would need to switch the comm ckt.

Exactly just some if the issues I am trying to avoid. How many settings can such a relay store anyways?

Most SEL relays have 6 setting groups.

The whole goal is to eliminate the separate relays for the transfer breaker and have each bay relay with the capability to control the transfer breaker.

Ok, I understand the goal of some utilities to save cost but, it usually aggravates the linemen and sub techs when they have to troubleshoot or take outages.

In regards to relcosing, breaker 1 (normal) will lead, so will the relay see any issue on transfer when the BR1 does not reclose?

If you are using a 400-series SEL relay, you can usually set up a LEAD breaker and a FOLLOWER breaker. The relay doesn't care which is the LEAD but, you'll need to ensure that the reclosing and other logic is set up to use this feature. I can send you some of the default logic that I use for this but, you'll need to receive PMs.

 

[mbrooke]

For example, if you have 4 normal circuits then you can just program the xfer bkr relay with Group settings that are a direct copy of the normal relay.I see this application mostly for radial loads. It may be more difficult for line diffs; you would need to switch the comm ckt.

No, not radial. transmission and the transformers require differential. BTw, how do you change these settings in your application?

Most SEL relays have 6 setting groups.

Good to know.

Ok, I understand the goal of some utilities to save cost but, it usually aggravates the linemen and sub techs when they have to troubleshoot or take outages.

I disagree here. Having to switch CT circuits or selecting the correct settings for the bus tie is far more complicated and far more likely to lead to user error. Considering this application calls for Caps, transformers and different lines on the bus tie at minimum you would need 3 different, dedicated relays, or more precisely 6 for primary and backup protection just for the bus tie. You will also need a fiber optic switcher to keep line differential in place. This adds far more cost and outside of 15 and 25kv distribution is rare.


However, by having any normal bay relay have the ability to take control of the bus tie without any CT switching and no momentary outages of protection greatly improves maintenance, reliability and upfront cost on all levels.

If you are using a 400-series SEL relay, you can usually set up a LEAD breaker and a FOLLOWER breaker. The relay doesn't care which is the LEAD but, you'll need to ensure that the reclosing and other logic is set up to use this feature. I can send you some of the default logic that I use for this but, you'll need to receive PMs.

I cleaned out my PMs and I am all open. Let me know if it will go through