Voltage Balance Relay / Switching VT inputs

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mbrooke

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Does any have a general wiring diagram of a voltage balance relay application used to switch CVT circuits feeding protection relays? Or is there another recommended way to do it?


In simple terms I want to be able to switch AC relay voltage between bus potential transformers.
 

iceworm

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I've only seen one - it was a decrepit GE, probably 20 years old when I saw it 40 years ago. As I recall, it was wired to block certain protective relays, not switch to another set of PTs.

No reason why you couldn't though.

I've seen pictures of a Basler. But, I'm sure you have tried a search on a Basler 1-60.

I'm not much help, but I am interested in the application - as in, what is the issue requiring a solution?
 

mbrooke

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I've only seen one - it was a decrepit GE, probably 20 years old when I saw it 40 years ago. As I recall, it was wired to block certain protective relays, not switch to another set of PTs.

No reason why you couldn't though.

I've seen pictures of a Basler. But, I'm sure you have tried a search on a Basler 1-60.

I'm not much help, but I am interested in the application - as in, what is the issue requiring a solution?



One bay that can connect to two bus bars. I'd like it so one bus can be removed from service while still having 21 and 67 elements in service.
 

iceworm

Curmudgeon still using printed IEEE Color Books
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North of the 65 parallel
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EE (Field - as little design as possible)
One bay that can connect to two bus bars. I'd like it so one bus can be removed from service while still having 21 and 67 elements in service.
I'm out of my element, but still curious: I'm sure you considered a metering switch. Electroswitch likely makes one just for that.
 

Russs57

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Yes, I'm probably even more out of my element. Still curious though. Don't know what you mean by "21 and 67 elements".

Everyone of these relays I have come across were associated with generators. There intent was usually to prevent over excitation of generator in the event of a PT fuse failure (but then I'm guessing you already know that).
 

mbrooke

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Yes, I'm probably even more out of my element. Still curious though. Don't know what you mean by "21 and 67 elements".

21 is ANSI for step distance protection

67 is ANSI for directional over current.

Both 21 and 67 require a 3 phase voltage input to work which in this cases comes from the bus. The line terminal has only one VT on phase A, and this is simply for checking sync before re-closing the line.


Basically, if the North bus needs to be taken out of service and a bay is now on the south bus, I'd also like to have the south bus's VTs now deeding the relay and visa versa.



Everyone of these relays I have come across were associated with generators. There intent was usually to prevent over excitation of generator in the event of a PT fuse failure (but then I'm guessing you already know that).


Correct, that is typically where you find them. In this case though I am thinking outside the box a bit.
 

Russs57

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Okay, dumb question number 101. Wouldn't both the south and north bus have their own dedicated (21 and 67) protection relays?

While I am sure it could be made to work with the right addition of associated relays it strikes me the the voltage balance relay is tasked with "inhibiting" something whereas you are trying to "enable" something.

I'm an electro-mechanical relay type of guy. I trust them, understand them, and know how to work around their failure. These days I highly suspect the functions you desire are usually micro-processor based.

Now keep in mind I know nothing of high voltage distribution networks (and am posting more to gain knowledge and help myself than you I must admit). Still, out of the mouth of babes and all:)
 

mbrooke

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Okay, dumb question number 101. Wouldn't both the south and north bus have their own dedicated (21 and 67) protection relays?

While I am sure it could be made to work with the right addition of associated relays it strikes me the the voltage balance relay is tasked with "inhibiting" something whereas you are trying to "enable" something.

I'm an electro-mechanical relay type of guy. I trust them, understand them, and know how to work around their failure. These days I highly suspect the functions you desire are usually micro-processor based.

Now keep in mind I know nothing of high voltage distribution networks (and am posting more to gain knowledge and help myself than you I must admit). Still, out of the mouth of babes and all:)



You only have one breaker per terminal (except the auto transformer bay, but ignore that) and at any time only one bus is connected to any one breaker. Each breaker has its own set of CTs. The CTs, close command, trip command and 1 phase sync VT all connect to one microprocessor relay or one set of EM relays. The voltage needed for 21 and 67 come from either bus, and is switched (selected) before going to the single relay.


Bus bar protection is its own beast. Usually one SEL 487B for 7 terminals or 3 (one per phase) for up to 21 terminals.


BTW, ask away. I am willing to teach you everything I know. :) And I think it will go the other way around too as I have a very limited understanding of EM relays.
 

Phil Corso

Senior Member
MBrooke...

My interpretation of your requirement is that you want to transfer the Generator's (or Transmission-line's) Relay '21' to the 115-kV bus its connected to!

If my recollection is correct, then, yes, the Basler or GE 1-60 will work! However, you may need to alter the blocking/permissive-logic that is available !

Regards, Phil Corso
 

mbrooke

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MBrooke...

My interpretation of your requirement is that you want to transfer the Generator's (or Transmission-line's) Relay '21' to the 115-kV bus its connected to!

If my recollection is correct, then, yes, the Basler or GE 1-60 will work! However, you may need to alter the blocking/permissive-logic that is available !

Regards, Phil Corso


What are your recommendations for LOP?
 

Phil Corso

Senior Member
MBrooke…

I’ve interpreted your quest to consist of two parts: a) one related to ANSI ‘60’ or LoP, i.e., loss of VT power (due to inadvertent operation of its primary or secondary (if any) fuses); and b) alignment of the bus-source related to the line’s ANSI ‘21’ and ‘67’ functions!

Starting with a) the LoP:
It is used when there are two sets of VT’s on the same-circuit or bus! It certainly can be used with the 2 sets of VT’s associated with N-bus and S-bus! Synchronicity is not essential because only voltage-magnitudes are monitored and compared, not their relative vector displacement!

And now b) Alignment
It is obvious that the ‘21’ and ‘67’ relays must be connected to the same circuit in which current-flows! This can be done easily, using position of the bus-selector switches and very simple ATC’s!

Example
As an example, consider Line N9803. If Switch N9801 is closed, then connect the required phase-voltages to N-bus VT’s! Conversely, if Switch N9802 is closed, then connect the required phase-voltages to S-bus VT’s!

I hope this helps! Phil
 

mbrooke

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Technician
MBrooke…

I’ve interpreted your quest to consist of two parts: a) one related to ANSI ‘60’ or LoP, i.e., loss of VT power (due to inadvertent operation of its primary or secondary (if any) fuses); and b) alignment of the bus-source related to the line’s ANSI ‘21’ and ‘67’ functions!

Spot on!

Starting with a) the LoP:
It is used when there are two sets of VT’s on the same-circuit or bus! It certainly can be used with the 2 sets of VT’s associated with N-bus and S-bus! Synchronicity is not essential because only voltage-magnitudes are monitored and compared, not their relative vector displacement!

And now b) Alignment
It is obvious that the ‘21’ and ‘67’ relays must be connected to the same circuit in which current-flows! This can be done easily, using position of the bus-selector switches and very simple ATC’s!


Even better then- I like the idea of bus-selector switches.

As an example, consider Line N9803. If Switch N9801 is closed, then connect the required phase-voltages to N-bus VT’s! Conversely, if Switch N9802 is closed, then connect the required phase-voltages to S-bus VT’s!

I hope this helps! Phil

Ok. But- should I use the isolator aux contacts (N9801/N9802) to do the switching or have a simple rotary switch by the relay for selecting it manually? I know I'm splitting hairs on this one.
 

Phil Corso

Senior Member
MBrooke...

I'm against a manual-override in this situation. Think more about the inherent-logic available in mechanically-interlocked devices such as an ATC, ATS, or even a reversing motor controller!

Phil
 
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