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Commentator

Join Date: May 2011
Posts: 84
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What is gaurd relay ?

06/16/2011 2:46 PM

One installed in our panel is ABB RXP8. Can any one tell me what is gaurd realy and what is it's function ?

I could not find the details even in google or ABB website.

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Guru

Join Date: Apr 2009
Location: USA, Florida
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#1

Re: What is gaurd relay ?

06/16/2011 3:00 PM

It is for system protection. It is basically used in a "linefinder" circuit to make sure only one linefinder is connected to a circuit when multiple relays operate.

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Commentator

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#2
In reply to #1

Re: What is gaurd relay ?

06/16/2011 8:51 PM

can you plz elaborate more on this.. i could not get you.. is there any link from which you can share the information ?

Thanks for the reply :)

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Guru

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#3
In reply to #2

Re: What is gaurd relay ?

06/17/2011 9:38 AM

Try this as an example. You should have something similar in your equipment manual.

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#4

Re: What is gaurd relay ?

06/17/2011 11:24 AM

A guard relay is usually used in a permissive trip scheme to protect against loss of the communications channel. A guard signal is transmitted continually from the remote terminal. It verifies that the communication channel is valid. Then, when a trip signal is sent, if there is a guard signal, the trip is considered good and is permitted to actually trip the circuit breaker. If the guard is not there, then the trip signal is considered spurious, and not treated as valid.

Check out the following link for GE's "Art & Science of Protective Relaying" free download, and look at Chapter 5 on pilot-wire relaying.

http://www.gedigitalenergy.com/multilin/notes/artsci/index.htm

Your ABB relay is probably just an auxiliary relay used in the pilot scheme to provide some function related to the pilot wire "guard," such as enabling or blocking another relay's operation

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Commentator

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#5
In reply to #4

Re: What is gaurd relay ?

06/17/2011 12:57 PM

well we have this auxilliary relay in our synchronization panel where we synchronize our generators with grid or vice versa. The command for pick up of this aux relay comes from synchro check relay which is spau 140c (abb make). Question is why only this relay type rxp8 (called guard relay as per our drawings) and not any other aux relay.? many thanks for valuable links and suggestions. :)

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#6
In reply to #5

Re: What is gaurd relay ?

06/17/2011 1:39 PM

Why "only" this type of relay? You have to ask the panel manufacturer that question, but it's probably because he likes to use ABB relays and they are available to meet his requirements. Without seeing a relay schematic, I can't tell you any more about the specific function of the relay. Why don't you ask the manufacturer? We can't read minds.

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#7

Re: What is gaurd relay ?

07/11/2020 2:39 PM

If it is in ECP panel and being used for sync than it should be named 25-G which is used in synchronizing of generators. What this relay basically does is that if sync permissive relay 25X is not picked means synchronizing condition is not met and we give closing command to the breaker than it will pick up and will block the command.

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#8

Re: What is gaurd relay ?

07/11/2020 4:25 PM

I believe this is a test relay for testing your protection circuits the easy way....

..."A test switch may be used where testing relays or instruments would otherwise require manual disconnection and shorting of the instrument transformer’s secondary or control wiring. It may also well be used in the testing of complete relay systems, even when each individual relay has its own test switch. A test switch can also be used for other testing needs not directly associated with relays, such as for switchboards or voltmeters."...

https://www.hitachiabb-powergrids.com/offering/product-and-system/substation-automation--protection---control/products/protection-and-control/combiflex-modular-relays-and-accessories/test-equipment/rtxp

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#9

Re: What is gaurd relay ?

02/23/2022 11:06 AM

Yes. The panel manufacturer can. Telephone?

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