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Thread: CT reversed in bus differential zone

  1. #41
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    Quote Originally Posted by Bugman1400 View Post
    So what? With your way, what will clear for a fault in the bus coupler? Are you worried about tripping both buses for a fault on the aux bus. I think you'll have far more nuisance tripping during this crazy switching scheme and trying to follow unclear switching procedures. Just how many aux bus faults do you expect? Is the aux bus above or below the main bus?
    A fault in the coupler itself (internal breaker flash over) will be cleared via bus protection since in all cases my belief is the breaker will rest in the differential zone. My exact worry is tripping both busses for a fault on the aux bus- if I could have it so I could a fault on the aux bus does not clear the whole station I will be content.


    The Aux bus is next to the main buss (parallel strain bus rather than stacked) separated by a row of disconnects.
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  2. #42
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    Quote Originally Posted by mbrooke View Post
    A fault in the coupler itself (internal breaker flash over) will be cleared via bus protection since in all cases my belief is the breaker will rest in the differential zone. My exact worry is tripping both busses for a fault on the aux bus- if I could have it so I could a fault on the aux bus does not clear the whole station I will be content.


    The Aux bus is next to the main buss (parallel strain bus rather than stacked) separated by a row of disconnects.
    That is not a problem. Do some simulations. End of story.

  3. #43
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    Quote Originally Posted by topgone View Post
    That is not a problem. Do some simulations. End of story.


    What kind of simulations do you have in mind?
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  4. #44
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    Quote Originally Posted by topgone View Post
    That is not a problem. Do some simulations. End of story.
    Ok, picture it like this. Bus differential protection activates. How do I know which bus faulted? Having the coupler trip on an aux bus fault immediately tells me the aux bus is faulted, and if not then I know that can immediately be eliminated with attention turning to the main bus and bays.

    Edit: FWIW I will have CTs on both sides of the coupler. 587Z is at play for now. My apologies for not addressing it in this thread earlier.
    Last edited by mbrooke; 04-25-17 at 12:03 AM.
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  5. #45
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    Quote Originally Posted by mbrooke View Post
    Ok, picture it like this. Bus differential protection activates. How do I know which bus faulted? Having the coupler trip on an aux bus fault immediately tells me the aux bus is faulted, and if not then I know that can immediately be eliminated with attention turning to the main bus and bays.

    Edit: FWIW I will have CTs on both sides of the coupler. 587Z is at play for now. My apologies for not addressing it in this thread earlier.
    You need a curent injector(3-phase), a programmable logic software and some differential relays wired according to your protection scheme.
    To simulate, you would choose the expected fault current on the portion of the bus under investigation to inject and see if relays function as designed.

  6. #46
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    Quote Originally Posted by topgone View Post
    You need a curent injector(3-phase), a programmable logic software and some differential relays wired according to your protection scheme.
    To simulate, you would choose the expected fault current on the portion of the bus under investigation to inject and see if relays function as designed.

    Ok revised plan that does not involve any CT switch opening:


    Use a 487B, and have a selector switch on the mimick board that toggles the IN0XX contacts. Basically it would have 3 options: all bays on bus 1, all bays on bus 2, and zone 1 and zone 2 fused together for switching between them. This gives the required zones and does not include any switching of CT circuits.
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  7. #47
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    Quote Originally Posted by mbrooke View Post
    Ok, picture it like this. Bus differential protection activates. How do I know which bus faulted? Having the coupler trip on an aux bus fault immediately tells me the aux bus is faulted, and if not then I know that can immediately be eliminated with attention turning to the main bus and bays.

    Edit: FWIW I will have CTs on both sides of the coupler. 587Z is at play for now. My apologies for not addressing it in this thread earlier.
    if you are using partial 87b, you can tell which bus in faulted..


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  8. #48
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    Quote Originally Posted by rian0201 View Post
    if you are using partial 87b, you can tell which bus in faulted..


    Sent from my iPad using Tapatalk
    Might go that route then.
    What is esoteric knowledge today will be common knowledge tomorrow.

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