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Anonymous Poster #1

Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 3:31 AM

One of my projects which I am currently working on has 2 interconnected switchgears with 2 mains and 6 tie breakers. This is the first time I have come across such a complex switchgear arrangement and I need help in getting some information on ground fault protection looping.

Switchgear-1,

Main1-4000A

Tie1 -4000A

Tie2 -4000A

Tie3 -3200A

Feeders in between Main-1 and Tie-1.

Tie -1 and 2 are in series without any feeders in between.

feeders in between Tie 2 and tie 3

Switchgear-2,

Main2-4000A

Tie1 -4000A

Tie2 -4000A

Tie3 -3200A

Feeders in between Main-2 and Tie-1.

Tie -1 and 2 are in series without any feeders in between.

feeders in between Tie 2 and tie 3

The Gears are 4Wire 480V Job required with Ground Fault protection.

Since we don't have a new design right now, I have used a design with reference from Multisource Ground Fault Looping using Summation CTs for Main Tie Tie Main Scheme.

Basically, all of the summation CTs on the ties are wired directly in series with each other.

But there is a problem. Due to any of the open Tie Breakers, at least a couple of the summation CTs will not see the fault and resist current flow in the remaining CTs.

Also I have not used Auxiliary CTs in this arrangement for the above consideration.

Can you please help me out in getting information on such Switchgear Arrangement?

I will share hand sketch of the design once I get ample information.

If any other information is required, please write it in the comment section.

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#1

Re: Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 3:52 AM

It is astonishing that, on the basis that the question has been asked here, there is no-one else at the facility that can answer these sorts of questions. Having a mentor, or several of them, is an essential part of any young Engineer's career path.

Design procedures involve having "second person check" and "approved for construction" signatories to validate design documents ready for issue. One thing that CR4 cannot do is provide signatures for those boxes in the design documents!

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Anonymous Poster #1
#2
In reply to #1

Re: Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 4:03 AM

There are quite a few in the facility who have gone through the circuits but they are not yet fully convinced about their answers as this is their first time with such a complex circuit. They are looking for some research on it and so am i.

i just need some information on the subject. i am not asking anyone to do the design.

i am just here to learn and i dont want any Signatures claiming accountability.

I am sure there are quite a few engineers who are familiar with this subject. All i ask is information.

thank you for your time

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25917
Good Answers: 683
#3
In reply to #2

Re: Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 4:07 AM

Then maybe it's time for all those individuals to get their heads together in one place at one time. Do join in, and do let the forum know how the problem was solved.

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Join Date: Mar 2011
Location: Lubbock, Texas
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#4

Re: Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 8:51 AM

Your predecessor there was not named coolyaar was he?

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Anonymous Poster #2
#5

Re: Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 11:04 AM

welcome to cr4

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#6

Re: Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 12:52 PM
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#7
In reply to #6

Re: Multisource Ground Fault for MTTTTTTM Switchgear

05/16/2017 1:32 PM

GA, sorry the button only goes to "good", not excellent.

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