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10kv Bus Bar pt Feeder

12/27/2017 6:07 AM

In our power plant 10kv busbar pt feeder has interlock with incoming cb of busbar. i mean if pt is not in operation position you can not close the circuit breaker. is it necessary?

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#1

Re: 10kv Bus Bar pt Feeder

12/27/2017 4:17 PM

The best source of information is the documentation provided by the Designer and by the Commissioning Engineer. That documentation cannot be seen from here.

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#2

Re: 10kv Bus Bar pt Feeder

12/27/2017 5:20 PM

Are you employed at sahiwal coal power plant?

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#4
In reply to #2

Re: 10kv Bus Bar pt Feeder

12/27/2017 10:41 PM

yes

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#7
In reply to #4

Re: 10kv Bus Bar pt Feeder

12/27/2017 10:50 PM

Since you are employed there, you must ask those who made the decision. As has been stated, features that cost money are not included in designs unless they are needed.

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#3

Re: 10kv Bus Bar pt Feeder

12/27/2017 6:49 PM

My opinion is that every interlock is put in for a very good reason.

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#5

Re: 10kv Bus Bar pt Feeder

12/27/2017 10:42 PM

As stated by redfred every interlock is installed with a purpose and it adviced not to distrbed the orignal design, The designer may not be interested to have double on load switching.Or the CB of the Busbar pt may not be OCB/VCB . So better consult the original designer.

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#6
In reply to #5

Re: 10kv Bus Bar pt Feeder

12/27/2017 10:49 PM

sorry abraham i dont understand your point "double on load switching"

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#8
In reply to #6

Re: 10kv Bus Bar pt Feeder

12/27/2017 11:08 PM

this maybe ?

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#10
In reply to #6

Re: 10kv Bus Bar pt Feeder

12/28/2017 10:28 PM

" double on load switching" first your incomer switiching and then bus bar switching both on load . To avoid this interlock is provided.

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#9

Re: 10kv Bus Bar pt Feeder

12/28/2017 2:20 PM

If you close the breaker without a PT in position, to anyone looking at local or remote meters or to some of the protection, it will appear the busbar is dead.

Do you think that is a safe condition? Or is it worth an interlock to ensure safety?

If someone tried to insert a PT onto a live bus after closing the breaker, would that be safe for them?

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#12
In reply to #9

Re: 10kv Bus Bar pt Feeder

01/02/2018 10:26 PM

i admit the first point you mentioned that it will affect protection and metering at remote end.

but in my opinion it is unsafe to put a PT on energized busbar. What do you think?

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#14
In reply to #12

Re: 10kv Bus Bar pt Feeder

01/03/2018 10:50 AM

Munumibraheem,

No-one on CR4 can see the specifications and instruction manuals for your switchgear!

I mentioned the PT because this is one of the consequent actions, following the first error [energising the bus without a PT in place] which might cause an accident. Injuries and death usually have a succession of errors

Most HV switchgear has breakers which can be withdrawn for examination, maintenance, repair or replacement. This is achieved by having the breaker on a chassis or truck which can be drawn out and re-inserted. This comes with a mechanism and contacts which ensure the assembly stays earthed and the operator is at a safe distance and operations occur in the right order. There are both mechanical and electrical interlocks to ensure the breaker is open when it moves in or out. These facilities are the result of many years design effort, operational experience and testing.

Obviously, a PT could be made with live withdrawal/insertion safe - but the reliability of a PT suggests the space and cost are rarely justified.

Unless the manuals say a PT can be inserted and/or withdrawn live it would be dangerous and foolish to attempt. You risk a "10000 amp arc welder", or worse, loose. I suggest you consider what that could do in 0.1 second - find out how long the protection relays and breakers will take to cut off the current and what its magnitude will be.

Bus bar faults are very severe faults because there may be several in-going power sources plus current from load motors which act as generators.

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#16
In reply to #14

Re: 10kv Bus Bar pt Feeder

01/03/2018 11:43 PM

i think no arcing will occur because very little currents will flow in pt primary side

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#18
In reply to #16

Re: 10kv Bus Bar pt Feeder

01/12/2018 7:58 AM

True if the PT is not faulty when it is inserted!

In the event of damage or injury, you would have to justify why you bypassed a safety interlock.

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#11

Re: 10kv Bus Bar pt Feeder

12/29/2017 11:47 AM

Is your question "Is it ok to close a 10kV CB without having any source PT for your Instrumentation, Metering, and Safety/Protective Relaying?" Most readers here have already told you the answer...

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#13
In reply to #11

Re: 10kv Bus Bar pt Feeder

01/02/2018 10:28 PM

i want to know is it safe to put the PT in operation position in energized bus bar?

in my opinion it's "yes".

And i want to know any other reason of this interlock beside this safety measure.

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#15
In reply to #13

Re: 10kv Bus Bar pt Feeder

01/03/2018 9:00 PM

"... in my opinion it is unsafe to put a PT on energized busbar...", from your post #11,

"... is it safe to put the PT in operation position in energized bus bar? in my opinion it's "yes"... from your post #13.

What is your goal, to do away with the contact, justify its existence, second guess the original designer, explain away a bad decision, etc., etc.??

Hint: the correct answer depends upon the design of the PT, its mounting fixture, and/or the surrounding circuitry.

"What do you think?"

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#17
In reply to #15

Re: 10kv Bus Bar pt Feeder

01/03/2018 11:45 PM

i think there will be no arcing because very little current flow in pt primary side

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#19
In reply to #17

Re: 10kv Bus Bar pt Feeder

04/14/2018 12:15 AM

Do you know how dangerous is to rack in the PT while the VCB is fully energize, even everybody know that there is a very little current flow in pt primary side.?. At any mistake the whole PT cart can flash over and exploded right in front of you. That why it is interlock for safety reason.

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67model (3); lyn (2); munumibraheem (6); PWSlack (1); RAMConsult (2); redfred (1); Simon Wan (1); tonyhemet (1); V.I.Abraham (2)

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