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Guru

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Auto Reclosing

02/09/2019 7:05 AM

Is it advisable to enable Auto Reclosing Function for Circuit Breakers feeding Underground Cable Networks? If yes, should it be single shot or multi-shot? What should be the typical dead time?

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Guru
India - Member - New Member Engineering Fields - Electromechanical Engineering - New Member

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#1

Re: Auto Reclosing

02/09/2019 7:40 AM

Why circuit is breaking and how frequent, Should be a question. And its answer can be helpful in deciding.

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Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

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#2

Re: Auto Reclosing

02/09/2019 9:13 AM

It can be advisable to use these devices. It can also be a bad choice. It all depends on a lot of other things not presented.

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Guru

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#3

Re: Auto Reclosing

02/09/2019 11:14 AM

If you have to ask, you probably should not.

I'd ask a local electrical expert, were I you.

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Guru
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#4

Re: Auto Reclosing

02/10/2019 9:03 AM

They were originally designed for OH lines as they are more susceptible to intermittent faults. Faults on UG cables are unlikely to be intermittent so reclosing on to the fault will just cause more damage.

So, no I don’t think it would be a good idea.

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Power-User

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#5
In reply to #4

Re: Auto Reclosing

02/10/2019 12:28 PM

You mean Transient fault (not intermittent fault).

In overhead line distribution, 80% of faults are transient nature and tripping and reclosing is the best way to restore the service fast. In case of Cable feeders, there are no transient fault. If insulation is damaged it cannot recover on its own, is damaged for good.

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Guru
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#6
In reply to #4

Re: Auto Reclosing

02/10/2019 1:32 PM

Agreed. In most cases if the fault occurs on a cable underground it is not intermittent so reclosing into a permanent fault is just a bad, bad idea.

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Guru
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#9
In reply to #4

Re: Auto Reclosing

02/11/2019 8:39 PM

45+ years back at engineering college one of our lecturers gave us a project as homework. It was to control a timed and monitoring sequence using opamps.

The circuit he had designed while working for a switchgear manufacturer in the early 60’s became our homework.

Fault.
Switch open.
Wait.
Switch close.
Switch open if fault is still there.
Wait.
Switch close.
Switch open if fault is still there.
Wait.
Switch close for a couple of seconds to try and burn the fault clear.
Switch open if fault is still there followed by Lockout.

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Guru
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#7

Re: Auto Reclosing

02/10/2019 1:33 PM

No.

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Guru

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#8

Re: Auto Reclosing

02/11/2019 12:06 PM

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