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Anonymous Poster #1

Short Circuit Protection

04/10/2017 7:43 AM

Hi All,

Can someone explain the following:

Current transformer on each phase for short circuit protection for 2 pumps complete with short circuit relays.

Above is related to a star delta control panel to control 2 pumps.

Please explain the use of short circuit relay and how they are connected, Examples of such relays will be much appreciated.

Thanks

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#1

Re: Short Circuit Protection

04/10/2017 10:08 AM

The relays open up when the current gets really big as measured by the current transformers. As for connections, you have two choices, series or parallel connections. Which would you choose?

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#2

Re: Short Circuit Protection

04/10/2017 1:25 PM

You want to have someone explain protective relaying in a forum post?

You know entire books have been written on the subject

Sizing CT,s is a critical procedures. CT,s have a bad habit of going into DC saturation during a fault. The C class must be choosen very carefully or the relay will essentially be blind. The scaling needs to be correct as well other wise your relay sensitivity will be incorrect and the relay will trip incorrectly. In order to calculate this correctly you must know the relay burden as well as the CT burden and the wire burden.

Im sorry but this is not something that can be explained in detail in a forum post with out a considerable amount of time. This is a complex topic. I would suggest one of many books on protective relaying.

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#3
In reply to #2

Re: Short Circuit Protection

04/10/2017 1:30 PM

What they really want is for someone to do their work for them, now that they have the job.

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#7
In reply to #3

Re: Short Circuit Protection

04/11/2017 9:25 AM

...and that costs...

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Anonymous Poster #2
#8
In reply to #3

Re: Short Circuit Protection

04/11/2017 10:12 AM

CR4: Conned Regularly. Lollipop site. For all the suckers.

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#9
In reply to #8

Re: Short Circuit Protection

04/11/2017 10:50 AM

Good one Annon II.

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#4

Re: Short Circuit Protection

04/10/2017 5:24 PM

Hi All,

Can someone explain the following: Why I stayed out all night and slept through class when they explained the fundamentals of short circuit protection?

I'm in over my head: Please explain the use of short-circuit relay and how they are connected, Examples of such relays will be much appreciated.

Straight up homework and this person is too embarrassed to identify themselves's

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Anonymous Poster #2
#5

Re: Short Circuit Protection

04/11/2017 2:50 AM

1.Current transformer: the sun dries out grapes which then become currents. The sun is a current transformer.

2. Short circuit relays: these are small races run around oval tracks by several people, to complete a set distance. Relay can be run in straight lines as well. Pony Express was a famous relay.

3. Electrical short circuit relays are connect with wires, Blue tooth does not work,

4. Check the wires on the back of electrical relays. if the wires are long they are not short circuit relays, they are long circuit relays.

5. Two examples of relays below.

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#6

Re: Short Circuit Protection

04/11/2017 6:19 AM

In jurisdictions where British Standard 7671 applies, short circuit protection (which is, after all, there to protect the wiring) is carried out usually with fuses and/or overcurrent breakers.

The individual best placed to explain how the circuit works is the individual that designed it, whose name is in the box on the "as built" drawing. Alas, the said drawing cannot be seen from here.

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Anonymous Poster #3
#10

Re: Short Circuit Protection

04/12/2017 12:34 AM

coolyar knows.

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