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Line to Line Short

01/30/2017 7:45 AM

if a 11000 volt overhead line falls and becomes shorted with a 400V overhead line,but the fault do not involve ground ,what will be voltage at point of short between the two lines?

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#1

Re: line to line short

01/30/2017 8:25 AM

If the 11kV is not referenced to ground and the 400V is not referenced to ground then it is not possible to tell as the reference point for the voltage is not defined.

These birds, for example, do not experience a voltage:

as their reference point is not defined.

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#2
In reply to #1

Re: line to line short

01/30/2017 8:33 AM

both voltages are ofcourse referenced to earth. what i am saying is that the point of short does not involve ground fault.

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#3
In reply to #2

Re: line to line short

01/30/2017 8:35 AM

If both voltages are referenced to earth then the voltage after the event will be that which remains after either one or both circuit protective devices have operated. However, that situation is different from the premise in the original post: <...do not involve ground...>.

If the original post is a statement of intent to carry out a practical test, then please make sure all other CR4 readers are standing well away from the event prior to its taking place, preferably near a pile of dud 2V batteries.

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#7
In reply to #3

Re: line to line short

01/30/2017 10:16 AM

lol.i want you to witness the test

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#8
In reply to #7

Re: line to line short

01/30/2017 11:37 AM

Invitation declined. Video recording on YouTube is the way to go. How crass.

<unsubscribes>

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#37
In reply to #1

Re: line to line short

01/31/2017 5:04 PM

But they are at "Potential" relative to the other wires and earth. Not really an issue for the birds as they don't intend on making a circuit with either.

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#46
In reply to #37

Re: line to line short

02/03/2017 3:38 AM

Quite.

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#4

Re: Line to Line Short

01/30/2017 9:43 AM

This scenario is exactly one of the situations that equipment protection systems should disconnect. Therefore you do not provide enough information for a correct answer. More importantly you should not be grated permission to work on such equipment. You can cause millions of dollars of equipment damage and kill many people with such foolish acts.

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#5

Re: Line to Line Short

01/30/2017 10:00 AM

When you try this please take pictures!

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#6
In reply to #5

Re: Line to Line Short

01/30/2017 10:09 AM

Yes, even if we do not agree on religion or politics, we do agree that we like watching your fireworks.

Copper vapor makes such pretty fires from a great distance!

To answer your original question: There will be precisely 400 V on the line at the point of contact, since the 11KV line will arc to the 400V line before actual contact takes place, we can assume the 400V line is capable of carrying much higher current than the 11 KV line (maybe and maybe not), if so then the excess potential is merely shunted away momentarily before the 400 V line erupts into vapor and falls away from the point of contact.

The entire incident will not take very long to play out, since the circuit controls will trip both lines.

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#20
In reply to #6

Re: Line to Line Short

01/30/2017 2:37 PM

"Yes, even if we do not agree on religion or politics".

I don't recall ever having a disagreement about religion with you.

My disagreeing with you on matters of religion would be like Haris disagreeing with you about electricity. Much like a blind man trying to give you lesson in penmanship. Haris may bake a mean pizza, but he's electrically illiterate.

Politics? That's a horse of a different color. At least two members of your family are sane when it comes to politics.

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#21
In reply to #20

Re: Line to Line Short

01/30/2017 2:58 PM

Yes, me and my wife. LOL Two of my sisters are total dingbats. Talented dingbats, but still dingbats.

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#33
In reply to #5

Re: Line to Line Short

01/31/2017 9:05 AM

The occurrence of that particular problem may well be simultaneously the solution to another one.

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#34
In reply to #33

Re: Line to Line Short

01/31/2017 9:28 AM

Firefighters who turned up deliberately late to a burning pizza delivery company were reprimanded yesterday for making an ironic comment on their standard of service.

ProntoPizza of Balham, South London was burnt to the ground back in June despite being less than half a mile from Balham fire station.

When the flames initially broke out in the kitchen back on a busy Friday evening, the manager Peter Annal immediately called 999 and requested the fire brigade. But fifteen minutes later, with the inferno spreading to the shopfront and the upstairs rooms, the pizza chefs and delivery drivers were surprised to see a florist suddenly arrive with a bunch of flowers.

‘This big burly bloke came with a load of lilies and violets. He was clearly a fireman but he said he was delivering the wedding bouquet we had ordered. It was like he was suppressing the giggles the whole time.’

Mr Annal urgently explained that he had in fact ordered a couple of fire engines and the fireman apologised and said he’d have to go back to the station. Thirty-five minutes later, with much of the downstairs now completely gutted, the fireman returned with a complete Ocado shopping delivery.

‘It was then that one of our drivers recognised him’ explained Mr Annal. ‘He said that he often delivered pizzas to him at the fire station, and that the firemen had been repeatedly irritated by late and incorrect orders.’ A desperate Mr Annal then called the local police station who listened to what had happened. The police then sent round a window cleaner, a central heating engineer and some cold garlic bread.

‘A number of fire engines did finally turn up about three hours after we had initially called them’ said Mr Annal. ‘But by then the whole building had burnt to the ground. And one of them kept saying ‘Sooo sorry we didn’t listen to what you actually asked for. We really must listen more carefully next time…’

Yesterday at South London Magistrates Court, six members of the Balham fire crew were found guilty of gross negligence and ordered by the judge to pay the pizza company a £1 voucher for taking longer than thirty minutes.

source

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#35
In reply to #34

Re: Line to Line Short

01/31/2017 9:39 AM

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#36
In reply to #34

Re: Line to Line Short

01/31/2017 9:50 AM

Paybacks are hell!

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Anonymous Poster #1
#9

Re: Line to Line Short

01/30/2017 12:21 PM

Flitting from topic to topic like a butterfly, stopping at each one only to learn nothing.

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#10
In reply to #9

Re: Line to Line Short

01/30/2017 12:42 PM

Read a book.

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#14
In reply to #10

Re: Line to Line Short

01/30/2017 1:30 PM

Any good practical field related book you can recommend?

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#31
In reply to #14

Re: Line to Line Short

01/31/2017 3:59 AM

"The Book of Life's Learning Experiences", by coolyar. The number of pages therein is small by some current estimates.

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#23
In reply to #10

Re: Line to Line Short

01/30/2017 9:36 PM

AP#1 makes a good point: with each new day he's onto another, quite often unrelated, topic, never dwelling on any one of them long enough to master the concepts in depth. It's no wonder he keeps coming back with more questions, at the rate he's skipping around he's scarcely giving himself time to learn even the rudiments. He's got books and publications and documents - he's mentioned them by name - but back he comes, once again, with questions they've already answered for him, and in depth - if he'd only take the time to comprehend them.

Maybe instead of recommending a technical book, what of one with an aim to improving his study skills, reading comprehension, and critical thinking? I can't think of one offhand. Anyone?

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#24
In reply to #23

Re: Line to Line Short

01/30/2017 10:57 PM

Right. Tis Haris who should read a book, any book, and LEARN from the reading.

I fear there is no hope for our pizza boy.

Then again, I'm a cynic. Expect the worst and never be disappointed.

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#25
In reply to #24

Re: Line to Line Short

01/30/2017 11:07 PM

There's always hope, as long as he's breathing. If worse comes to worse he could always serve as a bad example. Always the optimist, I suspect he's probably just some bloke without a formal education trying to teach himself electrical principles and not having much success at it, given his apparent lack of study skills/reading comprehension. Maybe that's something that could be corrected, but he has to first believe he needs it and then go for it.

As far as his claims of being an E.E. employed by some outfit wot uses MW-generators and big electrical gear? I don't buy a word of it - he would have been found out by now. By somebody. By this time even the janitor would notice something amiss.

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#38
In reply to #23

Re: Line to Line Short

01/31/2017 10:59 PM

Andrew, when I enrolled in psychology 103, the professor handed us a syllabus. At the top of the first page was written in bold black letters,

HOW TO TAKE NOTES IN CLASS.

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#39
In reply to #38

Re: Line to Line Short

02/01/2017 11:04 AM

IT is truly hopeless, until IT gets a brain transplant.

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#40
In reply to #39

Re: Line to Line Short

02/01/2017 11:29 AM

I think Mr. Potato Head and Pizza Boy should start their own forum.

Maybe name it after a movie, like Dumb and Dumber!

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#41
In reply to #40

Re: Line to Line Short

02/01/2017 11:40 AM

Wow - seems like you are slipping a little bit in the harshness old buddy.

Almost like watching the Schumer and Pelosi Comedy Hour.

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#42
In reply to #41

Re: Line to Line Short

02/01/2017 11:42 AM

They're only smiling on the outside.

They, and I and about 100,000,000 others know that we are "On the Highway to Hell"!

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#43
In reply to #42

Re: Line to Line Short

02/01/2017 12:06 PM

Let's not go into who started that road, or the song. There is a turn off up ahead that reads "Highway to Heaven". Did you ever watch that show?

We are on the verge of something great here in America. The train is pulling from the station, and if you miss it, I am sorry for you. People all over the world - join the love train. Then we can have more freedom to move about.

When there are monsters out there wanting to kill Jesus' sheep, what shepherd would not act to protect the sheep? The bad actors must be stopped, and in the meantime, we sort out the sheep from the goats (bad actors), and protect the innocent while we start prosecuting war on the guilty. When entering into war (we are still in the longest war, and it shows no signs of being over any time soon), one must prosecute the other side with the most extreme prejudice available. This does mean prosecute the innocents here at home, nor the ones fleeing the evildoers.

A way will be found, but dropping the gates wide open is not the way.

Funny how discussing a line to line short devolved to this?

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#44
In reply to #43

Re: Line to Line Short

02/01/2017 3:26 PM

Sorry, old bean. You are right, but shame on you for the first digression, #6 and I never mention religion here because it has no place in a technical forum.

Not the case so much with politics, since they have a dramatic, and very soon devastating, effect on science and technology.

Besides this thread was DOA, anyway.

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#45
In reply to #44

Re: Line to Line Short

02/02/2017 10:29 AM

More like shorted out on arrival.

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#47
In reply to #40

Re: Line to Line Short

02/03/2017 3:40 AM

There is one already:

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#11

Re: Line to Line Short

01/30/2017 12:46 PM

Two pieces of metal in direct contact do not have a potential between them

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#12
In reply to #11

Re: Line to Line Short

01/30/2017 1:01 PM

but they do have "potential".

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#13
In reply to #12

Re: Line to Line Short

01/30/2017 1:30 PM

"potential"

Unfortunately, a quality you do not posses.

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#15
In reply to #11

Re: Line to Line Short

01/30/2017 1:33 PM

Not at the voltage levels described in this poser. However, a thermocouple is just two pieces of metal in direct contact making a potential voltage between. Be careful how you dismiss things.

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#17
In reply to #15

Re: Line to Line Short

01/30/2017 1:43 PM

Two different metals, I have every expectation that copper was used in these lines.

This was a trick question by the examiner, in a real situation the 11000 volt line would feed a high potential into the 400 volt line, unless the 400 volt line was insulated from ground to well above the 11,000 volts, and that whole 400 volt line and feeders would be raised to 11,000 volts. If an service or motor was turned to that would conduct to ground, then unless the 11,000 line was 100% floating = carnage.

Thus the examiners answer that two metals in contact do not support a potential difference.

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#19
In reply to #17

Re: Line to Line Short

01/30/2017 2:00 PM

Yes, I see that we at least agree that maple syrup with pancakes is a great idea, whilst dropping HVT on 400 V service is a really bad form idea.

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#16
In reply to #11

Re: Line to Line Short

01/30/2017 1:39 PM

The same kind of metal, that is a correct statement, however, dissimilar metals, I vote with thermocouple potential.

In this case, there will not be any wires there at all, since it will only be visible once the metal vapors have stopped conducting current, or the trips trip, but there will be a bright flash for a very short span of time.

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#18
In reply to #16

Re: Line to Line Short

01/30/2017 1:45 PM

I doubt they will ever actually touch while both voltages are present. As you earlier implied, the mechanical force from the arc flash will likely blow the loose cables away from each other.

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#22

Re: Line to Line Short

01/30/2017 8:56 PM

Model the circuit and find out. As a first approximation assume nothing untoward happens such as breakers tripping, wires melting, transformers blowing, fires, people dying; that sort of thing. Just as a circuit. How would you model it? What are the impedances (even if symbolic)? The relative phase? Mind you this is only a first approximation, but it is a circuit, even so, and so you should be able to model it as a circuit, no? Do it and find out, then add reality as necessary.

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#26

Re: Line to Line Short

01/31/2017 12:10 AM

Now, Is there a line to ground short?

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#27
In reply to #26

Re: Line to Line Short

01/31/2017 12:12 AM

He said there is not.

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Guru

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#28
In reply to #27

Re: Line to Line Short

01/31/2017 12:17 AM

Just asking.

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#29
In reply to #28

Re: Line to Line Short

01/31/2017 12:20 AM

Don't ask!

Just go away.

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#32
In reply to #29

Re: Line to Line Short

01/31/2017 7:50 AM

Really, Lyn?

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#30
In reply to #28

Re: Line to Line Short

01/31/2017 12:22 AM

Why are you cringing? I didn't mark you OT. I simply answered your question.

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