Protection Requirement Phase to Neutral Short Circuit

Competent electricians and quality wire would help.

A circuit breaker will prevent the insulation of the wires from igniting. Without knowing where this extreme fault in a power distribution will happen it is difficult to say how or even if one can mitigate this type of fault. There are surge arrestor devices that one can install. Depending on where this arc flash condition happens you may only just roast the arrestor along with an appliance.

Sounds to me like you need to go yell at the utility. If an incoming phase conductor breaks and hits the neutral, the fusing on the utility side should blow.

On your side of the demarc, install a good quality surge suppressor.

I need soem resonable answer

ASAD

I guess hiring a licensed electrician in your area and having them size and install a proper surge protector for your location and wiring codes is not reasonable.

Let me ask you a question then. Is it reasonable to expect a precise answer from a group of distant, unpaid strangers that know nothing about your location, wiring standards, power demands, compliance or anything about your conditions? Particularly when the quality of the on site work can kill you and your family.

Hire a licensed electrician to install a proper surge protector.

To add to redfred's comment, I get the impression that you are in the field of electricity as either a paid consultant or a project person, and not just a homeowner asking for casual advice.

You must consult with the local authority who controls electrical installations and distribution, not an anonymous panel of unknown persons. We could all be raving idiots for all you know.

Seek professional, local help.

All of the answers so far are reasonable.

If you are only worried about your appliances' longevity, you can get a protection through an insurance company. Buy a policy that covers all of your appliances in case they breakdown and you do not have to worry about something that is out of your expertise..

Reliable, solid neutral connections are the domain of the local utility company. If their installation is causing damage to appliances, then claim on their indemnity insurance policy. The company will soon get the message if sufficient users complain in this way.

This is an overvoltage problem, not an overcurrent one. When the 440V conductor contacts the 220 one, the damage to equipment is instantaneous, then the overcurrent devices operate in response to the fault current but of course it's too late.

The best you could do is put an instantaneous overvoltage relay in to open a contactor in the low voltage line, but I doubt that it would operate fast enough. Surge arresters with a 250 MCOV will clamp fast enough, but since 440 is much higher than 250 it will fail open by overheating long before it would blow the 440 line fuse.

Chase the utility to fix their lines...good luck.

You beat me too it, Good post.

Very well put!

He should consider a RCD for each phase too, to protect the people in the house!!!!

I guess it depends on how much money you have to spend....I would probably go with a surge suppressor and a UPS system....possibly back-up generator for a total package...

http://www.smarthome.com/4860/Leviton-51120-1-Panel-Mount-Whole-Home-Surge-Protector-and-Supressor/p.aspx

http://www.dbstalk.com/topic/142754-finally-installed-whole-house-ups/

How did you manage to get 44oV on a phase to neutral? 220V but not the 3 phase voltage of 440V. NO surge arrestor nor CB nor fuse will help if you get 440V on a phase to neutral. Is your home direct on line with no protection.

I defy anyone to come up with a viable alternative to the BS1363 plug and socket.

Proviso:
The plug to be fitted with the correct fuse.

Disclaimer:
The fuse is to protect the cable only. It is not an overload device.

I agree with you completely, but how do you define "overload" in this case? That was unclear to me....It should protect both cable and device I feel....

I would have said (provided the correct sized fuse is used just as you said, not always the 13 amp ones sold with the plug!), that it is an "overload" protection.....it is simply not a reliable way to save lives, but it can save property (as you mentioned), that is where the RCD or similar takes over I feel....

I have heard that nowadays you can buy RCDs that also work as over current detectors as well....is that true? Maybe quite useful in countries where the plugs are not fused as in the UK and its dominions.

(Does any other plug/socket system have fuses inside the plugs?)

Plus, although the fuse is naturally totally brilliant, they are often "slow" (depending upon the value of the overload of course!), so good fast over current detection and almost immediate shutdown from a quality RCD/over current breaker, might actually be a good thing.....

Dear All , So far no perfect answer I found from this forum.

My question was simple i.e. if one of th 3phase 440 Vac , 50 Hz of utility supply broken & feldown on neutral ( with neutral ungrounded ) , means there will be phase to phase 440 V will applied to home appliances instead of 230 V. This will cause burn out of the home appliances.

If we applied 3 phase voltage protection relay with inst trip , it will some how protect the system but not perfectly i.e doubtful. Any slterance solution there . Most of the people looking for surge aresters , either they are good solution what will be the selection criteria of Surge arrester then ??????

ASAD

If your system allows what you are talking about, I would move to a country where they understand electricity better!! Should be easy!!!

I don't think that YOU understand how mains 3 phases actually work in most countries....

Andy G. -

I too agree, had sensed early on that he lacks a good understanding of power generation and distribution!

And for that reason had advised him to just get an appliance insurance that will address his concerns about " appliances breakage"...

You gave me a good (and very valid!) laugh with that comment!!! Thanks.

He does not seem to understand that a short to neutral, is also "quasi" a short to the neutral ends of the other two phases also.....but I have never seen or heard of such a short making the neutral 440 volts! How? When has he experienced that?

Normally the neutral is bonded to ground as well at some point for safety reasons, so effectively, you would have a phase short to neutral (and also effectively ground too), which should draw enough current to drop a circuit breaker I would have expected on the affected phase.

I am not prepared to test this out by the way for him......

Since no one else has offered what you think of as a perfect answer (surge arrestors and altering the home's protection scheme possibly violating local electrical codes are not ideal), mine would be-after sorting out with your utility and insurance company for replacement appliances).......................to Do NOTHING!!!

Hers my valid reasoning, realistically how often has this actually happened, and what are the chances of it happening again!

How many people do you know that protect their homes with protection capable of handling a direct phase to neutral fault due to a fallen conductor after the street's distribution transformer. I cannot think of any, can any other user on CR4?

Chalk this up to a freak accident and move on. Lightning protection is one thing but trying to do the utility provider's job better is quite another, and is quite likely to make things worse, not better.

440 vac 3 phase is not common in the average home. If that is what you have, call the utility company for service (and a qualified electrician).

Hi all, your replies are very interesting but somehow could not help Azad. I think he did not explain his problem clear to your understanding. I hope he has to add the following.

• The utility distribution system is 440/230v,4 wire, with bare (without insulation) over head conductors.
• The neutral is grounded at the source but still ground resistance normally high.
• If any phase conductor broken and fallen on neutral then other two phases which are connected to the houses will recieve 440v for some seconds before the main fuse blown at the source. Most of the time main fuse never blown and burnt all the loads.
• Sure this small time is enough to blow any house electrical appliences which are on operation at that time.
• There is no fuse available for neutral in the house.
• The phase fuse in the house is not technically calculated for its size, so will not blow before the source fuse blown.
• The utility cannot be approched or been complained.
• There is no insurance available to cover.
• unfortunately he cannont run away from his country for this issue.

Let us provide some simple, easy and cost effective solution for this issue.
A 2 pole contactor with 230v or lesser volt AC coil could be used to cut off the main supply. The coil to be connected with one point to neutral and the second with solid ground (which normally available in the house)whenever any phase conductor drops over neutral, it gets 230v across neutral and ground and the contactor will operate to cut off the mains. Its operating time may be 100ms, but still it may protect the house electrical appliences as well wiring insuation.
just try and good luck

but still it may protect the house electrical appliences as well wiring insulation.

Sorry but in reality it won't as, well it just wont. In addition to the fact it is very likely illegal due to local electrical standards.

Freak accidents like ASAD MALIK's are what house and contents insurance is for, I still believe that this is the best answer from the information supplied by ASAD MALIK. Re-inventing the wheel (so to speak) is not the right answer in this case.

....forgetting completely of course the safety of people that an RCD or similar brings too and has been mentioned I believe several times already.....the OP forgets that too!!

In case you need some further information about RCDs, look here:-

Residual-current_device

Your list is also incomplete and in some cases incorrect to my mind. Your solution would add even more danger to an already precarious state....especially for people....

If the OP is correct and the neutral is ungrounded (his second post #16), then there are several possibilities at least:-

1) get the utility company to correct their error as what he has at this moment IS EXCEEDINGLY DANGEROUS AND UNSAFE! An ungrounded neutral offers little or no protection as if a short happened between say the grounded frame of a device, there would be no extra current flow to rupture fuses. Even an RCD might have problems to trip correctly under such circumstances....as they need a difference in current between phase and neutral.

Furthermore an ungrounded neutral in an unbalanced phase situation (very common by the way) could experience wild swings of voltage at the neutral. Not conducive to proper working for sensitive devices....or people!

2) he grounds his own neutral. But preferably before the power meter. I am sure you know why! Though it would be a sin of the highest order in most countries to do this!! It would also go against code in most civilized areas in the world.....Its certainly not something I would do lightly.....but needs must when the devil drives.....

3) possibly the best solution safety wise might be a heavy duty star delta isolation 1:1 transformer. It would isolate him from the utility side errors of phase to neutral, he would not even need the utility neutral at all and he could safely earth the middle of the star "new" neutral on his side of the transformer. That would provide the best safety of all.

Even a single phase 1:1 transformer may supply enough of his needs....and cost less, as in the USA for example, but with no center tapped neutral, just one side of the transformer defined/connected as neutral/ground...

But he should still install RCD and over current breakers on his side of the transformer (either sort!)....the other side is the utilities problem. He might get a utility phase dropping, but nobody would be killed by it....

I do not know just how much power he needs, but such a transformer would not be cheap new, but secondhand, might be a good idea......IF SAFETY IS PARAMOUNT TO HIM.....