GROUNDING AND BONDING

Your use of language has me a little confused. Best advice... call a pro and have him check out the whole system. Without knowing exactly what it is you have on site, any advice other then that could be dangerous to the occupants of the "home" or "house" or "houses".

Having offered that... the return path for the fault current back to its source would have depended upon where the fault took place, as in "line to neutral" or "line to bond". If the fault was line to neutral, the neutral carried the fault current back to its source. If it was a line to bond fault, the bond conductor carried the fault current back to the source.

Have this checked out properly will you please.

Dear Guest,

A fault to ground is not the only event that will trip the breaker.

The two main protections built into most circuit breakers are short circuit, either line to ground or line to line, and overload.

Most circuit breakers are also designed to 'trip' and open a circuit when the current through the breaker is just over the breaker amp rating. This is the number printed on the breaker, usually on the trip reset handle. This is overload, and involves only a few amps over the rated constant load, and usually takes a while to cause the trip event.

Short-circuits involve upwards of 10,000 amps, and the trip event happens very quickly. Even then, in a few tenths of a second, the entire circuit feeding the faulted breaker will have handled the 10,000 or more amps. This seems to be what happened in the case you have described, since several other breakers in the circuit, with higher constant amp ratings, also opened.

You seem to be of the impression that a ground must be involved for this to happen.

Remember that a short-circuit allowing thousands of amps to flow can be from line to line also. The dirty rain water will provide a path across the hot lines in the panel box that can either carry a few amps, or thousands of amps. This is what happened in your case from your description.

Regards, CJM

Thanks for the help, I would like to know if the neutral should be grounded at the incoming MDB/meter panel (transformer is 3 phase 400 kva/220/380 vac) the wire from the transformer secondary goes from the transformer through PE pipe to the MDB Distribution board main breaker. There is no ground in this panel which is connected to a main breaker and goes to sub breakers feeding other panels through 3 phase meters. There are also ground rods driven and connected at each sub-panel.

4 different "electrical contractors" worked on installing the project. Drawings are not "as built", we are now meggering all wiring, repairing all connections and splices and trying to make a as Installed drawing.

Any help apperciated

Your use of terms still confuses me.

Who owns the transformer?

The voltages you mention make no sense. If it is a three phase transformer, the voltage should be 120Y/208 on the secondary and the primary should be what the utility provides. If it is a single phase transformer, the secondary voltage should be 120/240.

I will say it again, go get a pro.

The incoming 4 wires from the transformer, three phase conductors and a neutral, should go to a "main breaker" in "service entrance rated" main distribution panel. The neutral should be bonded to the case of the MDP and connected to a "grounding conductor" that is connected to a "ground electrode".

Feeds to the other buildings are what, single phase or three phase?

i am in a "foreign land" our transformers are 220/380. The "Pro's installed this mess"

I am an EE but graduated in 1967. I try and keep up, but here I have to "work around" what is installed and try and make the installation as safe as possible.

Here almost every house in 3 phase, with no 3 phase loads, all loads are single phase.

The transformer was purchase by the customer and installed by the electric company and than given to the electric company so they are responsible for maintenance.

"electricians" "Pro's" here only have a amp meter/voltmeter and a test screwdriver.

I have all the tools necessary to test the wiring, meggers, tik tracers, buried cable locators, TDR, and a staff that knows what they are doing, they are locals but follow western wiring methods as much as possible.

I did not post with a name or address because in previous posts local arm chair "engineers" criticize what we are asking, I only post when i need "advice" from other professional in my field.

On this and many other projects we have had problems with the contractors making splices in the PVC/PE ducting and buryng the splice.

We are left to fix/make this installation safe and we will if we have to redo all the wiring.

Hopefully you will understand the constraints we work under, we do not have the luxery of inspection or "Best Engineering Practices" we have to work with "what we got" ane make it as safe as possible, we use a lot of GLD "Earth Leakage Detectors"

these do provide a lot of protection, the nuseance tripping help us isolate problem circuits that we can than repair.

Sorry about terminology, different here. Have to deal with several languages and less that optimal education levels.

Thanks

I am not an electrical expert, but it sounds like you need to research and perform (or have some one qualified to perform) a "breaker coordination" study. Ideally, only the breaker closest to the fault should trip. In your case, the fault tripped several breakers almost simultaneously. The downstream breakers were set too high and were too slow to trip, or the upstream breakers were set too sensitive and were too quick to trip.

Blog or research breaker coordination, and set up your breakers so they do not all trip at once.

Dear guest, Having read your second post I think some information about how it is handled in most US areas could be of value.

I recognize the voltages given as common Wye voltages in several countries.

The Grounding (earthing) of the neutral is usually done in only 2 places. The secondary of the service transformer and the main service panel. Beyond the main service panel, the neutral is isolated from earth. This is done to prevent circulating currents through earth and to present a clear fault condition to the protective devices.

In your case, you have several separate houses, and in the US a service distribution transformer will have a grounded neutral, and each main service panel for each separate house will have a driven rod earthed neutral, which is then isolated from earth beyond the main. Neutral is isolated also through the sub panels that may exist in each house beyond the main service disconnect.

The term "there is no ground" hopefully refers to the non-earthing of the neutral rather than that there is no earthed electrode available or no earthing of the metal enclosures.

Our codes require that an earthed system be established that runs with the circuit conductors to enable many bonds to the earthed wire for equipment enclosures, metal plumbing, appliances - anything metal that might be energized accidentally. Metal pipes are not depended upon to provide the earthing, but instead are bonded to the earthing system wire or buss as a safety feature for the pipes.

There are a few exceptions, such as for electric stoves and for dryers, where the connecting flexible cord neutral can be bonded to the equipment case.

In some countries, the system is IT, meaning the neutral conductor and the earthing are accomplished with the same cable. This saves material, but then the equipment bonding becomes more critical and must be kept in good shape. I am less familiar with the exact details of those systems, but the 'I' indicates the neutral of the supply transformer is Isolated from earth and the 'T' means that the individual services are connected to Terra (earth) generally in a lot of places.

It would help if all electrical authorities had one set of practices, but the fact is that there are many differences around the globe. Usually based on cost of implementing the standards.

The good news is that the circuit breakers apparently did what they were designed to do - open the circuit to protect life and avoid fire. While it may have inconvenienced a few other houses, at least there was protection from the alternatives. Had the breakers not tripped, taking a bath in any of the houses could have been in lightning. Or enlightening as the case may be. (a play on English word usage)

Regards, CJM

PS: In regard to the 'breaker settings' mentioned previously; that applies usually for breakers above the residential realm. You will probably not find any settings to adjust or set on the system you are describing.

Hi,

There are no grounds anywhere at the main panel at the transformer, the panel has a main breaker and sub breakers as well as 3 phase meter which than go to other locations.

All breakers are adjustable in the distribution panels, the sub panels are Square D panels and breakers. I will look up the breaker model on the internet as see what the adjustments do, some have 2 and 3 adjustments on them, but they are all set the same???

There is no ground, no earthing conductor or ground rod is installed at the transformer MDB. I will install one, and bond it to the neutral. The conductors than go underground in a 2.5" PE pipe over 800 feet to the Main MDB, there is no ground conductor in this PE pipe, just the 3 phase wires and the neutral conductor.

I will megger the ground rod at the MDB at the end of the 800 foot run and make sure the ground to neutral is a good connection.

should we remove the ground rod connections at the individual small sub panels?

There is a lot of 12v landscape lighting and pond lighting on this property, all transformers are open frame type, how do ensure that if a transformer shorts 220 doesn't go to the fixtures, right now we will install 30ma earth leakage breakers on these circuits.

Sorry to throw something else into this mix.

The breakers are Merlin Gerin NS630N series.

Thanks

As CJMcGill has pointed out, there are different standards in use around the globe. you will need to verify what standard is in use where you live.

A good source of info can be found on grounding systems on the Wikipedia site. Here is a link... Wikipedia Link

If you read the material listed on that site, it reads that both Canada and the US use a TN-C-S grounding system. However the truth is a little different. The "N" in the "TN" is supposed to indicate that the consumer service relies upon the utility for its connection to "ground".

The truth is that we are really a "TT-C-S" system in the sense that for a consumer service, the neutral of the supply transformer is tied to ground, at the transformer (normally taken care of by the utility), then again at the service entrance of the consumer service.

The "C-S" portion is correct, we do not bring a separate PE in from the transformer. We create the PE at the consumer service. From that point on we keep the neutral and the PE separate.

The rest of this post will be based on the premise that you are in Canada. It would be appropriate for you as well, though, you will need to verify any "legal" issues yourself.

Essentially, the transformer is on the utility side of this equation, The secondary of the transformer should be tied to a "ground conductor" that runs to a "ground electrode".

I am going to assume that the transformer is on a pole of some kind, and as such, the ground electrode should be driven into the ground at the base of the pole and the ground conductor should run up the pole to the secondary neutral.

If the utility is following what is becoming the norm in distribution systems, the system may be connected Y on both the primary and secondary sides of the transformer. If so, the secondary neutral may be tied to the primary neutral and both will be connected to the ground electrode at the pole via the ground conductor.

Once the 4 conductors enter the main distribution panel. The three phase conductors go to your main circuit breaker and the neutral goes to the neutral bar in the MDP.

The neutral bar needs to be connected by a "ground conductor" of sufficient ampacity to a "ground electrode" and bonded to the case of the MDP.

As you mentioned, the runs to the other buildings are 4 wires only. As such, the incoming neutrals from the MDP must connect to the neutral bars inside each of the suite panels. Each suite panel neutral bar must be connected to a ground electrode via a ground conductor. The neutral bar must also be bonded to the case of each panel.

I am giving the description from what I understand from your posting and also give you reasoning.

You are having a transformer.The transfomer outgoing connected to main panel with MCCB/MCB say IC1.

This Main panel has got 8 outgoing MCCBs/MCBs say OG1-OG8.

From each of the outgoings cable is run and it is connected to sub Panlels 1-8 with MCCB/MCB say SUBPNL1_IC... SUBPNL2_IC ........ SUBPNL8_IC

The rain water has entered in one of the subpanels.

Due to rainwater entry there was a short between phases or Phase and earth.

Due to the above short circuit there was a fault current and it was very high.

Since there was very high short circuit current all the breakers(MCCBs/MCBs) has tripped.

May be there is no descrimination and coordination between the SUBPNL1_IC,outgoing OG1 and MainPanel IC.

In such fault conditions the breaker nearer to the fault must trip first,then up stream breaker and so on.

I think your problem is coordination of protective devices and not the grounding.

If you could share the information like make of device,setting of device, I can suggest suitable settings for the devices.

Ramvinod, I will state how I viewed this logic, and please clarify where it breaks down.

If the protection is correctly cascaded, the breakers will trip starting with the nearest one to the load circuit which experiences the problem. If not properly set, the Main breaker may open leaving some breakers closed that are closer to the problem. This causes outages on circuits with no problem.

In this case, all breakers including the main opened, indicating that breaker settings were ok even if not intentionally. It also appears to have been line to line since the sub, main and transformer breakers all opened, with no earth connection at the main or transformer.

If "In such fault conditions the breaker nearer to the fault must trip first,then up stream breaker and so on", and the breaker nearest the fault does open, how do the upstream breakers continue to open?

My thinking was that since all the breakers opened, the fault current was greater than any of the breaker settings, regardless of cascading settings.

I may have missed something I suppose, but these sound like much more than 'rooms', more on the level of a distribution transformer, main panel and pedestals in a mobile home park or retreat cabins. Depending on distance between, they should probably be considered separate dwellings where each gets it's own earth electrode.

It is quite possible the fault current was very high and all the breakers tripped simultaneusly.

I just looked at the Merlin-Gerin site.

It looks like they have merged with an U.S. firm, Schneider Electric.

I have also looked at the equipment they sell which all seems to be commercial/industrial, and looking further at some of the wiring diagrams, as I suspected originally, you are looking at three phase wiring systems or at least three phase equipment in what should be, if indeed those "houses" are indeed domiciles, a single phase environment.

But your language is speaking of "houses."

Are they really residential domiciles or have you for some reason chosen that language not sure of what language to use here on this international web site?

It seems pretty clear nonetheless that the breakers are three phase and are indeed adjustable.

If those multiple buildings are indeed residences somebody has spent an awful lot of money on what should be a simple three wire (Now four wire) system, i.e., ground, neutral, leg one and leg two of a single phase system no matter what the final secondary voltages.

Without a diagram I would not want to get into that mess. For instance how did rain water get into a panel? Was it outdoors and not a proper weather proof panel?

Are you going to have to replace all eight panels or move them indoors?

Do the utility companies there, it seems from the merger with Schneider that Merlin is indeed Canadian and so is your work site, allow distribution from a single main service panel to eight separate buildings (Residences).

j.

Hi, and thank you all for your expertise and help.

Indeed the "houses" are Individual and separate "rooms" on a single site that is a house, each "house/room is completely separate and each house has it's own electrical panel, all panels are 3 phase SqD, but as usual here there are no 3 phase loads, all loads are single phase.There are 9 separate (buildings) rooms on this 2 acre site overlooking the sea.

The panel that shorted was on a outside wall of a pool room, the "electrical" person ran the cable through a wall that leaked, they also splices the cable (after thought by electrical person, opps, forgot this circuit) and put in plastic box and buried the splice and box. We are digging up the box today.it is not unusual that wires are spliced in the conduit or buried here, they use a lot of silicone.

The thing is that this panel draws the least power of all panels on the site.

There Is NO power distribution drawing, I have to make one , and guess the underground cable routing.

What do you guys think of using ELCB (earth leakage circuit breakers) to protect sensitive electronics equipment and the kitchen and bathrooms circuits?

There is no driven ground rod at the Transformer distribution panel, the only ground is on the 2 poles that support the transformer, (galvinized cables) down the pole and into the ground.

Thanks

About the cables down the pole and into the earth; They probably end in a coiled pattern nailed to the flat bottom of the pole, which is how it is done here. except we use copper conductors.

The more important issue is where do they attach to the equipment racks or neutrals up on the pole. Can you verify that visually? This could add to the overall understanding of the earth and neutral situation.

CJM

I have attached a photo of the transformer installation.

Guest, On the right hand side there appears to be a conductor or conduit from the pole to the secondary terminal area, supported on an upright angled support. This could be the neutral ground bond.

Also on the left, there is strain relief from the secondary cable bundle that attaches to the pole, and could be a concentric shield from each cable that could serve as the transformer and service grounding electrode.

If there is a concentric running with the cables, it will be possible to establish the grounding at the transformer panel to include this.

Please spell out PE in reference to the conduit, as this could stand for Protective Earth and I am not familiar with it's use in your post.

It also appears that there are metering transformers above the service transformer, and I would expect grounding to be connected to those. Perhaps an elevated viewing point and a pair of binoculars will reveal some needed details. CJM

"What do you guys think of using ELCB (earth leakage circuit breakers) to protect sensitive electronics equipment and the kitchen and bathrooms circuits?"

No insult intended, but frankly, if you have to ask the above question I am not sure you are competent to do that job.

Those ELCB's, here in the states GFCI's (Ground fault circuit interrupters) are standard for any outlets in a bathroom or kitchen. They are intended to protect persons in the vicinity of good grounds from electric shock.

The protection of sensitive electronic equipment is a different issue solved a different way.

Others here have told you to bring in an expert, i.e., a licensed electrician and I am adding my voice to theirs.

Now you come up with service entrance cable splices (That is the way I regard the cable going to each of those boxes on those "houses"?? "rooms"??) which should simply not exist.

One thing is for sure. Whoever did that job originally must have been getting paid cost plus and so he chose equipment that would run the cost up. Three phase panels cost three or four times what single phase panels cost and the breakers as well let alone those adjustable ones.

You didn't say if those panels were weatherproof or not. If not and they are all outdoors they need to be replaced or moved indoors.

If you bring in a good contractor my bet is he will abandon everything from the pole to the building entrance points including those three phase panels, and start over. He will also carefully check the wiring in each of those structures.

A lot cheaper than digging up those cables that may, or may not, be spliced, just to see what they look like.

But again, no offense intended, your manner of describing what you are looking at and your language about it, suggest you should not be doing that job.

j.

We are checking all wiring in each house, connection by connection.

Earth leakage protection is not required here and the lowest available is 30ma here and they are not available in receptacles; they are separate surface mount breakers.

The grounds are being checked and megered also every plug and wired device, I have been away from the real world for a while so my terminology may be lacking as I have to deal with local "electricians" and terminology, but I did not design or install the system, my job is to Make It Safe.

I have NO Drawings, at least none the match the installation (as built)

It is also common practice to install 3 phase panel in homes, resorts and hotels here.

I realize in the real world, where I was a Licensed E.E. things were done correctly and inspectors kept you on your toes, we don't have the luxury of proper wiring devices, parts, or tools, we never see anyone here, after the meter it is up to you!

We try to use Western Wiring Methods (when possible) when we do jobs, however we are kept busy fixing the work of others.

All the panels are indoors and protected, the shorted panel was piped into a conduit that went through a cement roof with no protection from the rain.

I am simply asking for some advice from others in the field and getting opinions and help.

Trust me we have plenty of "Experts" here!

Hey Jack, A bit of historical perspective might ease some of your concerns.

In the US, for many years one center-tapped transformer out of 2 or 3 transformers in a Delta supply provided all single phase load. The result was a difficult to balance system.

In recent years, the transition has been to serve residences, and a lot of small businesses too, with Wye service to better enable balancing of the "plug loads" across all 3 transformers.

It is a very normal practice in many countries to utilize a 4w Wye service and sub-panels to aid in more fully utilizing the available distribution, since very little of it is used in 3phase devices. The result is a more balanced distribution cable load and results in balanced capacitive charging currents. Much easier to design and manage.

I'm not seeing much to be concerned about with the described incident, since I would expect these results from an immersed panel shorting across three lines. The mid-primary splices are also appropriate, if done in an approved manner and enclosed in a pull-box. These are the changes that guest is making from the information he has relayed to us.

The true shame is that there is no 'as-built' record of the installation that would be the least thing expected of the professionals. I applaud this guest for his efforts, and his patience with us.

Regards, CJM

CJ,

His comment and yours have put my mind at ease.

I looked again at the picture of the transformer and blew it up some.

Best I can make out from the writing on it, which appears to be Arabic, is that he is somewhere in Asia or one of the Arabian countries, though earlier I thought, because of the Merlin breakers, that he was in Canada or British Colombia, Newfoundland or some such.

The picture is interesting because if you look that location is not necessarily so isolated, at least relevant to that piece of geography. Coming over the top of that hill behind the transformer appears to be a high tension primary line.

Also, going by behind on about the same level as the transformer, is a three conductor distribution line which the transformer feeds may be coming off.

The secondaries from the transformer, and what must be a neutral, then go into what looks like ABS plastic pipe heading underground.

I wonder if he minds telling us where he is. Some of the stuff we see here raises all sorts of social questions, in this case for instance why are there eight houses on one feed with apparently one meter? Are they company owned, worker occupied, houses attached to some industrial operation?

In this country such things as workers occupying company houses is mostly behind us but when you read about the industrialization of China you find workers living in company dorms if not, in most cases, sleeping under their work benches as was true here in our not very distant past.

Truth be to tell, in my wilder days, I have seen in back country areas of this country (US) all kinds of wild electrical systems.

Matter of fact some years ago I set up a trailer in the backwoods. The power company would not drop me a line, because of county regs, until I had a county approved septic system but aside from that what I did afterward was entirely up to me. Since then local governments have gotten a lot tighter about adopting and adhering to national electrical codes.

I just got concerned about us helping some guy get himself and others in trouble. I am now satisfied although I do think that anybody that knows about GFCI's, regardless of local code, ought to be installing them. I do note he has not said he won't.

It does appear that what shorted that panel out was rain coming down a conduit that did not have a weather-head.

j.