Primary falls on Secondaries...

[slick 50]

My bet.... The medium voltage hit the service drop GC. In an instant, from there to every neutral in the house and through the load, back to the breakers. I would bet the damaged breakers had the bigger loads?

still makes you wonder because if the medium vac contacted the GC of the service drop, it would have to bypass through the main disconnect which is bonded to the GEC. If it was seeking it source, you would think voltage would take the path from the disconnect instead of traveling to MLP. My guess is the current came in from the well pump circuit and destroyed the inside MLP and not the main disconnect since no damage is visible in the main.

 

[macmikeman]

The only grounding electrode is the rods, the well has plastic pipe entering the house. The grounding electrode system is all terminated in the outside service disco (new service 2 years ago).

This to me sort of furthers what I was wondering. I bet the earth had not much to do with anything and the fault path was concentrated on the ungrounded and grounded circuit conductors. Possibly current entered via the grounded conductor of the system, and at the service disco got onto the equipment ground conductor of the subfeeder ser via the service bond, traveled from the equipment bonding busbar and bonded metal surfaces of the sub panel board, arked to the grounded circuit conductors in the panel and wherever else, and returned to the source via the grounded circuit conductor(s). The service overcurrent device and the larger service conductors may have withstood the higher voltage imposed on them without noticeable damage, while the smaller branch circuit conductors at the subpanel and various devices did not withstand. My bet. Question is why the service overcurrent device did not open, perhaps the time duration was not enough to do its magic.

 

[mivey]

still makes you wonder because if the medium vac contacted the GC of the service drop, it would have to bypass through the main disconnect which is bonded to the GEC. If it was seeking it source, you would think voltage would take the path from the disconnect instead of traveling to MLP.

It would not have to bypass it. It could have (and probably did) use both paths.

My guess is the current came in from the well pump circuit and destroyed the inside MLP and not the main disconnect since no damage is visible in the main.

How did it get to the well first? What was the path (primary->secondary->neighbor ground->earth->well->well circuit->panel->secondary->primary?)?

 

[mivey]

The only grounding electrode is the rods, the well has plastic pipe entering the house. The grounding electrode system is all terminated in the outside service disco (new service 2 years ago).

This to me sort of furthers what I was wondering. I bet the earth had not much to do with anything and the fault path was concentrated on the ungrounded and grounded circuit conductors. Possibly current entered via the grounded conductor of the system, and at the service disco got onto the equipment ground conductor of the subfeeder ser via the service bond, traveled from the equipment bonding busbar and bonded metal surfaces of the sub panel board, arked to the grounded circuit conductors in the panel and wherever else, and returned to the source via the grounded circuit conductor(s). The service overcurrent device and the larger service conductors may have withstood the higher voltage imposed on them without noticeable damage, while the smaller branch circuit conductors at the subpanel and various devices did not withstand. My bet. Question is why the service overcurrent device did not open, perhaps the time duration was not enough to do its magic.

Primary->secondary->ECG or GC->who's your daddy->GC or ECG->secondary->primary

The service OCD may not have taken much of the hit?

 

[slick 50]

It would not have to bypass it. It could have (and probably did) use both paths.

How did it get to the well first? What was the path (primary->secondary->neighbor ground->earth->well->well circuit->panel->secondary->primary?)?

Oh Yeah, the forum was so long I forget that the OP said that the primary fell onto secondary. Lets just say it entered the home through a conductive path, probably the COAX cable that is bonded to the main disconnect......:-?:-?:-?:-?

 

[Pierre C Belarge]

The only grounding electrode is the rods, the well has plastic pipe entering the house. The grounding electrode system is all terminated in the outside service disco (new service 2 years ago).

This to me sort of furthers what I was wondering. I bet the earth had not much to do with anything and the fault path was concentrated on the ungrounded and grounded circuit conductors. Possibly current entered via the grounded conductor of the system, and at the service disco got onto the equipment ground conductor of the subfeeder ser via the service bond, traveled from the equipment bonding busbar and bonded metal surfaces of the sub panel board, arked to the grounded circuit conductors in the panel and wherever else, and returned to the source via the grounded circuit conductor(s). The service overcurrent device and the larger service conductors may have withstood the higher voltage imposed on them without noticeable damage, while the smaller branch circuit conductors at the subpanel and various devices did not withstand. My bet. Question is why the service overcurrent device did not open, perhaps the time duration was not enough to do its magic.

With the fact that the substation is so far from the house, I am leaning towards your ideas. I will study all the pictures I have (more than what I posted :grin, and think some more about this.

 

[mivey]

With the fact that the substation is so far from the house, I am leaning towards your ideas. I will study all the pictures I have (more than what I posted :grin, and think some more about this.

While you are looking: Was the secondary triplex or open wire? If triplex, I'm guessing the neutral was the starting path and we can only guess as to the main path past the bonding point. If open wire, was it horizontal or vertical and what was on top?

 

[Pierre C Belarge]

It is now triplex, I do not know what is was before I got there.

There is a brand new transformer that is supplied from the primary. The only house now supplied from this transformer is this house. Also a new pole supporting the transformer. This setup is approximately 75-100 feet from the house.

 

[mivey]

What about (for line-neutral fault):
primary source->secondary triplex neutral->some to panel neutral, some to customer ground, some to POCO ground/neutral then:

panel neutral-> some circuits & panel ground

then some circuits->panel ground

panel ground->customer ground->earth->POCO ground

customer ground->earth->POCO ground

POCO ground->POCO ground/neutral->source



OR for primary to secondary phase fault:

primary source->secondary triplex ungrounded conductor->panel main bus-> breakers-> some to panel ground, some to panel neutral, maybe some to feeders and arcing to ground/neutral then back to panel:

panel neutral & ground->customer ground & service neutral

service neutral->POCO ground/neutral->source

customer ground->earth->POCO ground->POCO ground/neutral->source

 

[mxslick]

With the fact that the substation is so far from the house, I am leaning towards your ideas. I will study all the pictures I have (more than what I posted :grin, and think some more about this.

Don't tease us, share some of the other pics.

 

[lefty]

I'm wondering what would all you fellows recommend to do to help prevent this from happening in the future, fused disconnects or whatever, I would like to hear your ideas.

 

[Pierre C Belarge]

Don't tease us, share some of the other pics.

They are not too much different than the ones posted, and would just take space and bore readers.

 

[mivey]

I'm wondering what would all you fellows recommend to do to help prevent this from happening in the future, fused disconnects or whatever, I would like to hear your ideas.

Surge protection or a generator.

 

[lefty]

can you give me some more specs that I should ask for on surge protection when I go to buy a device, or what would you recommend?

 

[hurk27]

Pierre
Not to long ago I posted about a very simular siduation HERE

and it was about the same set up except we had no BX/AC cable, just NM, so most of the pathways were through circuits and the electronics connected to the cable lines and phone lines.

But looking at you pic's does remind me of a time a POCO line man who was hooking up a OH upgrade service where the neutral was un-marked, without any testing he connected the transformer ungrounded conductor to the house neutral and it sparked, well he forced the two wires together and crimped it, then smoke started comming out of the home, what happened was in this house also there was no water pipe connection and all the BX had burned up to each point it crossed a water line and gas line, the cable line fell from the house on fire, and the fire department ordered the service line cut. so these could be some of the pathways your looking for, just think of any low impedance pathway back to the transformer then follow the flow.

The houses in the "here" link had many damaged NM cable runs that all the insulating jacket was blown off, but when we megged it out, it looked just fine, it was discovered when we rented a camera snake to view down the walls. so don't leave any stones unturned.

 

[hurk27]

I'm wondering what would all you fellows recommend to do to help prevent this from happening in the future, fused disconnects or whatever, I would like to hear your ideas.

There would not much that would have prevented the OP damage except maybe a city water supply system, properly bonded. surge suppressors would have had very little to no effect in stopping this kind of voltage or current. I have seen both what happened in the OP and as mention a higher voltage line hitting a lower voltage line, in both cases surge suppressors failed, and in the latter some caught fire,

 

[mivey]

can you give me some more specs that I should ask for on surge protection when I go to buy a device, or what would you recommend?

You can spend as much as you want but will never stop everything. Just think about lightning: It has jumped an air gap that is miles wide so what you do at the last few inches or even feet can't cure all the ills.

That said: At entry, you can start with an isolation transformer, a spark gap (a crowbar device that is basically an arrestor... meter might provide this), low-pass filters, and clamping devices like MOVs. This can be followed up with internal protection using point-of-use protection (surge strips and/or combo UPS devices).

You can buy hybrid transient voltage surge suppressors (TVSSs) that have a spark gap, low-pass filter and MOVs included.

You will not prevent the incident, only reduce the probability of greater damage.

Or you can put in a generator to isolate yourself from the utility.

As for me:
I'm not interested in spending loads of money at home. A computer/data center or manufacturing facility might be different. Time can mean a lot of money as well.

At home, I use surge protection strips on TVs, stereos, etc. I have SPDs and UPSs on my computer equipment. I have also made sure my service and panel are properly grounded.

As for the wiring, refrigerators, freezers, etc., the insurance is good enough for me.

I'm not sold on whole-house surge protection and don't mind installing them, but someone might be able to convince me otherwise.

 

[macmikeman]

Whatever happened, we all missed a terrific if not brief opportunity to test that "voltage stabilized with respect to ground" stuff:grin:

 

[mivey]

There would not much that would have prevented the OP damage except maybe a city water supply system, properly bonded. surge suppressors would have had very little to no effect in stopping this kind of voltage or current. I have seen both what happened in the OP and as mention a higher voltage line hitting a lower voltage line, in both cases surge suppressors failed, and in the latter some caught fire,

To address the high-energy transients, a spark gap is usually used. The whole-house devices I have seen don't look like they can handle that much energy. Not sure what the joule rating is but it is most likely intended to handle very brief surges causes by lightning, etc.

 

[Pierre C Belarge]

Whatever happened, we all missed a terrific if not brief opportunity to test that "voltage stabilized with respect to ground" stuff:grin:

If you like, I will fly you to NY. We are having a number of days with storms similar to the one that caused this damage. We are supposed to have a large number of storms on Friday.

Are you packed yet?