Fault in a home transferred to the grid

[Andpie]

Can an electrical fault in a residence be transferred out onto the service grid affecting other homes in the area on the same secondary side of the transformer?

 

[LarryFine]

Welcome to the forum.

Presuming the premises OCPD failed to open, yes, it could theoretically cause a primary fuse to open.

 

[electrofelon]

Can an electrical fault in a residence be transferred out onto the service grid affecting other homes in the area on the same secondary side of the transformer?

If you mean one transformer serving multiple houses, yes as Larry said it could blow the fused cutout serving the transformer. If it is a CSP transformer, it has a secondary circuit breaker and that would likely trip leaving your fellow neighbors in the dark. It is highly unlikely anything ahead of that single transformer would be affected.

 

[jaggedben]

Welcome to the forum.

Presuming the premises OCPD failed to open, yes, it could theoretically cause a primary fuse to open.

Or if a fault occured in customer owned service conductors on the line side of the service OCPD. Probably the most likely scenario for it, actually.

 

[ptonsparky]

Not just faults. It could be an added large intermittent load, such as on demand electric water heater, causing noticeable VD to the other homes.

 

[winnie]

Low current faults to earth could cause elevated neutral to earth voltages for everyone connected to the same transformer.

For example a fault to a non bonded well case could inject current into the soil without tripping a breaker or fuse. But everyone on the same transformer would experience the soil voltage gradient caused by this fault.

Jon

 

[ptonsparky]

Low current faults to earth could cause elevated neutral to earth voltages for everyone connected to the same transformer.

For example a fault to a non bonded well case could inject current into the soil without tripping a breaker or fuse. But everyone on the same transformer would experience the soil voltage gradient caused by this fault.

Jon

That scenario could affect those on other transformers as well.

 

[Andpie]

Ok well thank you everyone for that information. This is a great platform. When I said a “fault “ that was a very broad term. So that could cover just about everything.
So we know that the 220v / 240 v whatever the case may be is derived from the pole mounted transformer and we are not talking about a fault there. So correct me if I’m wrong but the voltage from the residence can never be more than it was supplied. That means we are talking about a fault current . In order to trip the network protection device on the primary side of the transformer the current would have to be extremely high. Agreed?
The service into the house looks unscathed. Main CB not tripped. Fire on the opposite side of the house from the service drop. So that means the fault was within a branch circuit. I’ll give you the benefit of doubt and say the fault occurred at an electric range on a 220v 50A CB. Question is - is that fault current enough to cause an issue at the neighbors house in anyway?

 

[ptonsparky]

Ok well thank you everyone for that information. This is a great platform. When I said a “fault “ that was a very broad term. So that could cover just about everything.
So we know that the 220v / 240 v whatever the case may be is derived from the pole mounted transformer and we are not talking about a fault there. So correct me if I’m wrong but the voltage from the residence can never be more than it was supplied. That means we are talking about a fault current . In order to trip the network protection device on the primary side of the transformer the current would have to be extremely high. Agreed?
The service into the house looks unscathed. Main CB not tripped. Fire on the opposite side of the house from the service drop. So that means the fault was within a branch circuit. I’ll give you the benefit of doubt and say the fault occurred at an electric range on a 220v 50A CB. Question is - is that fault current enough to cause an issue at the neighbors house in anyway?

VD issues, but actual damage would be stretching it, IMO.

 

[jaggedben]

.. Question is - is that fault current enough to cause an issue at the neighbors house in anyway?

Short answer: no. Not with the info you've given us.

As previous post says, voltage drop wouldn't conceivably cause damage anymore than having an outage and getting power back. If whatever neighbor's item is having the issue can't withstand that, then that thing was ready to fail on its own. Or it's just pure coincidence, assuming the neighbor isn't mistaken or dishonest about when their issue cropped up.

 

[don_resqcapt19]

Welcome to the forum.

Presuming the premises OCPD failed to open, yes, it could theoretically cause a primary fuse to open.

While that can happen, it is more often that the service conductors between the utility and the building act as fuses.

 

[electrofelon]

While that can happen, it is more often that the service conductors between the utility and the building act as fuses.

I find that hard to believe that their fuses are set that high. I tripped out a CSP transformer once.

 

[hbiss]

The service into the house looks unscathed. Main CB not tripped. Fire on the opposite side of the house from the service drop. So that means the fault was within a branch circuit. I’ll give you the benefit of doubt and say the fault occurred at an electric range on a 220v 50A CB. Question is - is that fault current enough to cause an issue at the neighbors house in anyway?

Ok, I get it now. Neighbor is alleging that an electrical fire in the house next door caused damage to something(s) in their house and is looking for compensation.

Just tell them "nice try".

-Hal

 

[LarryFine]

Just tell them "nice try".

And maybe suggest going after the POCO. They're the ones who brought the problem in.

(Presuming they can even show that that's what happened.)

 

[don_resqcapt19]

I find that hard to believe that their fuses are set that high. I tripped out a CSP transformer once.

Yes, sometimes the primary fuse blows, but typically they are sized not to protect the transformer, but to keep the next upstream fuse from opening. They want to keep the meters spinning as long as possible

 

[electrofelon]

Yes, sometimes the primary fuse blows, but typically they are sized not to protect the transformer, but to keep the next upstream fuse from opening. They want to keep the meters spinning as long as possible

Cooper recommends about 4 times nameplate FLC for primary fusing. I don't know if that holds for what utilities typically use in practice or not.

 

[shortcircuit2]

Could the OP's problem be an open utility neutral?

 

[jim dungar]

Yes, sometimes the primary fuse blows, but typically they are sized not to protect the transformer, but to keep the next upstream fuse from opening. They want to keep the meters spinning as long as possible

I have seen utilities only carry two sizes of fuses on their trucks. These fuses are for their conductors of which they also carry a limited number of sizes.

 

[Andpie]

Tortuga you got it only it's the POW CO that is claiming a fire broke out in one home (Neighborhood is hi end by the way 400A services) and the "Fire Effects" (what ever that means) were realized in the house across the street. I like "nice try" because I just don't see the fault current being placed back on the grid. Every OCPD would have had to fail the - branch circuit breaker and the main 200A breaker. All Cutler Hammer relatively new and not affected by the fire. Good low impedance ground fault current path was in place. Two grounding electrodes further than 6 feet were in place with good EGC's well connected. Good water pipe ground within inches of the copper pipe entering the building. All wiring was correct including grounded neutral at the first means of disconnect. Just sitting there with no damage. Just found out that breakers may have been manipulated by the FD at the time of the fire so no way to know if they tripped at the time of the incident. Also, yes the further away other houses are the less affected . Problem is that other homes in the area on the same secondary side of the transformer area a closed for the winter. Damages are unknown.
Found the service drop to the fire origin house severed by the POW CO post fire. I really don't believe in coincidences. Question remains can the fault in one home be transmitted out onto the grid and affect other homes fed by the same pole mounted transformer in this situation?

 

[Andpie]

And, yes was this a utility side fault that affected both (or all) homes on that tranny? Like loss of neutral as shortircuit2 suggests.