SINGLE WIRE EARTH RETURN (SWER) - not the same as "Multi Grounded Neutrals"

[mtnelect]

"It was first developed in New Zealand around 1925 for rural electrification. It was often called "Mandeno's Clothesline". In Australia over 100,000 miles have been installed, but it has several drawbacks, when used in very dry soil where the ground rods don't have good contact. This will elevate the risk of electric shock where the current could be as high as eight amps. Iti is recommended that the ground rods be longer and deeper to help reduce the high current".

Log in to "Wikipedia" for more details.

 

[jaggedben]

SWER and MGN are not the same thing.

 

[winnie]

IMHO single wire earth return and multi earth neutral are different beasties.

SWER always injects full primary current into the soil.

MEN injects a fraction of unbalanced current into the soil.

I would accept SWER as the limiting case of MEN with very high neutral impedance.

Jon

 

[mtnelect]

In my own opinion, they are both an abomination of the principles of electricity !

 

[mtnelect]

Just because you can do it, doesn't make it right. It's all about the money.

 

[mtnelect]

It's like the bidding system ... who can do it the cheapest.

That's why I got out of the racket.

 

[ActionDave]

I edited the original title to align with reality.

 

[winnie]

Just because you can do it, doesn't make it right. It's all about the money.

IMHO this unfairly singles out the cost factor, when there is also the 'effective grounding' factor in play.

Connecting transformers to that grounded neutral stabilizes the system to transients. (At least I've been lead to believe; I've not studied this in depth.)

I wonder if a compromise which maintains this benefit would be to connect all single phase loads L-L, and reserve the neutral for three phase loads which are inherently more balanced. This would minimize the load current (and voltage drop) on the neutral wire, which would minimize the current injected into the soil.

A perfectly balanced MEN system injects no current into the soil. A real utility system certainly does inject current into the soil.

Jon

 

[Birken Vogt]

Out in the middle of nowhere, Black Rock Desert there is a railroad communication building that is supplied by a single phase service.

There is no distribution voltage in the area but a 60 kv parallels the tracks.

They took one phase of the 60 and ran it to a side pole that has a large, strange looking rectangular transformer on it. Then a twisted triplex to the building.

The only connection down the pole is a single bare #6 copper guarded by a half round wood channel guard thing that pocos use which is of course falling apart.

I shudder to think what would happen if that copper got cut. I suppose it might also ground through the service neutral to the customer building but I don't know that.

 

[mtnelect]

I edited the original title to align with reality.

Thank you ... it makes more sense.

 

[mtnelect]

IMHO this unfairly singles out the cost factor, when there is also the 'effective grounding' factor in play.

Connecting transformers to that grounded neutral stabilizes the system to transients. (At least I've been lead to believe; I've not studied this in depth.)

I wonder if a compromise which maintains this benefit would be to connect all single phase loads L-L, and reserve the neutral for three phase loads which are inherently more balanced. This would minimize the load current (and voltage drop) on the neutral wire, which would minimize the current injected into the soil.

A perfectly balanced MEN system injects no current into the soil. A real utility system certainly does inject current into the soil.

Jon

I guess when you are living out in the middle of nowhere it makes sense. But, in the city it's the utility dumping on the customer. We must now bail out the utilities by installing copper mesh grid around our swimming pools because of the gradients caused by MGN. How about the utilities paying us for their abomination ?

 

[Birken Vogt]

I guess when you are living out in the middle of nowhere it makes sense. But, in the city it's the utility dumping on the customer. We must now bail out the utilities by installing copper mesh grid around our swimming pools because of the gradients caused by MGN. How about the utilities paying us for their abomination ?

In most of California, L-L is the default connection for a primary tx, with no neutral carried along. What is it like down south there?

I have traveled all over the west, and look out the window at powerlines everywhere, and by far the most common elsewhere is MGN L-N. All photos and videos and Streetview it's everywhere back east also. We are the outlier here.

 

[jaggedben]

Lots of potential faults or mistakes could cause a voltage gradient in a swimming pool without involving a utility MGN. I think that mesh would likely still be code required even if utilities did their grounding differently.

 

[mtnelect]

In most of California, L-L is the default connection for a primary tx, with no neutral carried along. What is it like down south there?

I have traveled all over the west, and look out the window at powerlines everywhere, and by far the most common elsewhere is MGN L-N. All photos and videos and Streetview it's everywhere back east also. We are the outlier here.

The problem is the connection of the primary to the secondary, then a connection to a ground rod adjacent to the pole and transformer above. Every utility pole has a ground wire hidden under a wooden molding that pumps the unbalanced current into the ground, which is called a gradient, depending on how close you are to the utility pole.

The utility saves the cost of a dedicated wire for the neutral, which would have to go all the way back to the substation. So, they just drive a ground rod at each pole and it "Leap Frogs" back to the substation ground rod to ground rod. All the while dumping gradient into the earth all the way back.

 

[mtnelect]

We peons must follow the NEC, but the utilities could care less. In a high wind weather incident, a transformer comes separated from the pole and falls on your car, so file a claim. It is then denied by the utility because it is caused by nature. They are exempted by government code.

 

[LarryFine]

The problem is the connection of the primary to the secondary, then a connection to a ground rod adjacent to the pole and transformer above. Every utility pole has a ground wire hidden under a wooden molding that pumps the unbalanced current into the ground, which is called a gradient, depending on how close you are to the utility pole.

The utility saves the cost of a dedicated wire for the neutral, which would have to go all the way back to the substation. So, they just drive a ground rod at each pole and it "Leap Frogs" back to the substation ground rod to ground rod. All the while dumping gradient into the earth all the way back.

Where have you actually encountered that, or are you just describing it?

 

[LarryFine]

In most of California, L-L is the default connection for a primary tx, with no neutral carried along. What is it like down south there?

I have traveled all over the west, and look out the window at powerlines everywhere, and by far the most common elsewhere is MGN L-N. All photos and videos and Streetview it's everywhere back east also. We are the outlier here.

Yes, here a neutral goes everywhere primaries do, bonding transformer cans, guy wires, switches, etc., and connected to electrodes at every pole with any equipment.

 

[curt swartz]

The utility saves the cost of a dedicated wire for the neutral, which would have to go all the way back to the substation. So, they just drive a ground rod at each pole and it "Leap Frogs" back to the substation ground rod to ground rod. All the while dumping gradient into the earth all the way back.

I think you are making this up. All of the Wye systems I have seen are 4 wire.

 

[Birken Vogt]

I don't understand Mtnelectrics assertion either, in my main territory (PGE 12 kv) there is no primary power neutral, 3 hots on distribution only. Primaries are not connected to secondaries at all. Nearby they have an (unusual for them) 21 kv distribution system like described on here where every tx is L-PN and the PN is jumped over to the customer neutral and ground as well, much like the rest of the country, but the PN is continuous all the way back to the sub, and they also make certain that the PN from any point has 2 ways to make it back to the sub, I guess so if it gets broken weird things don't happen.

 

[curt swartz]

I don't understand Mtnelectrics assertion either, in my main territory (PGE 12 kv) there is no primary power neutral, 3 hots on distribution only. Primaries are not connected to secondaries at all. Nearby they have an (unusual for them) 21 kv distribution system like described on here where every tx is L-PN and the PN is jumped over to the customer neutral and ground as well, much like the rest of the country, but the PN is continuous all the way back to the sub, and they also make certain that the PN from any point has 2 ways to make it back to the sub, I guess so if it gets broken weird things don't happen.

Actually pretty much all new circuits PG&E has built since the 80's have been 21/12kv wye circuits. They use the same 12kv dual bushing single phase transformers for both systems unlike other utilities that use single bushing. Their pad mounts have a switch that can be set for 21 or 12. This allows them to use the same equipment for both systems.