Distribution System Grounding

[suemarkp]

I know the secondary side of most power systems is grounded at the service and typically at the utility transformer secondary. What I'm wondering is if there is always a grounded conductor on the primary (distribution KV side), and is that grounded conductor directly bonded to the secondary grounded conductor of the transformer?

The reason why I ask is that I'd like to know how many return paths there are to a given transformer secondary. Is it only the electrodes connected to the secondary, or is every transformer and every ground electrode in the entire neighborhood effectively bonded together through miles of wire?

 

[hurk27]

Re: Distribution System Grounding

From what I know is the utility is required to bond to earth 4 times a mile, there will be a grounded conductor run down the poles that is also bonded to the secondaries of the transformers, And where they do use a delta primary they install what is called a zig-zag transformer to derive a neutral point to allow there primary to open there OCPDs.
I listen to Charlie E. on this and this is about as much as I can remember.
Maybe he will chime in and give you a better picture, if he's around.

 

[pierre]

Re: Distribution System Grounding

In the area that we work in, there can be many homes supplied by a Utility transformer, therefore leading to a lot of conductors leading back to this transformer, effectively connecting the different homes together.

A very recent example of this was a home with 70 amps on the cold water pipe, resulting in the pipe glowing. The Utility company denied that another person's home had any problems creating this situation. Over a period of 6 months, they spent several days testing, and even changing all of their overhead wiring.
6 months later (this problem persisted for the entire time), they finally had the other homes supplied by this transformer checked, and last week found the problem of a disconnected neutral in one of the other homes supplied by that transformer.

 

[iwire]

Re: Distribution System Grounding

Originally posted by suemarkp:
What I'm wondering is if there is always a grounded conductor on the primary (distribution KV side), and is that grounded conductor directly bonded to the secondary grounded conductor of the transformer?

Yes and Yes.

Originally posted by suemarkp:
The reason why I ask is that I'd like to know how many return paths there are to a given transformer secondary.

I think that would be a number between 1 and 1,000,000.

Typically there will be many return paths.

Originally posted by suemarkp:
is every transformer and every ground electrode in the entire neighborhood effectively bonded together through miles of wire?

Yes.

 

[ccjersey]

Re: Distribution System Grounding

There is such a thing as SWER (single wire earth return) distribution where there is no transmission line neutral to save money.

I would suspect on the secondary of each transformer served by such a line, the neutrals would be connected just the same as anywhere else.

 

[don_resqcapt19]

Re: Distribution System Grounding

I don't agree that there is always a grounded conductor on the utility primary. Not all of their distribution systems are grounded systems. Some are ungrounded delta. I will agree that there is always a grounding conductor on the primary side. I will also agree that the primary grounded/grounding conductor is almost always bonded to the secondary grounded conductor. This is the cause of most of our stray voltage problems.
Don

 

[iwire]

Re: Distribution System Grounding

I think we may be mixing codes.

The grounding and grounded conductors on the utility side are one in the same thing even if parts of the HV distribution system do not use it as a phase conductor.

Grounded and Grounding conductors are a product of the NEC are they not?

 

[don_resqcapt19]

Re: Distribution System Grounding

Bob,
If the utility distribution system is an ungrounded system there is no grounded or neutral conductor. I'm only using NEC terms to state the function of the conductor.

The grounding and grounded conductors on the utility side are one in the same thing even if parts of the HV distribution system do not use it as a phase conductor.

No they are not. They are installed differently and are not sized the same. In one case they are a part of the circuit and in the other case they are only a static bonding conductor. In most cases, at least in this area, if the utility system has a neutral conductor it also has a static bonding/grounding conductor. They are bonded together. Typically the bonding conductor is at the very top of the pole and is also used for lightning protection.
Don

 

[beanland]

Re: Distribution System Grounding

There is not always a ground on the utility side. Some utilities run single-point grounded 3-wire high-voltage distribution. A single-phase transformer will be connected phase-phase with two fuses. Only the secondary neutral is grounded at the pole/pad.