T
taylorp
Guest
Mr. Campbell:
Could you explain what you mean when you wish we could do away with a grounded system? Just curious.
- Status
Could you explain what you mean when you wish we could do away with a grounded system? Just curious.
charlie
Senior Member
- Location
- Indianapolis
Re: Outdated/Antiquated US Elect. System?
I think what Dereck meant was that the wye system that is the normal system in the US is using a very well grounded neutral (multi-grounded). Transformers are normally connected from the phase wires to the multi-grounded system neutral. As long as the loads are balanced, the return current stays with the main feeders. However, most of the main feeders from the substations are not well balanced and there are long single phase taps that also have some return current to the substation transformer.
Don Zipsie and Mike Holt both advocate revamping the distribution system to require the power companies to run a grounding conductor in from all transformers and banks. This would change the grounding at all services to connect the grounding electrode system to the grounding conductor and leave the neutral floating (no different than a distribution panelboard). Additionally, all transformers would be required to be connected from phase to phase to prevent any current return through the earth.
Sounds like a great system but the cost would be very prohibitive. Imagine the extra cost of replacing all of out transformers and replacing a lot of our poles to handle the extra transverse loading and pole height for the extra conductors for starters. The electric utilities will not pay for this conversion, the consumer will pay for it. This has been looked at before and the estimate is a surcharge that will double your electric bill for about 10 years and then about 10% more on the base to maintain the different system.
I do not personally believe this can ever be cost justified in the pocketbook of the consumer.
I think what Dereck meant was that the wye system that is the normal system in the US is using a very well grounded neutral (multi-grounded). Transformers are normally connected from the phase wires to the multi-grounded system neutral. As long as the loads are balanced, the return current stays with the main feeders. However, most of the main feeders from the substations are not well balanced and there are long single phase taps that also have some return current to the substation transformer.
Don Zipsie and Mike Holt both advocate revamping the distribution system to require the power companies to run a grounding conductor in from all transformers and banks. This would change the grounding at all services to connect the grounding electrode system to the grounding conductor and leave the neutral floating (no different than a distribution panelboard). Additionally, all transformers would be required to be connected from phase to phase to prevent any current return through the earth.
Sounds like a great system but the cost would be very prohibitive. Imagine the extra cost of replacing all of out transformers and replacing a lot of our poles to handle the extra transverse loading and pole height for the extra conductors for starters. The electric utilities will not pay for this conversion, the consumer will pay for it. This has been looked at before and the estimate is a surcharge that will double your electric bill for about 10 years and then about 10% more on the base to maintain the different system.
I do not personally believe this can ever be cost justified in the pocketbook of the consumer.
Re: Outdated/Antiquated US Elect. System?
A grounded wye (or center tapped sp.) on the LV side appears to be the most common system in the world while practices differ on the MV side.
The additional cost of running a grounding conductor isn't as bad as you may think, since the it can be made considerably smaller than the live conductors. The Brits used the cable armour as the grounding conductor but to save money, they eventually went for the American practice with a combined neutral/grounding conductor. Some places, e.g. France, rely on the ground rod in conjunction with a GFI instead of bonding the grounding conductor to the grounded conductor. This lessens the risks associated with a loose grounded conductor, but should the GFI fail the equipment grounding effectively becomes useless.
A grounded wye (or center tapped sp.) on the LV side appears to be the most common system in the world while practices differ on the MV side.
The additional cost of running a grounding conductor isn't as bad as you may think, since the it can be made considerably smaller than the live conductors. The Brits used the cable armour as the grounding conductor but to save money, they eventually went for the American practice with a combined neutral/grounding conductor. Some places, e.g. France, rely on the ground rod in conjunction with a GFI instead of bonding the grounding conductor to the grounded conductor. This lessens the risks associated with a loose grounded conductor, but should the GFI fail the equipment grounding effectively becomes useless.
charlie
Senior Member
- Location
- Indianapolis
Re: Outdated/Antiquated US Elect. System?
In order to run a grounding conductor, you have to have an additional 8 in. of pole space and more pole strength for transverse loading. Additionally, there will be guying involved if this is built overhead. Generally speaking, about 1/3 of the poles will have to be replaced to make this system work.
What I am thinking about is the overhead secondary in residential neighborhoods. New services would not be much of a problem except for the high cost of the 15 kV class (HV side) transformers. Additionally, a 3 phase service would now require the third primary phase since open deltas would no longer work. Also, all single phase transformers would require 2 primary phases.
All underground cable in subdivisions that is set up for single phase transformers are now going to have to have a second cable in order to get the second phase. There will be a utility crew in your back yard sometime in the future.
You are talking about a major rebuild of the US electrical system. Please reread my first answer.
In order to run a grounding conductor, you have to have an additional 8 in. of pole space and more pole strength for transverse loading. Additionally, there will be guying involved if this is built overhead. Generally speaking, about 1/3 of the poles will have to be replaced to make this system work.
What I am thinking about is the overhead secondary in residential neighborhoods. New services would not be much of a problem except for the high cost of the 15 kV class (HV side) transformers. Additionally, a 3 phase service would now require the third primary phase since open deltas would no longer work. Also, all single phase transformers would require 2 primary phases.
All underground cable in subdivisions that is set up for single phase transformers are now going to have to have a second cable in order to get the second phase. There will be a utility crew in your back yard sometime in the future.
You are talking about a major rebuild of the US electrical system. Please reread my first answer.
Re: Outdated/Antiquated US Elect. System?
Sorry to be late. Looks like Charlie championed my cause. Another method I like for residential would be a 240/120 system with no grounded conductor. Just like the 120/60 used for technical power systems.
Sorry to be late. Looks like Charlie championed my cause. Another method I like for residential would be a 240/120 system with no grounded conductor. Just like the 120/60 used for technical power systems.
charlie
Senior Member
- Location
- Indianapolis
Re: Outdated/Antiquated US Elect. System?
C-H, I am discussing secondary as well as primary. Take another look at my comments.
People can have silver lined gutters if they want to pay for the cost of installing them. This comes under the same heading. If we had started this system at the time we were building the electrical infrastructure, we would not have this problem. As it stands now, I think it is a system we will have to live with and learn how to mitigate the problems that we encounter (we are doing a pretty good job of doing just that).
C-H, I am discussing secondary as well as primary. Take another look at my comments.
Sorry Dereck, I guessed at your position and stated it; however, I don't agree with it.
People can have silver lined gutters if they want to pay for the cost of installing them. This comes under the same heading. If we had started this system at the time we were building the electrical infrastructure, we would not have this problem. As it stands now, I think it is a system we will have to live with and learn how to mitigate the problems that we encounter (we are doing a pretty good job of doing just that).
Re: Outdated/Antiquated US Elect. System?
Sorry Charlie, I was not attacking the utility industry. Remember I came from a utility once upon a time. I realize the expense that would have to be undertaken.
When it was developed every thing was prety much linear load, harmonics were of no concern, and who cared at the time about earth being used as a conductor.
I think a good economical first step would to be supply the EGC from the transformer. But I also realize that would put responsibility of user protection on the the utility.
If I had my way everything would be 3-phase. :roll: But here is some food for thought. What if all applinaces, loads, etc used in residence were 240 L-L operated, no neutral needed, only referenced to ground at the center tap to provide a safe and effective fault clearing path and voltage stability.
[ October 05, 2004, 02:02 PM: Message edited by: dereckbc ]
Sorry Charlie, I was not attacking the utility industry. Remember I came from a utility once upon a time. I realize the expense that would have to be undertaken.
When it was developed every thing was prety much linear load, harmonics were of no concern, and who cared at the time about earth being used as a conductor.
I think a good economical first step would to be supply the EGC from the transformer. But I also realize that would put responsibility of user protection on the the utility.
If I had my way everything would be 3-phase.
:roll: But here is some food for thought. What if all applinaces, loads, etc used in residence were 240 L-L operated, no neutral needed, only referenced to ground at the center tap to provide a safe and effective fault clearing path and voltage stability.[ October 05, 2004, 02:02 PM: Message edited by: dereckbc ]
charlie
Senior Member
- Location
- Indianapolis
Re: Outdated/Antiquated US Elect. System?
Had I thought that, I would have let it lay. I thought this was the start of a good thread so I responded to it. I am guessing that most electricians are not familiar with electric distribution.
I think I would have a problem with replacing all the lamps, radios, TV, microwaves, toasters, stereos, 120 volt motors, etc. in my home to buy into that idea. This goes back to the silver gutters that I was talking about.
Re: Outdated/Antiquated US Elect. System?
All kidding aside, I enjoy a good debate, it opens our minds to a different prospective, and innovative thinking.
Well heck, it' a good opener. Truth is any change to electrical distribution architecture would be bought?and paid for by us consumers. That's the AMERICAN way
All kidding aside, I enjoy a good debate, it opens our minds to a different prospective, and innovative thinking.- Status