Stray Neutral Current along Wye distribution lines
- Thread starter snflbruce
- Start date
- Status
Re: Stray Neutral Current along Wye distribution lines
Roger: I was about to post the same thing. Maybe Scott is eavesdropping and will jump in.
I recommend for reading;
Introduction to "Electrical Power System Technology" by Theodore R. Bosela, Youngstown State University.
Roger: I was about to post the same thing. Maybe Scott is eavesdropping and will jump in.
I recommend for reading;
Introduction to "Electrical Power System Technology" by Theodore R. Bosela, Youngstown State University.
scott thompson
Senior Member
- Location
- Anaheim, California
Re: Stray Neutral Current along Wye distribution lines
Roger and Bennie;
I just stumbled across this thread, and so far everything is pretty much covered!
Thanks for suggesting the ECN references per the Zig-Zag Setups. If the original topic poster (bruce) would like to ask some Qs regarding the Z-Z setups, feel free to ask away!
Do this either here, at ECN, or with a P.M. / E-mail. Suggest posting to this thread, or posting at ECN, as opposed to private messaging - simply to get many opinions and examples.
Scott
Roger and Bennie;
I just stumbled across this thread, and so far everything is pretty much covered!
Thanks for suggesting the ECN references per the Zig-Zag Setups. If the original topic poster (bruce) would like to ask some Qs regarding the Z-Z setups, feel free to ask away!
Do this either here, at ECN, or with a P.M. / E-mail. Suggest posting to this thread, or posting at ECN, as opposed to private messaging - simply to get many opinions and examples.
Scott
Re: Stray Neutral Current along Wye distribution lines
Bruce,
Given that the SWER system is used in areas which are sparsly populated, the health risks are likely to be very small. If you have some distance to houses, say 10 ft/amp, I don't see the problem. I'm sure Karl Riley has an opinion on this
But I'm as puzzled as you as to why a delta can't simply be used with a ground fault relay. I looked up the law where I live (Sweden). On overhead lines, other than LV, it requires ground fault detection which trips on ground faults with a resistance of 5000 ohms or less.
Bruce,
Given that the SWER system is used in areas which are sparsly populated, the health risks are likely to be very small. If you have some distance to houses, say 10 ft/amp, I don't see the problem. I'm sure Karl Riley has an opinion on this
But I'm as puzzled as you as to why a delta can't simply be used with a ground fault relay. I looked up the law where I live (Sweden). On overhead lines, other than LV, it requires ground fault detection which trips on ground faults with a resistance of 5000 ohms or less.
Re: Stray Neutral Current along Wye distribution lines
Bennie and Rodger,
Thanks so much for the reference to the EC site and Scott. It really is a great resource.
Alas the text Bennie mentioned is not in print and I couldn't find a used copy online. Any suggestions for a currently in print text?
Scott,
Thanks for joining in. I looked at the zig zag transformer schematics on your references page. You really have done some fabulous work on the EC site. I've registered there and will definately spend some time there.
It looks to me like a zig zag is not something which would apply to a two wire distribution line of 10KV feeding a residential transformer. Or am I mistaken? Nor did I see any primary voltage short to secondary protection inherent to the zig zag.
I guess I'll have to talk with my local power co. supervisor to find out what primary to secondary short protection they are using on the existing two wire, 10KV distribution line which he mentioned was somewhere in this area.
Can you suggest an in-print text on power transmission for me?
Thanks!
C-H,
I think the SWER system would create essentially totally a net current situation, with magnetic fields falling off only linearly with distance. If SWER was used only for transmission over uninhabited areas, then only the wildlife would be affected. It seems a false economy (to save a second wire).
In Wye systems that I've measured, some "current mirror" effect is present; unless presented with a better path (like an aquifer or any conductor), a good portion of the ground current wants to follow under the lines. Alas, the effect seems pretty weak, and grounded wells seem to offer too good a path to the aquifer. It's unclear to me how the SWER ground currents will behave.
I think we're in different frames of reference regarding acceptable magnetic field levels. Ten foot per amp of net current will result in some pretty high levels. The line I've been looking at is estimated by Karl R. to have 8 amps of net current (based soley on my readings). I find the present magnetic field levels "acceptable" (10 microgaus) at over 1/4 mile (1320 ft). I normally see much faster drop off than I do along this line, and I'm not sure just yet why. Once the neutral line current is checked, I may know more. Another factor which I haven't determined is whether magnetic fields from above ground net current are as problematic for me (and hysterical cows) as ground current caused fields.
By definition SWER will create ground current levels substantially higher than even the MGN (Wye) system. Ground currents (despite quite low magnetic fields- levels that don't seem bothersome if from sources not flowing through the earth) seems to adversely affect both livestock and some people very profoundly. I don't believe the problem is unique to dairy farms in the US. Let's test it first in Sweden.
Interesting that Sweden has ground fault relays on the transmission lines. What is considered low voltage in your law relating to GF relays? I wonder if ground fault relays are used on HV lines here in the US?
Bruce McCreary
Bennie and Rodger,
Thanks so much for the reference to the EC site and Scott. It really is a great resource.
Alas the text Bennie mentioned is not in print and I couldn't find a used copy online. Any suggestions for a currently in print text?
Scott,
Thanks for joining in. I looked at the zig zag transformer schematics on your references page. You really have done some fabulous work on the EC site. I've registered there and will definately spend some time there.
It looks to me like a zig zag is not something which would apply to a two wire distribution line of 10KV feeding a residential transformer. Or am I mistaken? Nor did I see any primary voltage short to secondary protection inherent to the zig zag.
I guess I'll have to talk with my local power co. supervisor to find out what primary to secondary short protection they are using on the existing two wire, 10KV distribution line which he mentioned was somewhere in this area.
Can you suggest an in-print text on power transmission for me?
Thanks!
C-H,
I think the SWER system would create essentially totally a net current situation, with magnetic fields falling off only linearly with distance. If SWER was used only for transmission over uninhabited areas, then only the wildlife would be affected. It seems a false economy (to save a second wire).
In Wye systems that I've measured, some "current mirror" effect is present; unless presented with a better path (like an aquifer or any conductor), a good portion of the ground current wants to follow under the lines. Alas, the effect seems pretty weak, and grounded wells seem to offer too good a path to the aquifer. It's unclear to me how the SWER ground currents will behave.
I think we're in different frames of reference regarding acceptable magnetic field levels. Ten foot per amp of net current will result in some pretty high levels. The line I've been looking at is estimated by Karl R. to have 8 amps of net current (based soley on my readings). I find the present magnetic field levels "acceptable" (10 microgaus) at over 1/4 mile (1320 ft). I normally see much faster drop off than I do along this line, and I'm not sure just yet why. Once the neutral line current is checked, I may know more. Another factor which I haven't determined is whether magnetic fields from above ground net current are as problematic for me (and hysterical cows) as ground current caused fields.
By definition SWER will create ground current levels substantially higher than even the MGN (Wye) system. Ground currents (despite quite low magnetic fields- levels that don't seem bothersome if from sources not flowing through the earth) seems to adversely affect both livestock and some people very profoundly. I don't believe the problem is unique to dairy farms in the US. Let's test it first in Sweden.
Interesting that Sweden has ground fault relays on the transmission lines. What is considered low voltage in your law relating to GF relays? I wonder if ground fault relays are used on HV lines here in the US?
Bruce McCreary
Re: Stray Neutral Current along Wye distribution lines
Bruce,
Low voltage would be less than 1kV.
We are talking about different magnitudes of the magnetic field. You mention 10 ?G as an acceptable level. I and another million people who live in this city are exposed to magnetic fields from net currents tens or even hundreds of times higher and we are still alive.
Have you checked the magnetic field from a hairdryer or a shaver?
Bruce,
Low voltage would be less than 1kV.
We are talking about different magnitudes of the magnetic field. You mention 10 ?G as an acceptable level. I and another million people who live in this city are exposed to magnetic fields from net currents tens or even hundreds of times higher and we are still alive.
Have you checked the magnetic field from a hairdryer or a shaver?
Re: Stray Neutral Current along Wye distribution lines
CH- I've done over 10 years of work in EMF mitigation, so yes, I do know the emission profiles of most common appliances.
One of the first and largest support groups for people with "ES" or electrical sensitivity (I hate that name) is actually in Sweden. Some of the founders were electrical (circuit design) engineers. They aren't dead either.
Best Wishes,
Bruce
CH- I've done over 10 years of work in EMF mitigation, so yes, I do know the emission profiles of most common appliances.
One of the first and largest support groups for people with "ES" or electrical sensitivity (I hate that name) is actually in Sweden. Some of the founders were electrical (circuit design) engineers. They aren't dead either.
Best Wishes,
Bruce
scott thompson
Senior Member
- Location
- Anaheim, California
Re: Stray Neutral Current along Wye distribution lines
Bruce;
Glad to be of assistance!
Also to derive a Grounded Conductor / Grounding Reference where none is existing (sorry for the lame terms!).
The OCPD on the circuit of which the Zig-Zag is derived from, may be sufficient, otherwise place correct OCPDs in series with the Zig-Zag (if required... may be along the lines of fusing a Grounded Conductor - so likely to be a "No-No" to fuse the inputs of the Zig-Zag!).
* ANSI C84.1 - 1995: American National Standard for Electric Power Systems and Equipment - Voltage Ratings (60 Hz),
* IEEE "Red Book" and "Green Book"
See you at ECN!
Scott
p.s. What's your handle at ECN?
Bruce;
Cool!
Also Cool!
Glad to be of assistance!
Zig-Zags are commonly used within an enviroment which utilizes a Poly Phase System - like 3? (or 2? for the really old areas!).
Also to derive a Grounded Conductor / Grounding Reference where none is existing (sorry for the lame terms!).
The OCPD on the circuit of which the Zig-Zag is derived from, may be sufficient, otherwise place correct OCPDs in series with the Zig-Zag (if required... may be along the lines of fusing a Grounded Conductor - so likely to be a "No-No" to fuse the inputs of the Zig-Zag!).
Probably just the Grounding of the Secondary for a Winding Flash-Over situation...
Try these out:
* ANSI C84.1 - 1995: American National Standard for Electric Power Systems and Equipment - Voltage Ratings (60 Hz),
* IEEE "Red Book" and "Green Book"
See you at ECN!
Scott
p.s. What's your handle at ECN?
- Status