Re: Stray Neutral Current along Wye distribution lines
Derek,
Arizona Public Service Co. is our local service provider. Costs of any changes in this local area to reduce ground current are proposed to APS to be born by the property owners. APS is one of the the largest power providers in the state and has a healthy bottom line at present. In fact the corporation commission reduced rates recently. So this isn't a case of expecting something for nothing from a "poor starving" power co., and frankly billions over a decade or so wouldn't be $1 on the power bill. We just need to start figuring out the solution, and a way to phase it in sanely. Based on more recent studies, we'll all come out ahead financially by dealing with it. Medical costs are skyrocketing.
I understand that the earth is a "free" conductor. Alas, it's not free to those affected by ground current and there are few places left to avoid it. Those who do EMF mitigation work have met some good folks whose lives have been profoundly affected. I think if we put our heads together, we could come up with a workable solution.
What I'd like to do is come up with a practical and safe grounding approach that could be used in rural areas around folks with serious health problems aggravated by ground current. What I've seen here is that even slow growth of the power service area has increased ground current significantly. Only near the very end of service lines is it avoidable, and alas the ends keep moving on. The same people who can't handle the constant low level magnetic fields from ground current are usually chemically injured and can't use propane, making off grid living impractical.
Some of your statements also have me confused. In areas where secondary distribution lines are delta, it's my understanding that two hot wires (single phase and 10KV in this area) are run instead of the 7.2KV line and neutral and therefore at the delta 220V secondary, the center tap is earthed to provide a ground. If this is safe and widely used, what's wrong with using the same (secondary derived neutral) approach elsewhere?
According to my local APS supervisor, some of his service area lines are in fact wired as delta- two hots and no neutral on the poles, with a site (secondary) derived neutral.
This is exactly what I'd like to do in this area, "pretending" that the neutral is a hot phase, but using it for the TVSS connection to the secondary winding.
In this setup, the tranformer secondary is earthed twice, once at the transformer (powerco), and then at the meter panel. These will not cause a big net current problem and there will be no net current induced on the transmission lines. Powerco guys sometimes forget that a transformer will stop net current (another form of ground loop), if only it is NOT jumped around by the "ground tie". It really does, we EE circuit designers with some EMC background use it all the time in analog and communications circuit design. The physics don't change just because the the scale is much larger.
Ground rods for lightning and surge protection along the power lines could certainly be used with TVSS devices instead of hard wiring, and without introducing much ground current (they would generate some capacitive losses)- but the need for constant grounding of the neutral phase seems more like a bad compulsion than science. And I just don't understand how it enhances safety, though I'd like to!
I think your balanced line concept (which I'd like to hear more about) sounds to me like what I know as a delta distribution. Delta is all the same phase, and only a single voltage normally no neutral, though some delta systems have one leg grounded, to further confuse things.
Bruce McCreary
