Fault location for distribution meshed networks (high density LV networks with multiple sources). High impedance fault location and trip on distribution OH lines. Optimal operation of micro-grids, impact of DER penetration, DER hosting capacity etc. Try to spend some time with your local utility, you will find more opportunities since they likely reduced their R&D budget the last few years.
DER penetration - the impacts of large amounts of solar (residential and commercial) and wind penetration
Impacts due to large adoption of electric cars. A few electric cars is a non-issue. Large adoption will require a lot of system upgrades. A lot. Depending on the charge interval, they pull several households of power during recharge.
Unique applications of 61850 communication assisted schemes.
Reliability engineering and asset management.
Energy storage
Synchophasor monitoring of the during disturbances or using synchrophasors for protection
Zero sequence of transmission lines. I tried to figure it out once, and was overcome by the complexity. Most of what people use is referred to as Carson's equations, but if you pull up a copy of Carson's paper, it provids un-derived equations that jump to results that I have never seen proven. Furhter, what are typically called Carson's Equations appear to actually be equations out of 1930's text by Wagner and Evans, and which then ended up in the famous WH T&D reference text, but if you look at the equations in the latter 2 sources, I see no way to compare to the equations in the old Carson paper. I sometimes think people are adjusting the "ground resistivity" fudge factor in the Zo equations till they get answers that match what they see in real faults, and then say the equations are correct. Maybe the major T-line software mfrs (Cape, Aspen) have papers that somehow prove their equations, but I think they treat their equations as a trade secret. I think it would be good if someone could really prove for public domain some good Zo equations that can model the side issue of showing current distribution in the ground. I found a guy that said he could prove Carson's equations once using an infinite Fourier series, but when I looked his results, I was lost but it looked to me it has a problem with showing current distribution in the ground.
Oh, come on John. There is no single value for zero sequence impedance of a line. The degree to which Carson's equations are approximated is a minor nit compared to the unknown/unknowable value of ρearth. To say that we need to know Carson's value to that degree is to completely ignore the fact that a line will have a range of impedances over the course of a year far greater than the uncertainty of that part of the equation. In practical terms, an empirical derivation of the line impedance during the wettest time of the year serves well. I've found that a ρearth value of 10 gives much better results here than the assumed value of 100.
Of course, it's not just the line either; the presence of distribution neutrals and other grounded conductors in the vicinity of the line all help make the actual value rather fuzzy.
Maybe we should all have two values of Z0, wet and dry. Set zone 1 based on the wet impedance but make sure that zone 2 still overreaches for the dry value.
"Oh come on John". Hmmmm, Oh well, I will move on past what sounds like a bad attitude or an anger of some sort.
My suggestion was related to the fun of a young and bright mind fully understanding the physics of magnetics fields with earth and ground wire return, well enough to finding a set of equations that show the electric and magnetic fields around a transmission line. If all you need is the mundaneness of saying there are too many variables for even the most accurate model to know what is going on, and Carson's equations (or whatever Aspen and Cape are doing) are just fine cuz you can plug in p.earth till you get Zo results that more or less match what you see in the real world, OK, then I am glad you (and 99.9% of the power engineering world) are satisfied.
However, that does not solve my curiosity, and I wish I was a young guy with a big puzzle in front of him and a chance to show how strong and bright I was by figuring out a cool massive puzzle that I used to dream I was bright enough to figure out. If you really want to know current distribution and magnetic and electric field distribution, you are not going to get it from Carson's equations. I assume you next will roll your eyes and say, "Oh come on John" and say only finite element analysis will do that. Maybe true, but I want more than that answer.
No, I'm pretty sure finite element analysis won't do it either. I see it as a problem with one equation and multiple unknowns (unknownables even).
I'd love to have single, calculable, value of Z0 for each of my lines. That would be a wonderful improvement over the present situation. No doubt what so ever. But should it be the March 15th impedance or should it be the August 31st impedance? Or, maybe the impedance on a balmy May afternoon?
Would it be the current distribution in the earth alone? Or, should it account for all of the current that returns above the earth in distribution neutrals? What about other linear conductive paths such as communication messenger wires. Railroad tracks can confuse the equation.
It would be a great academic exercise, thus perhaps a good PhD project, but I don't see it providing useful information as to how I should be setting my relays.
No anger or bad attitude. We had similar discussions over a decade ago and have just picked different windmills to tilt at.
