Harmonics in pole power transformers?

That's why they use aluminum windings (lower cost).

Efficiency is still rather high with huge overload tolerance, which means they're not running saturated before or even at full load.

Transformer cores saturate because of applied primary voltage, not load. In the end it's a compromise between copper costs and energy loss.

Are the power feeds to each transformer single wire by change, with a ground rod installed at each transformer pole for the return path?

If so, maybe you can snap a current transformer over the ground return and monitor things that way.

SWER? That's only used in the more remote places of Australia and NZ. Not here. It's always two-phase or three-phase via wires.

This is a tad confusing: the economic use of wire means you want to wrap it around a small core, and it's both volts/turn and the core size that determine saturation . And 'full load' means FAR FROM SATURATION, because the secondary current reduces the magnetization: iif saturation occurs, it will be at MINIMUM OUTPUT CURRENT conditions.

What the power company wants, is for the transformer losses on their side of the meter to be small. Don't expect saturation (it'll go away when the pump is on) and don't trust a sensor of harmonics unless you calibrate at all drive and load combinations.

Better, just don't trust harmonics; the zero-load hum of a transformer with a failed-open secondary will fool you.

Most distribution transformers "pole pigs" have a secondary circuit breaker. If your transformer has a short, stamped metal lever hanging off the side, with a hole near the end of the lever, that is the circuit breaker "handle". Larger transformers, like above 100 KVA generally don't have this, but at least in our area, most residential transformers do. The hole is so they can trip the breaker on and off from the ground with a hot stick. They use this to cut power if they need to work on your drop, change your meter or such work.

If that breaker trips, the transformer is still energized, but no connection from secondary to the service entrance.

(Info certainly applies in US, only.)

Jon

As far as I know, they don't use HV hot-hot much for residential. Most of the transformers have one HV terminal, and the housing is the ground return for the HV. I have seen in a FEW places transformers that had 2 HV terminals. These might have been on the truck for use in open delta setups, and that is all they had when they needed one for a repair.

Our whole neighborhood is all single phase feed, one hot HV wire with a big insulator, and then a ground. The main street has 7200 V and 45 KV 3-phase. The 45 KV feeds a substaion a mile or so away.

Jon

Sounds more like low-labor corporate or absentee owner situation. If it involved livestock, or even just irrigation, you'd need more operating info than just the power being present at a pump.

You could sell it to somebody at the corporate level - it doesn't have to make sense, if you convince them it will 'on average save......'.

RL

If you have mains power one small primary battery can run the transmitter, (eg 2xAA) repace after each use, else every few years.

It isn't that easy. This is all remote and ideally there should be zero installation effort beyond strapping it to some fence post, meaning no need for an electrician. Afterwards it shall run almost indefinitely without having to service a battery every few years.

Weird. I walk our dogs every morning here in Cameron Park (California) so today I double-checked: All transformers have two HV terminals. Most of my walking route is along streets that have three HV phases along the poles and the transformers are connected "round-robin" style to equalize the load, each between two phases. Then there are small HV tap offs to some clusters of homes with only two phases. But same transformers with two HV prongs.

Larger businesses have 3-phase transformers with three HV terminals.

Our utility is PG&E. Running a fourth wire for neutral somehow doesn't make sense from a cost POV. So they don't.

As I've said, such information is already being furnished. This whole topic is about furnishing an additional bit of information, mains power failure. Without needing an electrician to come out for the install.

It's not about big corp products either.

Neutrals are only developed at the final LV (

Jon was talking about the HV side, transformers with just one HV terminal. There you either need an extra HV neutral or SWER.

Sure I was.

...and you weren't.

RL

Joerg - have you had any luck finding harmonics charactoristic of power line transformers?

Hul

Joerg wrote:

PG&E may connect their distribution transformers phase to phase, but I assure you that many others connect them phase to ground.

No, we'll just be going after 60Hz for now but the system will be adaptable to doing 60Hz and 180Hz, allowing our own experiments.