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Harmonics in pole power transformers?

Started by Joerg April 17, 2016
On 2016-04-21 14:53, Cydrome Leader wrote:
> Joerg <news@analogconsultants.com> wrote: >> On 2016-04-17 16:39, Jon Elson wrote: >>> Joerg wrote: >>> >>> >>>> In order not to get fooled by 60Hz from other overhead lines I was >>>> wondering if classic pole transformers generate enough 3rd and 5th >>>> harmonics to distinguish the field emanating from secondary wires from >>>> that coming from overhead HV lines. Does anyone know where to find info >>>> about that? >>>> >>> Geez, I would expect there to be VERY little 3rd or 5th harmonic from a >>> transformer. These harmonics require a nonlinear response, and they >>> shouldn't be nonlinear. >>> >> >> All transformers are non-linear because there is an economical limit to >> the amount of copper they put on there. My question is just, how >> non-linear is the average pole transformer? > > 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. -- Regards, Joerg http://www.analogconsultants.com/
Joerg <news@analogconsultants.com> wrote:
> On 2016-04-18 18:55, Ralph Barone wrote: >> Joerg <news@analogconsultants.com> wrote: >>> Folks, >>> >>> A system needs to be able to detect whether a pole transformer has >>> failed and stopped feeding power to a pump. The transformer will be >>> 100ft or more away. The detection has to work even without any power >>> flow meaning we can only detect the presence of a 60Hz electric field >>> that leaks from the various boxs such as a breaker box. >>> >>> In order not to get fooled by 60Hz from other overhead lines I was >>> wondering if classic pole transformers generate enough 3rd and 5th >>> harmonics to distinguish the field emanating from secondary wires from >>> that coming from overhead HV lines. Does anyone know where to find info >>> about that? >>> >> >> I would assume that your classic "pole pig" uses similar iron to its big >> brother in the substation, and that it works at a similar flux density, >> therefore your proposal is likely to translate to "you can't get there from >> here". >> > > Well, I was hoping the substation transformers were much better because > there is not as much cost and size per kW pressure as with pole pigs. > But maybe that isn't the case. We shall see, only experiments will tell, > it seems. > > >> Why not just build your box to memorize the EMC environment when it is >> first turned on and compare to that. Then all you need is an instruction to >> not install your box on a dead circuit. >> > > That's what we'll do anyhow. But the fields from the power lines can > change in many locations even without faults. Swaying vegetation, > animals, precipitation, vehicle traffic and so on.
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.
On 2016-04-21 15:21, Cydrome Leader wrote:
> Joerg <news@analogconsultants.com> wrote: >> On 2016-04-18 18:55, Ralph Barone wrote: >>> Joerg <news@analogconsultants.com> wrote: >>>> Folks, >>>> >>>> A system needs to be able to detect whether a pole transformer has >>>> failed and stopped feeding power to a pump. The transformer will be >>>> 100ft or more away. The detection has to work even without any power >>>> flow meaning we can only detect the presence of a 60Hz electric field >>>> that leaks from the various boxs such as a breaker box. >>>> >>>> In order not to get fooled by 60Hz from other overhead lines I was >>>> wondering if classic pole transformers generate enough 3rd and 5th >>>> harmonics to distinguish the field emanating from secondary wires from >>>> that coming from overhead HV lines. Does anyone know where to find info >>>> about that? >>>> >>> >>> I would assume that your classic "pole pig" uses similar iron to its big >>> brother in the substation, and that it works at a similar flux density, >>> therefore your proposal is likely to translate to "you can't get there from >>> here". >>> >> >> Well, I was hoping the substation transformers were much better because >> there is not as much cost and size per kW pressure as with pole pigs. >> But maybe that isn't the case. We shall see, only experiments will tell, >> it seems. >> >> >>> Why not just build your box to memorize the EMC environment when it is >>> first turned on and compare to that. Then all you need is an instruction to >>> not install your box on a dead circuit. >>> >> >> That's what we'll do anyhow. But the fields from the power lines can >> change in many locations even without faults. Swaying vegetation, >> animals, precipitation, vehicle traffic and so on. > > 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. -- Regards, Joerg http://www.analogconsultants.com/
On Thursday, April 21, 2016 at 2:53:08 PM UTC-7, Cydrome Leader wrote:
> Joerg <news@analogconsultants.com> wrote:
> > All transformers are non-linear because there is an economical limit to > > the amount of copper they put on there.
> Efficiency is still rather high with huge overload tolerance, which means > they're not running saturated before or even at full load.
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.
whit3rd wrote:

> On Thursday, April 21, 2016 at 2:53:08 PM UTC-7, Cydrome Leader wrote: >> Joerg <news@analogconsultants.com> wrote:
> > 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
Joerg wrote:


> 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. >
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
On Tue, 19 Apr 2016 12:29:26 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 04/19/2016 12:19 PM, Cydrome Leader wrote: >> Joerg <news@analogconsultants.com> wrote: >>> On 2016-04-18 15:02, Lasse Langwadt Christensen wrote: >>>> Den mandag den 18. april 2016 kl. 23.50.56 UTC+2 skrev legg: >>>>> On Mon, 18 Apr 2016 07:58:30 -0700, Joerg <news@analogconsultants.com> >>>>> wrote: >>>>> >>>>>> On 2016-04-18 07:57, legg wrote: >>>>>>> On Sun, 17 Apr 2016 17:16:12 -0700 (PDT), George Herold >>>>>>> <gherold@teachspin.com> wrote: >>>>>>> >>>>>>>> On Sunday, April 17, 2016 at 4:54:36 PM UTC-4, Joerg wrote: >>>>>>>>> Folks, >>>>>>>>> >>>>>>>>> A system needs to be able to detect whether a pole transformer has >>>>>>>>> failed and stopped feeding power to a pump. The transformer will be >>>>>>>>> 100ft or more away. The detection has to work even without any power >>>>>>>>> flow meaning we can only detect the presence of a 60Hz electric field >>>>>>>>> that leaks from the various boxs such as a breaker box. >>>>>>>>> >>>>>>>>> In order not to get fooled by 60Hz from other overhead lines I was >>>>>>>>> wondering if classic pole transformers generate enough 3rd and 5th >>>>>>>>> harmonics to distinguish the field emanating from secondary wires from >>>>>>>>> that coming from overhead HV lines. Does anyone know where to find info >>>>>>>>> about that? >>>>>>>>> >>>>>>>>> -- >>>>>>>>> Regards, Joerg >>>>>>>>> >>>>>>>>> http://www.analogconsultants.com/ >>>>>>>> >>>>>>>> Magneto-striction causes the transformer to vibrate at 120 Hz, >>>>>>>> I don't know if you could sense that. >>>>>>>> >>>>>> >>>>>> Audio buzz isn't reliable here because the transformer will be far away. >>>>>> All we have is any E-field leaking out from conduit and the breaker box. >>>>>> The good thing is, we can be right at the breaker box, just not in it. >>>>>> >>>>>> >>>>>>>> George H. >>>>>>> >>>>>>> Transformers can fail and still buzz. >>>>>>> >>>>>>> There are many reasons why a pump might fail. Expending effort at >>>>>>> sensing just a single one of these is misdirected. >>>>>>> >>>>>> >>>>>> No, it is not. The fact that transformer or HV line failure is by far >>>>>> the highest concern in this application is based on clear statistical >>>>>> evidence. >>>>>> >>>>> I'd like to see THOSE statistics. >>>>> >>>>> You're trying to see if a pump is functional, when it's not supposed >>>>> to be running. Does this make sense to you? >>>> >>>> if it is, say, a pump to keep a basement from flooding or some cows from >>>> going thirsty it makes perfect sense to get an electrician out to fix the >>>> power before it is needed >>>> >>> >>> Bingo! >> >> No. It costs too much to hire electricians. The problem will have to fix >> itself. >> >> >If you're the farmer or building owner, it's reasonable. On the other >hand, if you're selling gizmos that will on average save several hundred >dollars' worth of wasted time every few years, you can charge more for >your gizmo. > >Everybody wins. What's not to like? > >Cheers > >Phil Hobbs
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
On 2016-04-21, Joerg <news@analogconsultants.com> wrote:
> On 2016-04-20 23:42, Jasen Betts wrote: >> On 2016-04-19, Joerg <news@analogconsultants.com> wrote: >>> On 2016-04-19 03:07, Jasen Betts wrote: >>>> On 2016-04-18, Joerg <news@analogconsultants.com> wrote: >>>>> On 2016-04-18 09:41, Adrian Tuddenham wrote: >>>>>> Joerg <news@analogconsultants.com> wrote: >>>> >>>>> That would require an electrician to come out and most would refuse this >>>>> job because they, their employer or their union won't allow non-standard >>>>> stuff. >>>> >>>> Yeah, and if they're paying a visit they could as easily install a >>>> standard electical outlet for you to plug your alarm into. >>>> >>> >>> The trick is to be able to install this without that truck roll. Because >>> such a truck roll would increase the cost per install by several hundred >>> Dollars, considering travel charges. >> >> yeah, but you save some that you'd otherwise have to spend on on cow-proof solar panels >> and batteries... >> > > You need those anyhow. How else would you convery a mains power failure?
If you have mains power one small primary battery can run the transmitter, (eg 2xAA) repace after each use, else every few years. -- \_(&#12484;)_
On 2016-04-23 02:08, Jasen Betts wrote:
> On 2016-04-21, Joerg <news@analogconsultants.com> wrote: >> On 2016-04-20 23:42, Jasen Betts wrote: >>> On 2016-04-19, Joerg <news@analogconsultants.com> wrote: >>>> On 2016-04-19 03:07, Jasen Betts wrote: >>>>> On 2016-04-18, Joerg <news@analogconsultants.com> wrote: >>>>>> On 2016-04-18 09:41, Adrian Tuddenham wrote: >>>>>>> Joerg <news@analogconsultants.com> wrote: >>>>> >>>>>> That would require an electrician to come out and most would refuse this >>>>>> job because they, their employer or their union won't allow non-standard >>>>>> stuff. >>>>> >>>>> Yeah, and if they're paying a visit they could as easily install a >>>>> standard electical outlet for you to plug your alarm into. >>>>> >>>> >>>> The trick is to be able to install this without that truck roll. Because >>>> such a truck roll would increase the cost per install by several hundred >>>> Dollars, considering travel charges. >>> >>> yeah, but you save some that you'd otherwise have to spend on on cow-proof solar panels >>> and batteries... >>> >> >> You need those anyhow. How else would you convery a mains power failure? > > 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. -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-22 15:21, Jon Elson wrote:
> Joerg wrote: > > >> 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. >> > 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. >
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. -- Regards, Joerg http://www.analogconsultants.com/