Forums

Harmonics in pole power transformers?

Started by Joerg April 17, 2016
On 2016-04-18 09:41, Adrian Tuddenham 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? > > Put a small strip of double-sided PC board between the power conductors > coming into the breaker box and wrap earthed foil around the outside of > the conductors for a short distance each side of it. A high-impedance > differential op-amp would detect the voltage difference between the two > sides of the board when there was a voltage difference between the two > conductors, but would be unaffected by common-mode voltages or an > external field. > > (With slightly changed geometry, this could be used as an undetectable > telephone-tapping device.) >
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. -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-18 12:35, Joerg wrote:
> On 2016-04-18 10:43, jrwalliker@gmail.com wrote: >> On Monday, 18 April 2016 16:42:56 UTC+1, Joerg wrote: >> >>> There is no room. Just that last pole, the transformer, a meter and >>> breaker box and the pumps. Other than that maybe some cattle. >> >> If the meter is an old electro-mechanical one there will probably be >> a useful B field leaking from the voltage winding, even when >> there is no load. >> > > Now that is a good idea! As long as there is a meter. >
Do you know if the new smart meters also leak enough B-field to be detectable at close distance? [...] -- Regards, Joerg http://www.analogconsultants.com/
On Mon, 18 Apr 2016 13:21:07 -0700, Joerg <news@analogconsultants.com>
wrote:

>On 2016-04-18 12:35, Joerg wrote: >> On 2016-04-18 10:43, jrwalliker@gmail.com wrote: >>> On Monday, 18 April 2016 16:42:56 UTC+1, Joerg wrote: >>> >>>> There is no room. Just that last pole, the transformer, a meter and >>>> breaker box and the pumps. Other than that maybe some cattle. >>> >>> If the meter is an old electro-mechanical one there will probably be >>> a useful B field leaking from the voltage winding, even when >>> there is no load. >>> >> >> Now that is a good idea! As long as there is a meter. >> > >Do you know if the new smart meters also leak enough B-field to be >detectable at close distance? > >[...]
The ones with a rotating disk sure do. Pure electronic ones might have a small power transformer, might not. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Den mandag den 18. april 2016 kl. 22.28.58 UTC+2 skrev John Larkin:
> On Mon, 18 Apr 2016 13:21:07 -0700, Joerg <news@analogconsultants.com> > wrote: > > >On 2016-04-18 12:35, Joerg wrote: > >> On 2016-04-18 10:43, jrwalliker@gmail.com wrote: > >>> On Monday, 18 April 2016 16:42:56 UTC+1, Joerg wrote: > >>> > >>>> There is no room. Just that last pole, the transformer, a meter and > >>>> breaker box and the pumps. Other than that maybe some cattle. > >>> > >>> If the meter is an old electro-mechanical one there will probably be > >>> a useful B field leaking from the voltage winding, even when > >>> there is no load. > >>> > >> > >> Now that is a good idea! As long as there is a meter. > >> > > > >Do you know if the new smart meters also leak enough B-field to be > >detectable at close distance? > > > >[...] > > The ones with a rotating disk sure do. Pure electronic ones might have > a small power transformer, might not. >
don't many of the electronic ones have an IR interface so you can just ask it if it is on? -Lasse
I don't understand the quesiton...

seems you just want to know if the supply voltage is there, or not there?

why all the stuff about harmonics?

M


Den s&#2013266168;ndag den 17. april 2016 kl. 22.54.36 UTC+2 skrev Joerg:
> 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/
electrical-testers/fluke-2ac-electrical-tester.html ? -Lasse
On 2016-04-18 14:11, makolber@yahoo.com wrote:
> I don't understand the quesiton... > > seems you just want to know if the supply voltage is there, or not there? >
Yup, without contacting anything or breaching any enclosure.
> why all the stuff about harmonics? >
The idea was to sense an E-field but in order to distinguish the transformer output E-field from older 60Hz fields rely on the harmonics that naturally occur because there will be some core saturation. Not sure if that difference is strong enough which is why I asked here. -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-18 14:19, Lasse Langwadt Christensen wrote:
> Den s&#2013266168;ndag den 17. april 2016 kl. 22.54.36 UTC+2 skrev Joerg: >> 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/ > > electrical-testers/fluke-2ac-electrical-tester.html >
http://en-us.fluke.com/products/electrical-testers/fluke-2ac-electrical-tester.html#resources It doesn't let me download the manual but from the pictures it looks like you need to be closer than an inch. -- Regards, Joerg http://www.analogconsultants.com/
On Monday, April 18, 2016 at 4:09:48 PM UTC-4, Joerg wrote:
> On 2016-04-18 09:41, Adrian Tuddenham 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? > > > > Put a small strip of double-sided PC board between the power conductors > > coming into the breaker box and wrap earthed foil around the outside of > > the conductors for a short distance each side of it. A high-impedance > > differential op-amp would detect the voltage difference between the two > > sides of the board when there was a voltage difference between the two > > conductors, but would be unaffected by common-mode voltages or an > > external field. > > > > (With slightly changed geometry, this could be used as an undetectable > > telephone-tapping device.) > > > > 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. > > -- > Regards, Joerg > > http://www.analogconsultants.com/
I'm not sure what requires an electrician. But can't you stick some similar gizmo around the wires going to the pump and sense the E-field. (I guess if it's coax it's a lot harder.) George H. (Who needs to call his electrician.)
On Monday, April 18, 2016 at 8:02:21 AM UTC-7, Joerg wrote:
> On 2016-04-18 07:48, Phil Hobbs wrote:
> > I'd be wanting to move the goal posts and cycle the pump every few hours > > just to make sure.
> We can't. It's all automatic and often legacy equipment that some might > even call pre-historic.
Just for giggles: is there a meter on these drops? A smart meter, that takes 3W all the time, that has wireless reporting back to the utility? If you could read out the meter, it'd solve the problem instantly.