Forums

Harmonics in pole power transformers?

Started by Joerg April 17, 2016
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/
On Sun, 17 Apr 2016 13:55:05 -0700, 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.
If the transformer fails, won't that stop power to the pump?
> >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?
The way people often pick up an AC trigger for a scope or something is to wrap a couple of turns of insulated wire on top of the ac-high insulated wire, and drive a high-impedance amp. Can you get inside the breaker box, or access a motor wire, free-air or inside a conduit? -- John Larkin Highland Technology, Inc lunatic fringe electronics
On 2016-04-17 14:00, John Larkin wrote:
> On Sun, 17 Apr 2016 13:55:05 -0700, 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. > > If the transformer fails, won't that stop power to the pump? >
Yup. The system is a mote network that then needs to send out an alarm. The pumps aren't always running and the alert should not go out when no power is drawn but mains power is available.
>> >> 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? > > The way people often pick up an AC trigger for a scope or something is > to wrap a couple of turns of insulated wire on top of the ac-high > insulated wire, and drive a high-impedance amp. Can you get inside the > breaker box, or access a motor wire, free-air or inside a conduit? >
That's exactly what we want to avoid. It's all outdoor stuff so even running a non-connected sniffer wire into the breaker box is frowned upon. -- Regards, Joerg http://www.analogconsultants.com/
On Sun, 17 Apr 2016 14:14:36 -0700, Joerg <news@analogconsultants.com>
wrote:

>On 2016-04-17 14:00, John Larkin wrote: >> On Sun, 17 Apr 2016 13:55:05 -0700, 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. >> >> If the transformer fails, won't that stop power to the pump? >> > >Yup. The system is a mote network that then needs to send out an alarm. >The pumps aren't always running and the alert should not go out when no >power is drawn but mains power is available. > > >>> >>> 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? >> >> The way people often pick up an AC trigger for a scope or something is >> to wrap a couple of turns of insulated wire on top of the ac-high >> insulated wire, and drive a high-impedance amp. Can you get inside the >> breaker box, or access a motor wire, free-air or inside a conduit? >> > >That's exactly what we want to avoid. It's all outdoor stuff so even >running a non-connected sniffer wire into the breaker box is frowned upon.
Is the feed open-wire on a pole? Who's doing the frowning? -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sunday, April 17, 2016 at 1:54:36 PM UTC-7, 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.
If you could depend on a little electric 'hum', maybe a microphone would do. Acoustic output from any inductor usually has a bit of 120 Hz, For that matter, maybe you could bypass the switch on the pump, with a safety-rated capacitor ad/or resistor, so there's always a small (1 mA) current, and do your acoustic sensing near the pump motor?
On Sun, 17 Apr 2016 15:08:07 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

>On Sunday, April 17, 2016 at 1:54:36 PM UTC-7, 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. > >If you could depend on a little electric 'hum', maybe a microphone would >do. Acoustic output from any inductor usually has a bit of 120 Hz, >For that matter, maybe you could bypass the switch on the pump, >with a safety-rated capacitor ad/or resistor, >so there's always a small (1 mA) current, and do your acoustic sensing near >the pump motor?
The pole that supports the transformer probably vibrates at 60 or 120 Hz. And I bet there's a healthy magnetic field near the transformer. The transformer will get a little warm when it's powered up, but that would be expensive to sense from a distance. Laser interferometer? That's not TOO silly. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sun, 17 Apr 2016 13:55:05 -0700, 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?
The pump doesn't know that the other side of the relay/switch has power ?>:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The touchstone of liberalism is intolerance
On Sun, 17 Apr 2016 13:55:05 -0700, 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?
Hmmm, I constructed a Tone probe using a LM386 as the receiver. It does a good job at pickingup 60 hz Hum. Maybe that loosly coupled with the AC input of the pump and a 555 as a missing pulse detector would work. Cheers
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. Jon
On Sunday, April 17, 2016 at 3:21:04 PM UTC-7, John Larkin wrote:
> On Sun, 17 Apr 2016 15:08:07 -0700 (PDT), whit3rd <whit3rd@gmail.com> > wrote: > > >On Sunday, April 17, 2016 at 1:54:36 PM UTC-7, Joerg wrote: > >> Folks, > >> > >> A system needs to be able to detect whether a pole transformer has > >> failed and stopped feeding power...
> >If you could depend on a little electric 'hum', maybe a microphone...
> The pole that supports the transformer probably vibrates at 60 or 120 > Hz. And I bet there's a healthy magnetic field near the transformer.
If the pump is turned on by a relay (NO), can you use the NC contacts on that relay to operate a humming object (like, another relay)? That'd give you an acoustic signature at the control box, far from the transformer. Heck, operate the alarm from the NC contacts of an always-on relay. Where DO you have access to the wiring and/or apparatus?