Forums

Harmonics in pole power transformers?

Started by Joerg April 17, 2016
On Sun, 17 Apr 2016 13:55:05 -0700, Joerg <news@analogconsultants.com>
wrote:

>A system needs to be able to detect whether a pole transformer has >failed and stopped feeding power to a pump.
This is what the utilities use: <http://www.gridsense.com/solutions-products/transformer-monitoring/> I don't think it will help you much since it is connected directly to the transformer, but might help to know what they're looking for. POWER SYSTEM HARMONICS. A Reference Guide to Causes, Effects and Corrective Measures. <http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/mvb-wp011_-en-p.pdf>
>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?
<https://en.wikipedia.org/wiki/Harmonics_(electrical_power)> Unfortunately, that's for conducted harmonic content, not radiated. Also, the load has to become seriously unbalanced and non-linear, which puts the transformer core partly into saturation due to increased currents, before it will start generating harmonics. Suggestion: A failing transformer usually like to overheat before boiling the cooling oil and exploding. I would think an IR thermometer and telescope would work to detect overload type failures. However, it won't do anything if the line is simply cut and the power goes away. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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. George H.
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. > >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. Concentrate on the pump, not the power source. RL
On 2016-04-17 15:02, John Larkin wrote:
> 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? >
I don't quite understand that question. It's the usual, two 10-12kV wires string along on poles, a transformer, and a 240VAV two-phase drop of 100ft down to the pumps. They like to keep that last pole with the transformer away that far to minimise it being damaged by trucks, farm equipment and such.
> Who's doing the frowning? >
The customer. They want a solution they can crack out of a package and stick to the outside of the breaker box or somewhere around that. No wiring. Doing anything inside a breaker box legally requires an electrician to come out and that's not desired because of the high cost. -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-17 15:08, whit3rd 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? >
No wiring desired and acoustic is too prone to false alarms. Has to be very robust. -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-17 15:38, Jim Thompson 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. >> >> 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 ?>:-} >
The pump does but the operator being far away does not. If no power the pump simply won't come on and that's a problem (after a while). -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-17 15:48, Martin Riddle 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. >> >> 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. >
Tone probe would be one of my ideas as well. I'd have top find some cheap and most of all small IC that fishes out 60Hz plus maybe 180Hz. We've got a uC and ADC but it might become overwhelmed with all the other noise if there isn't at least some filtering. Passive filtering is out because of the inductor sizes. Oh, and it has to literally sip power, micro amps. -- Regards, Joerg http://www.analogconsultants.com/
On 04/18/2016 10:42 AM, Joerg wrote:
> On 2016-04-17 15:08, whit3rd 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? >> > > No wiring desired and acoustic is too prone to false alarms. Has to be > very robust. >
I'd have to concur that a system like that might very well give a false sense of security. If you're not drawing any current, how do you tell whether you've got an open, e.g. from a burned relay contact, a blown transistor, or a cracked trace? I'd be wanting to move the goal posts and cycle the pump every few hours just to make sure. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
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? -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-17 17:15, Jeff Liebermann wrote:
> On Sun, 17 Apr 2016 13:55:05 -0700, Joerg <news@analogconsultants.com> > wrote: > >> A system needs to be able to detect whether a pole transformer has >> failed and stopped feeding power to a pump. > > This is what the utilities use: > <http://www.gridsense.com/solutions-products/transformer-monitoring/> > I don't think it will help you much since it is connected directly to > the transformer, but might help to know what they're looking for. > > POWER SYSTEM HARMONICS. A Reference Guide to Causes, Effects and > Corrective Measures. > <http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/mvb-wp011_-en-p.pdf> > >> 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? > > <https://en.wikipedia.org/wiki/Harmonics_(electrical_power)> > Unfortunately, that's for conducted harmonic content, not radiated. > Also, the load has to become seriously unbalanced and non-linear, > which puts the transformer core partly into saturation due to > increased currents, before it will start generating harmonics. >
Their cores all saturate a little. I only need to know how much that is with pole transformers.
> Suggestion: A failing transformer usually like to overheat before > boiling the cooling oil and exploding. I would think an IR > thermometer and telescope would work to detect overload type failures. > However, it won't do anything if the line is simply cut and the power > goes away. >
That's too iffy in terms of reliability. Also, we need to catch HV line failures and primary fuse failure as well. -- Regards, Joerg http://www.analogconsultants.com/