Forums

Harmonics in pole power transformers?

Started by Joerg April 17, 2016
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.
> Concentrate on the pump, not the power source. >
Not possible because that turns on and off automatically. Any attempt to log that relationship is expensive and requires an electrician to come out for installation and that is not desired. Many other reasons, too. -- Regards, Joerg http://www.analogconsultants.com/
On 2016-04-18 07:48, Phil Hobbs wrote:
> 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? >
We don't want to sense current, only the presence of 240VAC from the transformer. It is meant to alert the customer that they need to call someone from the utility to come out because either the HV line has gone dry or the transformer has failed. It would make no sense to send their own staff because they aren't allowed to work on anything up the pole or even before the meter box. These are remote installations where a truck roll is expensive no matter who has to come out. So if the wrong crew shows up they have a big cost wrote-off.
> 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. -- Regards, Joerg http://www.analogconsultants.com/
On Mon, 18 Apr 2016 07:41:45 -0700, Joerg <news@analogconsultants.com>
wrote:

>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.
Outside of a metal breaker box, there's no h-field with no current, and no e-field leaking out. The ambient e-field will be dominated by other stuff, like other circuits and light bulbs in the room. Maybe it can't be done. Suppose you had a small, coin-sized magnetized thing. Would you need an electrician to open the breaker box, stick it to the cover or the side inside, and close it? You don't need an electrician to open the box and flip breakers. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On 2016-04-18 08:32, John Larkin wrote:
> On Mon, 18 Apr 2016 07:41:45 -0700, Joerg <news@analogconsultants.com> > wrote: > >> 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. > > Outside of a metal breaker box, there's no h-field with no current, > and no e-field leaking out. The ambient e-field will be dominated by > other stuff, like other circuits and light bulbs in the room. >
There is no room. Just that last pole, the transformer, a meter and breaker box and the pumps. Other than that maybe some cattle. We'd be counting on the ever so small leaking E-field because with the pumps turned off that's all there is going to be. Hence my question whether we could use harmonics to see a change versus the E-field coming from the distant HV line. The engineer taking care of the software side is very good at extracting signature signals to hear "the grass grow".
> Maybe it can't be done. >
Possible. That's why we are engineers, to try out until we are 110% sure it truly can't be done. If it turns out it can be done the company has a leg up on the competition, big time :-)
> Suppose you had a small, coin-sized magnetized thing. Would you need > an electrician to open the breaker box, stick it to the cover or the > side inside, and close it? You don't need an electrician to open the > box and flip breakers. >
No, but many outdoor boxes have a gasket seal which you technically are not allowed to compromise. What we were mulling is a 2nd transmitter inside the box. But that would probably become a show-stopper. -- Regards, Joerg http://www.analogconsultants.com/
On 04/18/2016 10:58 AM, Joerg 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. > > >> Concentrate on the pump, not the power source. >> > > Not possible because that turns on and off automatically. Any attempt to > log that relationship is expensive and requires an electrician to come > out for installation and that is not desired. Many other reasons, too. >
As John says, you don't have a B field and the E field is shielded out by the box. How about gluing the sensor to the inside of the box, the receiver to the outside, and using two piezo buzzers to communicate? 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 Sunday, April 17, 2016 at 2:14:08 PM UTC-7, Joerg 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.
If the pumps aren't always running, what triggers the pumps to turn on and off? Would it be acceptable to determine that power has failed when the command to turn the pumps on fails? Michael
Den mandag den 18. april 2016 kl. 17.59.43 UTC+2 skrev mrda...@gmail.com:
> On Sunday, April 17, 2016 at 2:14:08 PM UTC-7, Joerg 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. > > > If the pumps aren't always running, what triggers the pumps to turn on and off? > > Would it be acceptable to determine that power has failed when the command to turn the pumps on fails? > > Michael
could be a simple mechanical float switch? how about at small load at the pump and a current sensor? maybe the load could a powersupply for something that injects a lf/hf on to the line that you can detect at the box? -Lasse
On Monday, April 18, 2016 at 9:22:14 AM UTC-7, Lasse Langwadt Christensen wrote:
> Den mandag den 18. april 2016 kl. 17.59.43 UTC+2 skrev mrda...@gmail.com: > > On Sunday, April 17, 2016 at 2:14:08 PM UTC-7, Joerg 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. > > > > > > If the pumps aren't always running, what triggers the pumps to turn on and off? > > > > Would it be acceptable to determine that power has failed when the command to turn the pumps on fails? > > > > Michael > > could be a simple mechanical float switch?
Oh! Good idea. I thought it was something electrical, powered by something else.
> how about at small load at the pump and a current sensor?
That is a good idea too! With a circuit in parallel with the pump, keep a lead-acid battery charged, or a supercapacitor. When power fails, send the owner a text message or something.
> maybe the load could a powersupply for something that injects > a lf/hf on to the line that you can detect at the box? > > -Lasse
:D Michael
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.) -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
On Mon, 18 Apr 2016 07:52:30 -0700, Joerg <news@analogconsultants.com>
wrote:

>> 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>
>Their cores all saturate a little. I only need to know how much that is >with pole transformers.
Offhand, I can see some problems with using harmonics: 1. Most of the distortion (harmonics) are cause by non-linear loads, over which you have no control. Worse, they vary. If you can see transformer induced harmonics under all that junk, I would be impressed by your DSP programming. 2. Core saturation is a function of load current, which can vary. I suspect that the distortion is much less with a light load, than with a heavy load. If the transformer fails while it is lightly loaded, you probably won't see a change. 3. Increased distortion from core saturation is only a function of perhaps one failure mode, over current. There are plenty of other failure modes, such as coolant loss, various leakage faults, phase balancing, space weather, etc that do not necessarily generate a corresponding increase in distortion. 4. Grid tied (solar) generators are really noisy and tend to produce harmonic spikes on the power lines. The better inverters have line filters to reduce the problem, but most do little or nothing. 5. HomePlug and various carrier current communications schemes apply RF onto the line. While this is unlikely to affect low order harmonics of 60Hz, it still should be considered and tested. 6. If you put your finger on the probe tip of your oscilloscope, you'll see a fair approximation of the type of junk found on power lines. Seeing small changes in harmonic content is going to be difficult.
>> 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.
It's more reliable than trying to detect xformer distortion. If your purpose is to anticipate a transformer failure, there's nothing better than temperature. Think about attaching a stick on label that changes color at some critical temperature: <https://en.wikipedia.org/wiki/Thermochromism> Or just slop some thermochromatic paint on the xformer case. HV line failures and fuse failures will produce an instantaneous loss in xformer output voltage. I would think you could by just monitoring the local line voltages and waveforms. Back when I was building server farms, we were learning all about reliable power. PG&E would pay for damaged equipment, but it was my responsibility to prove that they screwed up. So, we invested in power line impairment equipment. As I recall, it was made by Dranetz, but I don't recall the model. It gave us a paper tape printout of just about anything that might go wrong on the power line. It paid for itself in about 4 years and inspired PG&E to replace some failing equipment. I still do some of that at various mountain top radio sites. This is probably overkill for what you need, but comes close to what you're trying to detect. It might be useful to look at some of this equipment, see what they can detect, determine how they do it, and see if it can be used. If you invent a new method of doing all that by induction or no wire contact, I want to invest in the company. <http://www.dranetz.com/power-quality-analyzers/> <http://en-us.fluke.com/products/power-quality-analyzers/> <https://www.google.com/search?q=power+quality+analyzer&tbm=isch> -- 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