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rockrat
11-28-2010, 01:25 PM
I need a device to record the power fluctuations that I am still seeing at the house. The issue started in August with a lightening strike down the road. Ever since I have been getting all sorts of electrical interference and two local businesses have told me they had to buy new cash registers since then. Discussions with the local electrical distribution company have proved useless.

Today I witnessed the first power surge that I have seen since moving here 11+ years ago. It nearly screwed up the computer even though I have a ups installed for the system. The ups kicked in and cut direct power to the system but the battery was too low (old) and allowed the computer to power cycle. After booting the install cd and running a few tools I was able to get the system running again. I feel lucky that I was in the bathroom where I saw the light bulbs get very bright all the sudden and then heard the ups screaming for me to hit the reset button.

I realize that I have two issues today. First, I need to address the ups. I am doing that now. Second, I have now decided to record some data and take it to my local government, the electrical provider and the puco (not that they really care) and see if I can get the pot stirred up a bit.

So what I need is a device to record the power fluctuations that are entering my house and shop. A place I once worked owned one and we used it to get the power company there to fix a surge issue. But I cant remember who the maker was.

I can run an o-scope and diagnose different things but designing a recording device for this issue is a bit out of my league. I might be able to achieve the goal but it might take me quite a bit of time to do so.

I can run a Google search and find all sorts of devices but I dont know what is good and what is worthless. Can anyone that has used such a device point me in the right direction? Thanks a million.

rock~

squirrel
11-28-2010, 01:44 PM
Sounds like you lost your ground and have a 220V electric drier or well pump hooked up.

Do you have 2 ground rods in and are the connections good?
If they are good pull the meter from the base and check your ground lug on the inside(you might have to call your electric company to cut the seal)
Look out on the poles with binoculars and verify the ground is intact.

The scope will not do you any good, you will need power quality analyzer. These typicaly cost around $20,000 ++ new, you can get a used one for around $5k
Dranetz makes a good system, Power Platform, its available from Graingers.

Stuart Br
11-28-2010, 01:52 PM
Do you have an instrument hire shop close by? As mentioned previously a quality power analyser is very expensive to purchase, but it may make sense to hire a unit for a couple of weeks. This will come with calibration, so you will have a definitive record to supply to your power company.

SDL
11-28-2010, 01:53 PM
Should be able to get something like this

http://www.fluke.com/fluke/uken/power-quality-tools/three-phase/fluke-430-series.htm?PID=56078

Should be able to hire one.

Steve Larner

Paul Alciatore
11-28-2010, 02:23 PM
Since you are already looking for a better UPS, may I suggest that you look for one with source power monitoring capability. Here is but one example, not particularly a recomendation but just the first one I found:

http://www.cdw.com/shop/products/default.aspx?EDC=068311

It can be connected to a computer and the Voltage readings can be viewed with accompanying software. This essentially gives you the power monitoring ability. Two for one (UPS and power monitor).

Other specs you may want to investigate is the speed with which it can switch to battery power and the degree that it can surpress spikes.

The Artful Bodger
11-28-2010, 02:26 PM
I think with a few components and a bit of initative you could use your PC sound card to make a continuous recording of phase and voltage fluctuations.

Rosco-P
11-28-2010, 02:39 PM
If you can't determine the cause yourself, you might have to resort to an electrical firm which deals with utility power issues. For meaningful measurement and monitoring you want one of these: http://www.dranetz-bmi.com/ Buy one, maybe lease one or hire in a company to install one and interpret the results.

Forrest Addy
11-28-2010, 04:19 PM
Better have someone check for an open neutrals on your whole neighborhood's string of 11KV fed distribution transformers.

If you don't have a continuous current carryng path to the center tap of the pole transformer the load neutral can shift with the load unbalance as much as 40 volts. If lights dim on one side of your house and flare up on the other that's almost a sure sign on an open neutral. This kind of electrical fault aint just an annoyance. It can cause house fires.

Tom Curlee
11-28-2010, 04:35 PM
There is a Simpson Electric recording voltmeter on ebay that records the voltage (and current) on a strip of paper. They are asking $30. This might do what you need, although it might not record fast transients.



Tom

Tom Curlee
11-28-2010, 04:36 PM
There is a Simpson Electric recording voltmeter on ebay that records the voltage (and current) on a strip of paper. They are asking $30. This might do what you need, although it might not record fast transients.

http://cgi.ebay.com/Simpson-Multicorder-Model-604-Recording-Volt-Amp-Meter-/220701094268?pt=LH_DefaultDomain_0&hash=item3362cf717c

duckman
11-28-2010, 04:37 PM
You should be able to have your power comp. install a monitor for a week or 2 that will record for 24 / 7. Growing up we would get low power every afternoon , power comp. put on a monitor and it showed low power about 4 PM everyday , it was tire retreading co. 3 miles away turning on his tire cookers , they installed some new transformers problem went away.

darryl
11-28-2010, 04:53 PM
Go as far as you can with your own system first. Make sure all your neutrals in the panel are tight, including the incoming neutral. That won't help if it's a neighborhood-wide problem, but there is a good possibility that it will help. It's not uncommon for all those connections to become a bit loose. I hesitate to recommend that you tighten the incoming hot leads simply for your own safety, but it's something I would do.

If you're bent on recording the variations, you'll need a chart recorder of some type. An option might be to try to find an 'event' recorder, which in some configurations would simply give a count for each time an 'event' occurred. In this case, the event would be any time the voltage on either hot exceeded the norm. A simple electronic circuit would pulse the counter each time the voltage rose above, say 170 peak, something like that. All you'll get from that is a count, showing how many times the limit was exceeded. I don't know if there's much value to that, or if you can use it against the power company. They would probably only trust their own equipment, and it's unlikely they would want to install a chart recorder even temporarily.

If you're in an area where there are frequent damaging voltage surges, you might be better off to see about getting a proper surge protector installed in your panel. I'm not sure what the configuration it, but it could well be a custom main breaker, designed for a fast cutout in case of a surge. I don't really trust the surge protectors available to the consumer, but sometimes they do offer an equipment replacement guarantee with the better ( and more expensive ) ones.

gundog
11-28-2010, 05:21 PM
I have worked in the electric utility industry for more years than I want to admit. Your best bet is to call your Electric provider and insist on a recording volt meter placed at your house. This is not a house meter this will record voltage fluctuations over a period of time & plot it against current draw the old ones had paper graph wheels but the newer ones are computer based.

If they refuse to do this let them know you are filling a PUC complaint I am sure you will get one. They will leave it up for anywhere from 1 day to a month. Ask to see the results when they have downloaded it. Voltage is allowed to fluctuate +- 5% so for 120v 114v to 126v I believe this is the industry standard at least it has been for both companies I have worked for.

Good luck Mike

Arcane
11-28-2010, 06:00 PM
Your best bet is to call your Electric provider and insist on a recording volt meter placed at your house.

X 2. I worked for 16 years as a District Operator for the provincial electric utility and we did this quite often when we had a customer with an electrical problem. Sometimes it was our problem but much more often it was a customers wiring problem. Since you have two neighours who have experienced problems after the lightning strike, that tells me it's a pretty good chance there's a problem on the source side. More than likely the lightning strike has resulted in a neutral connection becoming compromised somewhere in the system. Your utility has a duty to provide "quality control" and there are standards that have to be met by the utility...maximum outages per month, maximum voltage high/low limits, maximum number of time voltage can be outside that. If your utility doesn't want to get off their collective butts, do as gundog said and don't take no for an answer.

J Tiers
11-28-2010, 06:41 PM
First thing I would do, before anything else, is to go to the grounding electrode conductor (the one going to the rod or water pipe etc), and hang a clamp meter on it.

If that reads "zero", I'd probably not believe it, and suspect a problem somewhere.

if it reads a LOT of current, you may have a neutral issue in your drop or in the service box in the house. I'd be very careful of unbalanced loads in the meantime, until that gets fixed.

A windstorm knocked a tree onto our drop a few years ago. Severed the neutral, and we were inadvertantly using the neighbor's neutrals for a week or two until they got the big problems fixed and came around to us. I saw 5A to 8A in the ground wire and water pipes (our ground IS the pipes) until it was fixed. Now it is no more than an amp or so when I last checked after the fix.

A lightning strike could have damaged the neutral connection for your local transformer, and voltages may be fluctuating as the load balance changes. We also had a neutral problem in the drop when we moved in here, and we had all sorts of blinking and dimming until we called up the powerco..... they had it fixed within 12 hours, they didn't want the liability for a bad neutral in the drop.

whitis
11-28-2010, 07:10 PM
Try to get the power company to supply a monitor. If you have notified them of a problem and asked for them to supply one and they don't, that is negligence and increases their liability.

You can get multimeters that will hook up to a computer. Uni-T UT71A is one example. Make sure the software is capable of logging and graphing the results unless you are up to writing your own. You can also get more expensive models that have data logging built in. You can only monitor one parameter and on one leg of the line at a time this way.

If your UPS and software have data logging capability, you can use that.

If you have a bad neutral, it can destroy equipment, lights, cause things to catch fire, etc. Stuff that can handle 110-220V without changing jumpers or switches will probably survive.

lakeside53
11-28-2010, 08:44 PM
Definitely check your own panel incoming power connections for tightness, and if alumium service wire, evidence that anti-oxidant coating was applied. Be careful - the only way to kill the power is to remove the meter, that that typically has a security lock tag on it.

I recently installed a "whole house" surge protector. Levitron Brand - about $220 list; $180 mail order. It's an external box that's wired to your panel Ground / Neutral bar, and to a 240v 20 amp breaker - and the breaker can be already in-use.

J Tiers
11-28-2010, 08:56 PM
I recently installed a "whole house" surge protector. Levitron Brand, about $180 mail order. It's an external box that's wired to your panel Ground / Neutral bar, and to a 240v 20 amp breaker - and the breaker can be already in-use.

it's a good plan..... but not perfect for surges. I still say it should be done, but.... the power capability of the units is limited, and above the rated power they get disconnected, becoming irrelevant, just like auto brakes that "break off" if applied too hard.

1) the thing typically contains big MOVs. The tolerances on an MOV are HUGE, as is the variation of voltage with current, and they do not typically protect tightly within a useful range aside from knocking down spikes to "only" several hundred volts. How MANY hundred volts is only roughly known.

2) To pass more recent UL standards requirements, they have to be current limited with a fuse and/or temperature protector..... at best, they will protect only up to the rating of the breaker they are on. Above that current, they are gone, and the voltage on all other circuits keeps heading higher.

3) alternate more accurately calibrated types of protector that can be used inside the devices are typically much lower rated as far as current, and probably still have an MOV in parallel as a protector for them, and may have a series power limiting protector as well.

CCWKen
11-28-2010, 09:23 PM
Sounds like a local regulator going bad. There's one up the road from here that went bad but the other way. I was getting 105-108 volts at tested outlets. One call and about four hours later, it was fixed. Our PUCO must have more clout in Texas. A letter to them will usually stir up a couple of CPS supervisors with a face-to-face meeting and at least two repair crews. All it usually takes is a call to the City Public Service's 800 number. Just a couple of months ago, a driver in a pickup truck took out a pole two blocks away. The electric went out at 10pm. They had a new pole and power restored in two hours. And I'm in a rural area.

bborr01
11-28-2010, 09:36 PM
I had a similar problem at my cottage. Lights dimming and getting real bright.

I called the power company and they sent someone out.

The guy connected a box to the lugs in the meter socket and said I had an open ground.

He tightened the ground and it has been fine since.

Brian

rockrat
11-28-2010, 10:13 PM
Thanks all. I have a list and I will be working though it tomorrow before I start making calls. I did recheck the grounding on my side today worried that it might be compromised.

I do like the recording device. Thanks for the link.

rock~

J Tiers
11-28-2010, 10:20 PM
"grounding" is really not the issue.

The issue is the integrity of the neutral from your place back into the transformer. The ground check I suggested is a check on the neutral, not the ground.

bborr01
11-28-2010, 10:46 PM
To make a correction on my posting #20.

The power company guy said I had an open common, not ground.:o

Brian

rockrat
11-28-2010, 11:37 PM
"grounding" is really not the issue.

The issue is the integrity of the neutral from your place back into the transformer. The ground check I suggested is a check on the neutral, not the ground.

Fair enough. My thought after typing the inital post was to double check my grounding. I mearly mentioned it in the last post as something I did today between now and then.

rock~

Evan
11-29-2010, 01:20 AM
I worked with the power company for over two decades. Number one, they don't trust anything except their own equipment to prove an issue with power. The only exceptions to that are the very top of the line power monitors made by people like Dranetz. For that reason we had two $8000 Dranetz power analyzers in the BC branch that we could bring in and use to figure out where problems were coming from.

If you show them a trace from a 30 dollar monitor they will just shake their heads and leave. I just had the guys out to check the pole pig and make sure everything is good. Since the fires this last summer the power has been very flaky with a lot of fast voltage changes. They aren't out of range but the voltage is fluctuating up and down some times several times per second as much as 5 volts. That is enough to make lights flicker and is annoying as hell.

When they came out they pronounced everything just fine and explained that they don't care and are not even equipped to measure fast fluctuations of the power. The only care about the average voltage over a five minute period.

J Tiers
11-29-2010, 09:06 AM
Number one, they don't trust anything except their own equipment to prove an issue with power.

That is a fact.

As far as the powerco is concerned, anything you have is inaccurate and probably dangerous. And you are a complete idiot whose every statement is stupid and can be ignored.

They have considerable evidence in favor of that opinion, so it is best to go along with it.

They DO usually believe that a 'civilian" can correctly identify blinking lights. Anything past that and whatever YOU say is ridiculous. Just go along with it, and have them check it if you think there is a problem.

gundog
11-29-2010, 01:16 PM
That is a fact.

As far as the powerco is concerned, anything you have is inaccurate and probably dangerous. And you are a complete idiot whose every statement is stupid and can be ignored.

They have considerable evidence in favor of that opinion, so it is best to go along with it.

They DO usually believe that a 'civilian" can correctly identify blinking lights. Anything past that and whatever YOU say is ridiculous. Just go along with it, and have them check it if you think there is a problem.


What you say is true. I could not tell you how many so called electricians are out there, anyone with a wiggy is considered an electrician to the customers. I have followed up many so called electricians that claim the problem is on the PC side of the meter only to find a loose connection on a breaker or failed main breaker Etc. I am not saying all electricians are bad some are very good as a rule most engineers make lousy trouble shooters. Engineers tend to try and use code and the assumption the system is up to the latest codes and that is a huge mistake. Some electricians that are very good on new installs are not good at trouble shooting. Not all power company personnel are good at trouble shooting either and the more experience you have the more you know you might run into a new condition on any call.

We get a call every month or so of bad voltage only to show up and show the customer their HF volt meter is inaccurate.

Trouble shooting electrical problems is not cut and dry anyone who says it has to be a neutral from your description has not done much trouble shooting. The problem could be any number of things and without being there to check it out in person it is hard to tell. Example and this is one of a million power company has a primary voltage Cap on the line that has a time, current or voltage control and it is bad kicking the Cap on and off several times causing voltage fluctuations maybe that was damaged in the lightning storm. You could have a lightning arrestor arcing somewhere but has not taken the circuit out or maybe a tree limb contacting a line and operating a recloser. Are you starting to get what I am talking about? These problems are hard to diagnose. This is the reason for the recording volt meter so we can decide where the problem is on your equipment or ours. So say I set the RVM at your house I will ask you to record the time of day you see these fluctuations then when we download the information from the RVM we will compare to what you are seeing. If we show a problem that coincides to what you have recorded then we know it is our problem and we start the search on our side this can be very difficult at times.

If the problem is on the customer’s side we usually try and give a little help before leaving at least I always did. I would start by checking for loose connections at the meter panel or load center breakers that feel weak Etc. Many times problems come from unlicensed people wiring things and crossing a neutral with a hot leg etc. Another source of many problems is electric water heaters and the problem could even be at your neighbor’s house but shows up in your service. Are you seeing why I don't think giving advice on the net is a good idea? How many times do you hear the news and a house burns and they blame it on faulty wiring sometimes people die in these fires. I do not want to have a miss communication with someone who does not understand. I am not saying you guys fit that category but who knows who is going to read this.

Maybe one of your neighbors has installed a new heat pump and they are connected on your same transformer did they contact the PC to let them know they have added this additional load? The heat pump kicks on and voltage dips you see the fluctuation. Maybe you have a blacktop batch plant or some other huge power consumer on your circuit and their consumption is causing a problem on the circuit. I could write possibilities all day.

I do not give advice on the net about trouble shooting electrical problems because I never know what the experience is of the person reading said advice. Trouble shooting electrical systems is not easy. Throw out all the rules because you never know who worked on the system last (customers side) when engineers start spouting the NEC specs and applying these things to trouble shooting it only shows they have not trouble shot anything except on paper. I am not trying to say engineers do not know about electricity quit the contrary but trouble shooting is an art and no one has seen it all and nothing is a definite until you confirm with a repair. Occasionally things happen that no one can explain if have seen a couple of these in my 30 years in the business.

Mike

Evan
11-29-2010, 04:36 PM
Heh. Secret code at the power company here for "We have no effin idea what the problem is." = "Must have been a bird got fried on the power line."

gundog
11-29-2010, 07:55 PM
Heh. Secret code at the power company here for "We have no effin idea what the problem is." = "Must have been a bird got fried on the power line."

Sometimes we don't have any idea what is causing the problem. The newer relays in the sub help they can give you a distance to the fault if it is tripping the circuit causing a lot of momentary outages. The technology is getting better all the time but most of the circuits don't have this new equipment.

One thing that can give us problems that are hard to find are leaking insulators they are not quit bad enough to fail and cause a permanent fault and a large flash but they can occasionally relay the circuit. Trees & birds, squirrels, rats can also create a lot of problems companies trim trees on a circuit rotation every so many years but sometimes it is not soon enough. We also put guard on jumper wires for birds and animals when we have outages caused by them. The new stuff is all built with the guard in areas where we have bird /animal problems.

Donít forget the man made problems car hit pole accidents and people falling trees into the lines. The first good weather after Christmas we get several amateur tree fallers dropping trees through our lines. Then you have the people who dig through the lines. People cut the substation fences and steel copper and every so often they steal the wrong wire and justice is served on the spot.

The electric system is a fairly complex animal that changes constantly. No excuses just the facts and some companies spend more money than others. If you live in rural area it is expensive to maintain your system compared to revenue earned. The big cities are where the money is lots of customers and not near as many line miles to maintain.

Mike

J Tiers
11-30-2010, 12:33 AM
Gundog is correct that many many issues CAN cause voltage variations.....

As for suggesting neutral problems as a "marker" for bad troubleshooting skills, that's just , well, wrong..........

A "local" problem with blinky lights is commonly a neutral problem, I have seen several such just in the immediate area. Twice at our house, and others elsewhere.

The neutral is the wire that can be open or have a crummy connection and you still have power..... if one of your two hots opens or has a bad connection, you either lose some circuits, or you see a voltage drop while the bad connection gets hot. A bad connection in the drop neutral doesn't get as hot as fast, especially if you have a water pipe ground, because the circuit has other ways to "compensate and equalize". Even an open drop neutral does not have to mean anything past blinky lights, if your ground is via water pipes common to other houses. I have personal experience to verify that.

Naturally there is other equipment which can cause that sort of fault..... I remember once the voltage was stepping up and down over a 10V or so range, 2V or so per step..... Apparently an automatic tap changer had gone awry and was "hunting"....

But usually, that sort of trouble covers a much larger area, not just 3 or 4 houses..... 3 or 4 houses is exactly what a typical pole transformer serves in our area... And the powerco does not "waste" equipment providing automatic tap changers etc on individual pole transformers.

Evan
11-30-2010, 09:08 AM
...The technology is getting better all the time but most of the circuits don't have this new equipment.


We still have single phase circuits up to 100 miles long to serve very small towns around this area. We were on a single phase circuit out his way for a long time. It uses to trip off like turn signals. Then one year we had a spell of -30 to -49 weather for a couple of weeks. The lines almost melted off the poles. One of my friends at the power company told me that the lines were sagging over a foot between poles and that we came within a hair of having the power cut. They were sweating bullets on that one and the next spring they put three phase out this way.

Since the fires the power is really crappy. A long section of this circuit was in the fire zone. It's amazing how much difference dense smoke makes to the conductivity of the air and how much it pollutes the insulators and even the wires. I took pictures for the power company of the main transmission lines to Vancouver using my astrophoto techniques to produce the same results as a $100,000 UV corona camera. They were losing 20% of their power to corona losses for around two months this year.

This image was taken in near total darkness with a 1 minute exposure and an ultra sharp converted telephoto lens that I adapted to fit my Canon 350D. The tower is about 1/4 mile distant. The Company was concerned about the insulators breaking down, which they didn't.

http://ixian.ca/pics8/west_tower.jpg

gundog
11-30-2010, 10:25 PM
Gundog is correct that many many issues CAN cause voltage variations.....

As for suggesting neutral problems as a "marker" for bad troubleshooting skills, that's just , well, wrong..........

A "local" problem with blinky lights is commonly a neutral problem, I have seen several such just in the immediate area. Twice at our house, and others elsewhere.

The neutral is the wire that can be open or have a crummy connection and you still have power..... if one of your two hots opens or has a bad connection, you either lose some circuits, or you see a voltage drop while the bad connection gets hot. A bad connection in the drop neutral doesn't get as hot as fast, especially if you have a water pipe ground, because the circuit has other ways to "compensate and equalize". Even an open drop neutral does not have to mean anything past blinky lights, if your ground is via water pipes common to other houses. I have personal experience to verify that.

Naturally there is other equipment which can cause that sort of fault..... I remember once the voltage was stepping up and down over a 10V or so range, 2V or so per step..... Apparently an automatic tap changer had gone awry and was "hunting"....

But usually, that sort of trouble covers a much larger area, not just 3 or 4 houses..... 3 or 4 houses is exactly what a typical pole transformer serves in our area... And the powerco does not "waste" equipment providing automatic tap changers etc on individual pole transformers.

I have fixed many open neutrals. I should have been clearer I did not say it could not be an open neutral I said from his description and not being there that would not be a proper diagnoses to just assume that was the problem. Flickering lights are usually caused by a bad hot leg connector. Bright and dim is usually an open neutral. For every rule there is an exception that is why I said you may see just about anything when it comes to electricity that is why it is called a theory. When something happens we can't explain on the line crews we call it FM that stands for F*** Magic.

Typical open neutrals give high voltage on one leg and low voltage on the other the reason for this is the current is back feeding through a 220v appliance and rather than returning on the neutral the current is returning on the other hot leg thus making voltage on that leg very high. Surge protectors will and do catch fire when the neutral is open. Open neutrals can be very dangerous.

Mike

J Tiers
11-30-2010, 10:49 PM
Yep, I know you "get it", no fear there......

Since the OP described "surges" as well as flickering lights:


I feel lucky that I was in the bathroom where I saw the light bulbs get very bright all the sudden

The idea of neutral problems appeared to be reasonable, perhaps at the pole transformer if the neighbors were seeing it too.

naturally it could be other things. Your suggestion that a compensation cap could indeed be cutting in at bad times, which should raise the voltage, etc, etc.......powerco equipment has lots of ways to have problems.

gundog
11-30-2010, 10:57 PM
We still have single phase circuits up to 100 miles long to serve very small towns around this area. We were on a single phase circuit out his way for a long time. It uses to trip off like turn signals. Then one year we had a spell of -30 to -49 weather for a couple of weeks. The lines almost melted off the poles. One of my friends at the power company told me that the lines were sagging over a foot between poles and that we came within a hair of having the power cut. They were sweating bullets on that one and the next spring they put three phase out this way.

Since the fires the power is really crappy. A long section of this circuit was in the fire zone. It's amazing how much difference dense smoke makes to the conductivity of the air and how much it pollutes the insulators and even the wires. I took pictures for the power company of the main transmission lines to Vancouver using my astrophoto techniques to produce the same results as a $100,000 UV corona camera. They were losing 20% of their power to corona losses for around two months this year.

This image was taken in near total darkness with a 1 minute exposure and an ultra sharp converted telephoto lens that I adapted to fit my Canon 350D. The tower is about 1/4 mile distant. The Company was concerned about the insulators breaking down, which they didn't.

http://ixian.ca/pics8/west_tower.jpg


That looks like a 230KV line by how many insulators are in each string. On extra long Transmission lines they usually put in Tramp (tramposition) towers they roll the phases to a different possition basically just rolling the phases you will see tramp towers every so often the jumpers and insulators look kinda crazy and you probably think what does that look like that for? They roll the phases to try and break up the corona. they have now found they have less corona formed when the align the phases in a delta (triangle) equally spaced. The tower you show has all the phases on the same plane and that is how they used to build most tower lines either in a horizontal plane or a vertical plane. the theory on the delta construction is that each phase cancels the other out when spaced 120* apart just like they draw the vectors of a delta connection.

Here is an example of a double circuit tramp tower.

http://img.photobucket.com/albums/v292/millnut/tramptower.jpg

The carbon in the smoke can cause high voltage lines to cross phase and the carbon in the smoke contaminates the insulators the blacker the smoke the more carbon present.

I worked one outage where a farmer was burning the trees from an orchard they had just removed under a 69KV line and it flashed over and burn't the line down. When the line fell it hit a storm drain, the storm drain was burried next to a 6" high pressure gas line it arced over to the gas line and when we got there, there was a flame shooting 60 feet in the air. they told us as long as it was burning it was safe when they put it out is when it was the most dangerous because a spark could cause an explosion. They watered down the eart around where the gas was blowing to help reduce the chance of a spark. It was interesting watching them repair the line.

Mike

Evan
12-01-2010, 02:14 AM
That is actually a 500kv circuit. It is one of three that run parallel from the Bennett dam in northern BC. That is the oldest of the lines and all the towers are the same. That line is also very close vertically to a well used road that passes under it on the side hill as the line climbs up the ridge. It is just 3 kilometres from here and when I drove out there to take the pictures I stopped under the old line. When I got out of the truck I could feel what is left of my hair standing on end. That is NOT a good thing to feel so I got out of there. With all the ionized smoke particles the field may have been getting close to flash over.

I spoke to the managing engineer of BC Hydro Transmission Systems and they sent a crew out the next morning to make some measurments. The other two circuits are on much taller towers.

Arcane
12-01-2010, 09:23 AM
I always thought transposition structures on transmission lines were used to keep the voltage equalized between all three phases. It's been over 30 years since I worked Transmission, and I've forgotten the exact reasons behind it. Delta construction was supposed to have more capacitance between the phases closer to earth, so doing a transposition would remedy that. I've never heard of that being used for corona control, I always thought that was more of a problem with sharp corners on hardware and too small of wire diameter for the voltage and that sort of thing. We used to have a lot of 25Kv Delta construction on the old 3 phase lines here. Since all the tap-offs were from the bottom two phases, they had to use transposition structures just to be able to balance the load. I don't think there are any of those lines left, all rebuilt with flat construction now. Nasty things those Delta lines were too, steel tri-arm and double skirted insulators. I remember changing out miles of those things and installing wood crossarms to gain a bit of ground clearance because of the higher equipment farmers were using. We used 36Kv Class 4 rubber gloves out of an insulated bucket on an insulated boom bucket truck and did it all by hand, no sticks. After awhile we got fast, we could do a structure every 12 minutes when conditions were good...lazy government workers that we were.

Evan
12-01-2010, 10:31 AM
I don't think they bother with any special hardware here to transpose the phases. BC is nearly all mountains and hills. When the line has to cross a valley or gorge they cross the lines over by hanging one line lower than the other two.

The interesting thing about the line in that picture is that it shouldn't be showing so much corona discharge. It is the oldest line and the sharp nicks and scrapes should be weathered down more than the newer lines. The newer lines had much less corona which is reverse of usual. A lot has to do with altitude too. The lines in that picture are at about 2400 feet. As altitude increases so does corona loss and it goes up exponentially. Lines running at altitudes above 3000 to 4000 feet lose the most power to corona, not resistance or other effects. It changes with the barometric pressure too.

J Tiers
12-02-2010, 12:12 AM
I always thought transposition structures on transmission lines were used to keep the voltage equalized between all three phases.

Transposition will tend to do several things....

Reduces line inductance, by "interweaving" the individual lines and avoiding long lengths of the exact same relative orientation

Balances capacitances by moving the lines around so that they are each "on top", "in middle", or "at bottom" part of the time.

It is a sort of very large geometry "litz wire", although the analogy is not very exact.

I doubt it would have anything significant to do with corona, that has more to do with voltage, "sharpness", and weather conditions, etc. Moving wires around might possibly affect the electric field (in volts per meter), but I can't immediately see how it would be anything other than a relatively minor effect on corona.