MAD for residential service drops

Bart_ said:
Power distribution has another neat feature, inductance of the line. In brief, when you try to interrupt the current, the inductance kicks up the voltage to try to maintain the current flow. That's why substation interrupters are so fang dangled - dealing with the inductive arc. Inductance is your friend when you want an arc, like a welder. Welding and water - boogeyman!! (generally avoid) Unless you're welding a gas tank. Then there's power factor correction so less I is required to get PWR = VxI because there's actually a phase angle between the current and voltage and in phase is useful real power, out of phase just warms up your lines and enriches the power utility.

eyes glazing over yet

Do you figure the house drop transformer contributes significant inductance?

On the welding boogeyman, its 10's of volts but usually the 60 Hz or 120 Hz rectified so some heart and muscle concern is warranted. But the item is grounded so your sweaty welding glove is ok:)


In a storm cleanup situation All bets ought to be off as line crossing can occur somewhere you don't know. But if Wilber's tv and clock radio are fine and it isn't storm cleanup you can ratchet down your tenseness level.

For cheap arborists could be equipped with non contact line voltage sensors. Stick it on a pole, see how hot the line is - unless it's obviously sizzling and snapping. Live or unenergized for a start (?) Is there already such a lineman tool? I've got an indoor very close sensing tool but it's for bench top use.



Oh, and on inadvertently cutting the house drop line - it won't be a nice non-event like mowing your electric mower cord. Everything downstream of the panel is breaker and also sometimes GFCI protected so when a short fault occurs (overcurrent) it gets shut off (open circuited) presto. But the line coming from the pole has a lot more gumption and could deliver hundreds of amps into even just 120V to neutral and is intended to NOT shut off to my knowledge under heavy current - now that's about 5x normal weld arc and a dang high current knob setting (industrial!) so its gonna be a nasty big arc. So, faux pas!!!!!!!
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You are pissing on my parade. :)
Yep, gonna blow a chunk out of your nice new Sugihara bar and chain, and probably spatter molten metal about as it makes a loud boom and temporarily blinds you with an arc. Bet you will watch where you're cutting around service drops from then on.
Just don't think that if you get within the MAD 10 foot range that an arc is going to jump from the line and get you. You reach up under the lamp shade on the nightstand and turn off the light before you go to sleep. Your fingers are on a metal light socket within 3/8th of an inch of a 120 volts that is insulated from that metal your hand is on with a piece of thin cardboard.
 
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Well worded.. I've seen one tree way too up and close hit a house drop. It yonked the weather head anchors and folded it in half, it had me thinking a breakaway might be a good idea on those pesky things. We could hear an arc running up and down the old metal weather head, and I have no clue on why it never blew the transformer.
Its all knowing what you can and what you can't get away with, and when to call in for a disconnect. Personally I think it's akin to one handing a chainsaw or speeding, something to be avoided but hyper vigilant when its done and compliancy should be avoided.
Should they teach how to speed safer? Perhaps! I've avoided a head on when my wife was 8 weeks by dropping a gear and punching it. If I panicked and hit the breaks we would have been toast! Honestly I didn't get those skills from always obeying the rules in my youth. Same with one handing a saw, saved myself when I was pinned by a top.
Like one handing, it's going to be done and that horse has been beaten to death but still comes up because people do it all the time.
 
So, what about the inductance and non contact "how hot" sensor? Seems you could sensor test a suspect tree too before ascent if it worked.

Looked up lineman tools and they seem to be contact type, unless I missed something.


Ren and Stimpy "Don't wiz on, the electric fence":)
 
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Bart_ said:
So, what about the inductance and non contact "how hot" sensor? Seems you could sensor test a suspect tree too before ascent if it worked.

Looked up lineman tools and they seem to be contact type, unless I missed something.


Ren and Stimpy "Don't wiz on, the electric fence":)
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Mine is a Klein 80V-230KV non contact meter. AEMC is a popular one with the fellows I work with but they are 240V-275KV. Mountable on hot sticks, or hand held for the lower voltages. I believe mine ran around 350 dollars when I bought it, but that was a few years ago.

Probably wouldn't fly these days, but I went to school grades 1-8 in a small school in farm country. The school property was bordered by a road on one side and farm fields on three, so three sides were an electric fence. That fence was the big source of entertainment during recess. Games were played using it, and the teachers would join in. Get 25 kids holding hands and the one on the end would grab the fence. Or, jump up in the air and grab the fence and try and let go before your feet touched down. It was our high jump wire as well. No baseball, football, basketball, just an electric fence to play with. That or mumbly peg. Yeah, all the boys had pocketknives in school, and if you hunted on the way to school, or on the way home you had a gun as well that went into the closet during the day. Nobody ever got shot or stabbed. If things got way out of hand you got into a fist fight. The idea of pulling out a knife or grabbing a gun never entered your head. Life was good back then.
 
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Wow, $738. Sounds a bit high, but I have not bought one in several years. Maybe because it also does 15 & 25KV underground. Hastings make good, light weight hot sticks, if you like fiberglass ones.

PS: Yep, pretty much $550.-$750. About doubled in the last 7 or 8 years. In line with everything else, I guess. Anything that mounts on a hot stick cost ten times what it should.
 
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What is the proximity required to get a reading? On the many kV lines arcing is an issue hence the hot stick with all its attendant care, but what about for the lowly 120/208/240 genre? And has anyone ever "sensored" an object like a car chassis or tree?

ps read the 7701 manual and it doesn't say how close it has to be to successfully read voltage(?)
ps read the klein manual and it states "Always maintain the minimum approach distances listed in OSHA Tables R-6 and R-7 on pages 8 & 9 in this manual." For lower voltages its a few feet. Does that match up with your usage experience?


pps what about this gizmo - finds 220v @15 feet

Hotstick USA AC Hotstick Voltage Detector for Firefighters, EMT and Police Safety​


"Detection Distance: (at High Sensitivity Level) at a Frequency Range of 20Hz to 100Hz. 120-220VAC : 15 feet (3 feet if on wet soil) 7.2-16kV : 210 feet (overhead distribution line) 46kV : 500 feet (overhead transmission line) Additional Sensitivity Levels Include Low Sensitivity and Focused Setting. (With Self-Testing function) Signal indication includes audible beep and visual LED."
 
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Bart_ said:
What is the proximity required to get a reading? On the many kV lines arcing is an issue hence the hot stick with all its attendant care, but what about for the lowly 120/208/240 genre? And has anyone ever "sensored" an object like a car chassis or tree?

ps read the 7701 manual and it doesn't say how close it has to be to successfully read voltage(?)
ps read the klein manual and it states "Always maintain the minimum approach distances listed in OSHA Tables R-6 and R-7 on pages 8 & 9 in this manual." For lower voltages its a few feet. Does that match up with your usage experience?


pps what about this gizmo - finds 220v @15 feet

Hotstick USA AC Hotstick Voltage Detector for Firefighters, EMT and Police Safety​


"Detection Distance: (at High Sensitivity Level) at a Frequency Range of 20Hz to 100Hz. 120-220VAC : 15 feet (3 feet if on wet soil) 7.2-16kV : 210 feet (overhead distribution line) 46kV : 500 feet (overhead transmission line) Additional Sensitivity Levels Include Low Sensitivity and Focused Setting. (With Self-Testing function) Signal indication includes audible beep and visual LED."
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I can only speak for the Klien that I use, but they all seem to be pretty much the same. It doesn't give me a reading perse' but an indication of voltage. You pick the range you are looking for. It will beep at you and light up if there is that voltage present in the line. Distance is determined by voltage to some degree, but if the line is hot it will let me know within about 3-4 feet of the cable on a 7500, about 8 feet on a 20KV line (mine). You can crank up the sensitivity but you get some funky things happen when you do that. Good for buried lines though.
I have used it to find underground 120 volt lines for friends that wanted to dig up parts of their yard for projects. Not as nice as one built for that purpose, and a little more general direction than those, but it does work. My current tracer is better suited for that.
I regularly checked trees because I climb them when they are on power lines during storms when it is raining, or just after a rain. I have never found an indication of voltage on any tree that was on a powerline. None. Not at base level. Don't check higher because it would be a waste of time and effort. All I care about is, can I get in the tree with both my feet off the ground without getting fried. If I can, and I always seem to be able to, I am good to go.
The MAD distance for line workers varies with voltages and is silly to some extent as it conflicts with some work that needs to be done on occasion. But rather than try and remember what distance for what voltage I make a conscience effort to try and maintain the distance for the highest voltages I work on, which is 69KV, and I keep about 15 feet separation. If I recall correctly, it actually is 13 feet for that voltage, but that in itself is silly because who can judge that close, and you certainly are not going to whip out your tape measure and have at it. "Hey new guy. Take the end of this tape measure and hold it against that powerline over there for me."
120 volt/240 volt house drops I pay no attention to MAD as long as the lines are up and working as they should be. If I am working in a tree and they are in my way I will hold them out of the way with my hand or hip.

That

Hotstick USA AC Hotstick Voltage Detector for Firefighters, EMT and Police Safety​

looks like it might be something good for firemen and such, but it doesn't tell you much about voltage, just that there is some there, somewhere. Not something I would have an interest in.
 
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My experience is much the same with the hastings. You set a voltage range and work your way up or down. For 120-240 the unit is all but touching the wire. The higher voltage the further away it detects it.

I have picked up voltage on fences, downed comm lines, and the like. Never on a tree, but I like to check especially if they are wet.

It is a valuable tool for the cost of a big saw. Not saying every crew should have one(yet). But if you do a lot of storm recovery with downed lines and the associated wreckage it would be a fine investment.

my .02

Tony
 
What would be an appropriate electrically insulated glove that would allow one to handle a service drop? I get that if it’s in good shape and not worn/damaged that you could move it bare handed. I usually use a dry stick or a fiberglass pole just because I’m afraid. I won’t work on trees that have anything more than a service drop running through them. Electricity scares me more than heights and rotten trees.
 
Treeaddict said:
What would be an appropriate electrically insulated glove that would allow one to handle a service drop? I get that if it’s in good shape and not worn/damaged that you could move it bare handed. I usually use a dry stick or a fiberglass pole just because I’m afraid. I won’t work on trees that have anything more than a service drop running through them. Electricity scares me more than heights and rotten trees.
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It doesn't take expensive gloves to insulate you from service drop voltages. I see electricians that use those 2 dollar dish washing gloves. But if you want something that is officially rated you can buy them for about under 15 dollars
which are good to 20,000 volts. Your house drop is at most 240 volts, so you are way over protected. Then you can go to a brand name glove and spend upwards of 300 dollars for them, but they really don't do anything more other than being a bit more flexible and usually come with a leather glove that goes over the top to protect them being damaged or poked through by a broken wire end. The expensive ones don't seem to last as long as the cheap ones, probably because they are made to be more flexible. Good idea to wear a larger glove over them to protect the rubber.
Any of the rubber insulating gloves should be inspected before use to see if the rubber is getting old and cracking. If so, throw them away and get a new pair. I usually just buy new insulated gloves every year, and I get the name brand ones that come with leather protectors and a canvas bag to store them in because I like the flexibility of them, not because the protect me any more than the 15 dollar ones. It is a high price to pay for a bit more flexibility, but hey.
 
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Errrr right, I feel I'd be remiss here not to weigh with a thought about fake parts (it's even happening in the jet engine maintenance business and cranes/ heavy lift which I've talked about elsewhere on TreeBuzz) and cheap Chinese knockoffs for all sorts of other stuff. Industrially, we have had BIG problems with chemical protective gloves and suits we later found were sourced back in China. These had fake branding and packaging but turned out to be as porous as cotton gloves basically . . . nitrile, etc. in a pigs eye . . . not what you want with chemicals that carry the SKIN notation (i.e. can penetrate intact skin). Looking at prices for some made in N America or U.K. Class 2 electrical gloves, dunno . . . . can always put 'em inside leather gloves I guess . . . . but no warm fuzzy at all from me. Just sayin'. My 2 cents.
 
ghostice said:
Errrr right, I feel I'd be remiss here not to weigh with a thought about fake parts (it's even happening in the jet engine maintenance business and cranes/ heavy lift which I've talked about elsewhere on TreeBuzz) and cheap Chinese knockoffs for all sorts of other stuff. Industrially, we have had BIG problems with chemical protective gloves and suits we later found were sourced back in China. These had fake branding and packaging but turned out to be as porous as cotton gloves basically . . . nitrile, etc. in a pigs eye . . . not what you want with chemicals that carry the SKIN notation (i.e. can penetrate intact skin). Looking at prices for some made in N America or U.K. Class 2 electrical gloves, dunno . . . . can always put 'em inside leather gloves I guess . . . . but no warm fuzzy at all from me. Just sayin'. My 2 cents.
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I agree with you on most things, but it doesn't take a hell of a lot to insulate you from 120/240 volts. Your extension cords, and lamp cords are cheap Chinese plastic, and you grab that. Like I said, even dish washing gloves work but the cheap 15 dollars ones are much better, Chinese or not. I have used both and can't tell the difference except the expensive ones are more flexible and usually come with leather protectors and a carrying bag, all of which you are paying more than double for. The rubber expensive one rot fairly quickly. By that I mean in a couple of years they are shot. The cheaper, less flexible ones last twice as long. That said, I buy the expensive ones for the flexibility, the protectors (which I wear out) and the canvas bag so I know where my gloves are. Unless you work with power lines a lot, you don't need that crap. If I were only going to be working with service drops a couple times a year, I would probably get the cheapest rubber gloves I could find, rated or not, if I got anything at all.
 
I agree that most of the Chinese knock offs aren’t up to par with their applications. But, yeah, after the explanation, as long as it’s a piece of thick rubber then it will be fine. Kinda hard to mess that up. It’s just for a very small fraction of their “rating” anyway. I certainly wouldn’t trust Chinese gear on higher voltage.
 
Another way to look at this is with electrical tape. One turn of most major brands (as in: 3M-Scotch) of electrical tape is rated for 700 or higher volts. Think how thin that piece of electrical tape is... 700+ volts. Service drops are 120/240 volts.
Practices say we wrap certain numbers of turns on bare electrical wires for different voltages, but one wrap is all that is needed to insulate you from anything you will be in contact with. The reason you put ten wraps on a 480 volt motor connection is not for insulation value but because vibration over time wears through the tape layers. We also put a few wraps of varnished cambric on before the tape goes on to help prevent sharp corners from wiring connectors from poking through the tape. But in a perfect world, one layer of tape would do.

Once again, we are taught, or scared into thinking a service drop is some high-powered force that will zap us dead if we get too close. If it is in good shape it is no more dangerous than your lamp cord. If it is old and weather checked, or damaged, treat it as such with the knowledge you can get shocked severely. If you drop a small limb on it, it is not going to go boom and create a fireball. If it is in good shape it is not going to do anything.
Don't cut it with your saw and try not to spur it with your gaffs. And there is no need to manhandle it if you don't have to, because if it is old it may crack up the insulation as it gets brittle over time. Treat an old service drop as you would an old brittle lamp cord. Both can kill you if you allow them to but nothing is going to jump off of it and get you while you are working in a tree.
Under ideal conditions (atmospheric pressure; temperature; humidity; good solid ground, with sharp points on the hot and the ground) the furthest 120 volts can arc is 1.5 inches. A bare wire service drop could not arc more than 1/2 inch to a solid ground. You are not a solid ground by a long, long shot and I doubt you could get an arc to you at all. To be zapped you would pretty much have to be touching the bare conductor, or at least have some moisture, or other conductive material between you and the bare conductor.

I reiterate, we need to train people, not frighten them about realistic electrical things they will be dealing with. A person who is scared to be working around a service drop is more likely to get hurt.
 
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Those with the gear could do a PSA experiment next time you encounter a sizzling primary to tree situation (likely dew or rain induced, like the one I saw) and try to measure the tree. Proof of concept.

data sheet https://www.frsa.com.au/FRSA/media/...3-10-0200-hotstick-datasheet1_AC-Hotstick.pdf

gives away clues to some physics and antenna theory that makes these gizmos work. Voltage range on the $$ units is just amplifier gain and the option of omni antenna vs directional is good to have. Acknowledgement of shielding etc affecting operation kind of confirms the inner workings.


If you want to mess with the innocent, tell them to hold the motor down by sitting on top of the cylinder while you yank the pull starter. kids can be cruel. but learn quickly Bravery - hold the plug steadfastly against the engine housing while checking for spark. don't slip! ;)
 
Bart_ said:
Those with the gear could do a PSA experiment next time you encounter a sizzling primary to tree situation (likely dew or rain induced, like the one I saw) and try to measure the tree. Proof of concept.

data sheet https://www.frsa.com.au/FRSA/media/...3-10-0200-hotstick-datasheet1_AC-Hotstick.pdf

gives away clues to some physics and antenna theory that makes these gizmos work. Voltage range on the $$ units is just amplifier gain and the option of omni antenna vs directional is good to have. Acknowledgement of shielding etc affecting operation kind of confirms the inner workings.


If you want to mess with the innocent, tell them to hold the motor down by sitting on top of the cylinder while you yank the pull starter. kids can be cruel. but learn quickly Bravery - hold the plug steadfastly against the engine housing while checking for spark. don't slip! ;)
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Damn thing is only good down to -22 degrees. Useless here during the winter. LOL
Sounds like a good contraption for some people. I can see where it might give you false readings if you are checking a service drop and there are primary lines nearby, given the range it picks up.

In high school I was known for putting a plastic spider in the urinals. Attached to the spider was a very thin wire which ran over to a stall where I was with my aircraft engine magneto that put out about 20,000 volts. You know the guy is going to try to wash the spider down. A spin on the magneto usually got an appropriate response. Yeah, I got wailed on a few times, but it was worth it.
 
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So this discussion maybe begs one more question - whats the amount of juice going to streetlights? Still 120 V? I’ve hung a branch on one of the lines going to a street lamp years ago and some of em seem to have pretty thick copper coming up from the buried portion. Cheers
 
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