MAD for residential service drops

To be sure, you have to know your local utility's system. Mine uses 4800 V, 8300 V, and 13.8 kV for distribution; and 24, 40, 120, 138, and 230 kV for subtransmission. Other utilities use other voltages, but some of these are common. Some of the lower subtransmission lines share pole space with distribution lines through residential areas, like in the photo. If a pole has what looks like more than one set of primaries, and the top set is of a "beefier" construction, it could be a subtransmission line, and probably at a higher voltage.
 
Powerlines Semi Advanced Class
Why the high voltages?
Power plants may create power with only 2KV. Then they have to send that somewhere over long distances. A fellow by the name of Joules figured out that the higher the current the more loss there is in transmitting it by a factor of 4. So if you reduce the current by half you reduce the loss by 4 times. Woooho! But now you have less current. Solution, bump up the voltage.
Remember the water pipe? Water = current. pressure = voltage. So the power companies bump up the voltage to triple K figures to transmit the electricity over long distances. When it gets near you it goes to a substation that knocks the voltage down and the current back up. These lines are what we call sub-transmission lines and are usually 26-69KV. As they get close to your home they are knocked down to 4-13KV and are called primary lines. Those go to the round bucket transformers you see on the pole in your neighborhood where they are reduced once again to 120 volt lines, two different phases that go to your house and are called service drops. They are the ones they put the insulation on because they usually wrap them into a bundle, and they don't want homeowners poking them with metal handled stuff. Although, there are some placed that string three separate lines to your house, but those are about gone these days.
And then, to top it off, nothing actually goes from the power generating plant to your house. An easy way to think about what happens is to think of a bunch of cars in a drive in theater all parked next to each other. Each car is only allowed to have one person in it. But a guy (the power company adds one electron) climbs in the first car that has someone in it already. That guy that was in there has to get out and get in the car next to him, which drives that guy out and into the next car, and so on down the line. When the fellow in the last car is driven out, he ends up powering your stereo. The guy who got into the first car is still back there in the first car, and he is going to get back out in a fraction of a second. The only thing that moved was one electron from its spot next door. Nothing came from that power plant to you. And because it is alternating current, the fellow gets back in the car he was kicked out of at your end and the other fellow gets back into the car he had come from and it continues until the current reverses again. In our case it flips back and forth 60 times a second. So you see that nothing actually travels in a powerline in reality, just electrons jiggling back and forth.
 
Last edited:
Don't forget mini lecture 120Vac RMS is actually a 170 volt peak sine wave. 240Vac is 340 Vpeak. 600Vac is 850 Vpeak yikes. Also skin impedance is pretty good (insulative) at 50 or 60 Hz vs medical equipment which transmits current through the skin just dandy in the kHz. So don't chest short your HF start tig. Keep one hand in your pocket chest path safety rule when helpful.

You're a treasure of knowledge. :)
 
Bart_ said:
Don't forget mini lecture 120Vac RMS is actually a 170 volt peak sine wave. 240Vac is 340 Vpeak. 600Vac is 850 Vpeak yikes. Also skin impedance is pretty good (insulative) at 50 or 60 Hz vs medical equipment which transmits current through the skin just dandy in the kHz. So don't chest short your HF start tig. Keep one hand in your pocket chest path safety rule when helpful.

You're a treasure of knowledge. :)
Click to expand...
Hey, someone else who must have a bit of an electrical theory background! Electricity is amazing, isn’t it?
 
Check this out:

Hunter S Thompson on: Electricity

Lock one hand behind your back before you touch anything full of dissatisfied voltage-even a failed light bulb-because you will almost certainly die soon if you don’t. Electricity is neutral. It doesn’t want to kill you, but it will if you give it a chance. Electricity wants to go home, and to...
www.treebuzz.com
 
I just wiped off a long article I wrote about RMS for those who might be wondering what that was. When I got done with it, I thought, what does a bunch of tree people care what ROOT MEAN SQUARE is. So, it's gone, and I am not going to rewrite it.
My fault, I got sidetracked on this service drop thread and started yammering about a passion of mine. I think people's questions have been answered about MAD and service drops. If not, please keep asking. RMS is something you really don't need to clog up your brain with, and it is not important to anyone except us electrical nerds. And it just adds a couple of hundred dollars to the cost of our multimeters. Thank you Fluke!
 
Tom Dunlap said:
Check this out:

Hunter S Thompson on: Electricity

Lock one hand behind your back before you touch anything full of dissatisfied voltage-even a failed light bulb-because you will almost certainly die soon if you don’t. Electricity is neutral. It doesn’t want to kill you, but it will if you give it a chance. Electricity wants to go home, and to...
www.treebuzz.com
Click to expand...
Something to be said for that. Electricity comes in on a hot and wants to go home, and it normally does that by the neutral, which is the easiest path home. A fault that does not allow it to go home on the neutral will cause it to seek another route home. If all was done properly that will be a ground, which will eventually bring it back to a viable neutral.
Neutrals and grounds are not the same thing. You don't wire a light bulb with a hot and a ground. It will light, but you have then energized your ground. A lot of plumbers have been fried because of bad wiring choices like that. Grounds are there for the sole purpose of protecting people from being zapped if there is a fault in the path home for electricity. Without the ground it will look for another route home, and that then might be you. You don't want it traveling through certain parts of your body. Head and chest. That is the killer parts. If its path does not go through either of those, and, the voltage is that most of us will encounter, you will probably survive just fine. Keep one hand in your pocket or tucked behind your back so if you do touch something hot it won't flow through your chest to the other hand that is touching something that will take it home. With your other hand in your pocket the best path for it to take then is down your legs and through your shoes with a somewhat rubber type sole and a floor that usually is not very conductive. All in all you are pretty well insulated, and with household current you will get that startling buzz that makes you go, Ahhhh! And then you shake your arm and walk around the room say something about your mother's sex life.
 
I was dismantling a motor control center at a defunct sawmill. It operated on 480 volts 3 phase. I pulled out a bucket on its track, which disconnects the clips on the back from the buss bars. Stuck my hand in and got a dandy shock. Turned out the clips on the back of the bucket had broken and some idiot had wired the starter leads directly to the buss bars by drilling holes in the bars and bolting the leads to them.
I also found fuse boxes with steel bars in them in place of fuses, and contactors held down with small wedges of wood.
It was no wonder the mill had gone out of business. I assume it was managed with the same mind set.
 
Way, way back when I was a poor student, I moved into a new unfurnished apartment and bought the refrigerator from the previous tenant for a ridiculous low price I can't remember. It was probably $5, but, even so, I got ripped off. The refrigerator worked fine, but the door was electrically live. I just draped a dish towel over the door handle and opened the door with that. If I forgot, I would get a little buzz that was strong enough to get my attention but not so strong as to be a problem. But one day, in my rush to do two things at once in my small, galley kitchen, with one hand, I closed the door behind me without using the dish towel just as I was reaching with the other hand to turn on the water at the sink. This was not a small buzz. It wasn't even a big buzz. It was more like getting hit by a bus. I reflexively yelled, jerked my hands away, and even jumped up into the air. It changed me. I could not close my eyes for a few weeks without seeing the image of my hand reaching for the faucet. It was as if that image had been physically burned into my brain at that instant. I can still see it 40-plus years later. That same day, I cancelled my plans and bought a new refrigerator. I had to take out a loan to do it, but I was not going to risk that trauma again. My already healthy respect for electricity expanded to a new level that day.
 
@Shadowscape I don't pretend to have the knowledge you have but what I can tell you about is my 30 year history as a Paramedic and 25 years as a firefighter. I can tell you stories about the cardiac arrests and near electrocutions from 110. I can also discuss the requirements for wooden ladders to be nonconductive. When I first came in the FD wooden ladders were still a thing and the maintenance to keep them compliant was brutal for the rookie. Again I don't wanna try to say I know better but I have seen things that led me to respect electricity in any form a little more. I personally wouldn't recommend or actually jamb anything into an outlet under any circumstances. It's just not a prudent gamble. I also would not bet my life on the house drop covering. The linemen ground the truck and wear insulated gloves to handle them. Probably a good practice and done for a reason. Just my opinion that things that can probably kill you will eventually have the rite circumstances to do so. Not my mission to accelerate the process. The space I personally choose to operate in is to not deal with things I'm not an expert in and not take chances I can't justify. Its worked out pretty well for the last 50 plus years. I almost walked off a job site the other week because they wanted to lift a house feed to get the crane under with a pole saw extension with aluminum caps. Every time they lifted the wire it arched in the tree it went through. I impolitely told them if anyone does it again I'm leaving and they can kill themselves after I leave. No desire to do CPR on anyone again. I've done that thousands of times and I retired for a reason. I hear what you guys are saying but from a general approach, is it better to have these rules out there for the entire industry or to take for granted people will use the discernment those of you who are trained would use in a similar situation? I'd propose removing the option to handle the line would cause the greatest good for the most people. I'm also biased based on previous work history and the fact freak accidents and circumstances, as well as bad decisions by the genpop were my job security.
 
Last edited:
Shadowscape said:
You are correct. The insulation of service lines weather checks. Grab onto one that is 30 years old on a rainy day and you will understand that. But it all comes down to how well you are insulated as well. If you are up in a tree on a clear, dry day, the chances of you feeling anything at all are slim to none. 120 volts just doesn't have the force to go through you, your gear and clothing, boots, and a tree to ground. In terms of potential, 120 volts is pretty weak. Most of us have all been zapped at one time or another from something in our house. Makes your arm buzz and you say, Wow! Didn't kill you because you were insulated to a degree by your shoes, and the wooden floor you were standing on. Had you been standing bare foot on a metal beam you could easily have been killed. And what part of you it is going through makes a world of difference. Touch a hot line with one finger and a ground or neutral with another finger of the same hand and you will get a burnt fingers and hand because the current goes through your hand. Touch a hot with a finger on one hand and a neutral with the finger on the other hand and the current goes through your chest. Dead.
The service drop is no more or less dangerous than what is in your house, and has no more potential than what is at your outlets in your house. What it doesn't have is current breakers of 15 or 20 amps, but that doesn't make much difference because a half amp will kill you just as dead as 200.
If you need to work around a service drop with a ladder, use a wooden ladder. Insulated bucket truck. Or be up in a tree on a dry day. You can drop small branches on a service drop and nothing will happen, bare spots or not. They are not going to arc and flash and cause a fire. 120 volts just doesn't have that in it.
Think of an outlet in your house. I wouldn't hesitate to put the blade of a screwdriver with a plastic handle, or wooden handle on a hot screw of an outlet. That plastic handle or wooden handle is insulation enough to keep me from getting zapped. Same rules apply to service drops. Doesn't take much insulation to be safe from them.
We tend to get nervous around overhead wires because we have seen videos and pictures of tree workers having dropped a limb on a 20KV line and the fire and arcing that takes place. And pictures of fried people who have climbed up line towers and pole to steal copper where they are cooked like charcoal. Service lines to homes are not that. Respect them, for they can kill you if you do everything wrong. Knowlege is the best solution, not fear.
Don't give it a path to ground through you. That one rule alone will keep everybody safe.
Click to expand...
The effect on the cardiac muscle/heart also depends on where the cells are in the depolarization/repolarization cycle. You can be in a spot electrically that allows a critical heart rhythm to occur based on when the electricity is introduced to the heart muscle. This is done sometimes with the defibrillator. Synchronized vs unsynchronized cardioversion. The treatment changes based on the best time to depolarize the electrical component in the cardiac cells. If you get hit with 110 at the rite time in that cycle you will go into Ventricular Fibrillation and if not corrected nearly immediately will lead to death and or other bad stuff. The Joules for the cardioversion start fairly low. Is there a way to determine joules in a house feed? Is it even a relatable measurement? For instance you can cardiovert at 50 joules. How many joules would contact with 110 create? Truly never thought about it in this context.
 
Steve Connally said:
@Shadowscape I don't pretend to have the knowledge you have but what I can tell you about is my 30 year history as a Paramedic and 25 years as a firefighter. I can tell you stories about the cardiac arrests and near electrocutions from 110. I can also discuss the requirements for wooden ladders to be nonconductive. When I first came in the FD wooden ladders were still a thing and the maintenance to keep them compliant was brutal for the rookie. Again I don't wanna try to say I know better but I have seen things that led me to respect electricity in any form a little more. I personally wouldn't recommend or actually jamb anything into an outlet under any circumstances. It's just not a prudent gamble. I also would not bet my life on the house drop covering. The linemen ground the truck and wear insulated gloves to handle them. Probably a good practice and done for a reason. Just my opinion that things that can probably kill you will eventually have the rite circumstances to do so. Not my mission to accelerate the process. The space I personally choose to operate in is to not deal with things I'm not an expert in and not take chances I can't justify. Its worked out pretty well for the last 50 plus years. I almost walked off a job site the other week because they wanted to lift a house feed to get the crane under with a pole saw extension with aluminum caps. Every time they lifted the wire it arched in the tree it went through. I impolitely told them if anyone does it again I'm leaving and they can kill themselves after I leave. No desire to do CPR on anyone again. I've done that thousands of times and I retired for a reason. I hear what you guys are saying but from a general approach, is it better to have these rules out there for the entire industry or to take for granted people will use the discernment those of you who are trained would use in a similar situation? I'd propose removing the option to handle the line would cause the greatest good for the most people. I'm also biased based on previous work history and the fact freak accidents and circumstances, as well as bad decisions by the genpop were my job security.
Click to expand...
Thank you for explaining your experiences, the perspective of a first responder is something I think many need to hear.

I know how unlikely it is that someone will be seriously injured by a residential service drop, or by household current in general, but I also know how dangerous it can be, hence the reason I try to urge anyone who is not qualified to stay away. Far away. Same reason I tell people to avoid DIY tree work.

Electricity is very dangerous, when not respected. My years in college, and my years working in the field handling lines taught me that. I am not a Master Electrician like @Shadowscape, I’m only a Journeyman, but I still consider myself reasonably knowledgeable, especially since I do have a college electrical degree.
 
Reach said:
Thank you for explaining your experiences, the perspective of a first responder is something I think many need to hear.

I know how unlikely it is that someone will be seriously injured by a residential service drop, or by household current in general, but I also know how dangerous it can be, hence the reason I try to urge anyone who is not qualified to stay away. Far away. Same reason I tell people to avoid DIY tree work.

Electricity is very dangerous, when not respected. My years in college, and my years working in the field handling lines taught me that. I am not a Master Electrician like @Shadowscape, I’m only a Journeyman, but I still consider myself reasonably knowledgeable, especially since I do have a college electrical degree.
Click to expand...
Thanks for saying that. I totally respect the knowledge you guys have and my lack there of. I feel like, if I was to look at this conversations as an outsider, I would be much less concerned about the lines due to the education I received from the thread. But my gut tells me that’s not necessarily a good thing applied to the masses. I also recognize this is a thread for professionals having grown up conversations. If this was a local educational event for my local tree folks I’d be screaming for you to please don’t say anything more. Lol. Does that make sense? The already have no respect for the electrical potential
 
Shadowscape said:
I was dismantling a motor control center at a defunct sawmill. It operated on 480 volts 3 phase. I pulled out a bucket on its track, which disconnects the clips on the back from the buss bars. Stuck my hand in and got a dandy shock. Turned out the clips on the back of the bucket had broken and some idiot had wired the starter leads directly to the buss bars by drilling holes in the bars and bolting the leads to them.
I also found fuse boxes with steel bars in them in place of fuses, and contactors held down with small wedges of wood.
It was no wonder the mill had gone out of business. I assume it was managed with the same mind set.
Click to expand...
We used find Pennies shoved into the old fuse panels in the box in certain neighborhoods. I always wondered who drew the short straw on that deal. Also creative work arounds when the power company took the meter. Some crazy stuff people do. One time whatever they did resulted in why aluminum siding getting energized and the chain link fence also. The codes people weren’t too happy.
 
Steve Connally said:
Thanks for saying that. I totally respect the knowledge you guys have and my lack there of. I feel like, if I was to look at this conversations as an outsider, I would be much less concerned about the lines due to the education I received from the thread. But my gut tells me that’s not necessarily a good thing applied to the masses. I also recognize this is a thread for professionals having grown up conversations. If this was a local educational event for my local tree folks I’d be screaming for you to please don’t say anything more. Lol. Does that make sense? The already have no respect for the electrical potential
Click to expand...
What you say makes perfect sense, and I won’t ever tell a general public that power is not concerning. I consistently tell them to STAY AWAY for a reason. I explain that I am a highly trained and experienced person, and therefore I am qualified to not only work on the lines, but also to tell them how hazardous the work is.

In a group of professionals like this, I try to qualify my remarks, and I hope my first comments did that well enough. Perhaps I should have added a disclaimer to all the remarks I made, as you do make a good point - people will take one comment out of context and listen to only the parts they want to hear.
 
Steve Connally said:
We used find Pennies shoved into the old fuse panels in the box in certain neighborhoods. I always wondered who drew the short straw on that deal. Also creative work arounds when the power company took the meter. Some crazy stuff people do. One time whatever they did resulted in why aluminum siding getting energized and the chain link fence also. The codes people weren’t too happy.
Click to expand...
To energize the siding and fence, one must somehow break/disconnect the neutral between the main panel and the transformer. I’ve seen that happen, when I was wiring expensive houses (this was a house we built and I wired - https://www.houzz.com/hznb/projects/fox-hill-farm-pj-vj~119429) we got a call from an angry GC, the gutter guys showed up to work on the copper spouts, and got blown off an aluminum ladder when he grabbed an energized rain gutter. About the same time, the HVAC guys called to yell about an energized A/C unit next to the house.

Once we got there and figured out the problem, it was determined that someone, probably an excavator, broke the buried neutral line. Power company strung a temporary line and all problems went away.
 
Reach said:
What you say makes perfect sense, and I won’t ever tell a general public that power is not concerning. I consistently tell them to STAY AWAY for a reason. I explain that I am a highly trained and experienced person, and therefore I am qualified to not only work on the lines, but also to tell them how hazardous the work is.

In a group of professionals like this, I try to qualify my remarks, and I hope my first comments did that well enough. Perhaps I should have added a disclaimer to all the remarks I made, as you do make a good point - people will take one comment out of context and listen to only the parts they want to hear.
Click to expand...
No I think I what you said was enough. I just woke up today with the unfortunate feeling like I need to voice my opinion. I try to not do that most often. I’m out gunned and can only provide anecdotal sorties. Lol.
 
Steve Connally said:
@Shadowscape I don't pretend to have the knowledge you have but what I can tell you about is my 30 year history as a Paramedic and 25 years as a firefighter. I can tell you stories about the cardiac arrests and near electrocutions from 110. I can also discuss the requirements for wooden ladders to be nonconductive. When I first came in the FD wooden ladders were still a thing and the maintenance to keep them compliant was brutal for the rookie. Again I don't wanna try to say I know better but I have seen things that led me to respect electricity in any form a little more. I personally wouldn't recommend or actually jamb anything into an outlet under any circumstances. It's just not a prudent gamble. I also would not bet my life on the house drop covering. The linemen ground the truck and wear insulated gloves to handle them. Probably a good practice and done for a reason. Just my opinion that things that can probably kill you will eventually have the rite circumstances to do so. Not my mission to accelerate the process. The space I personally choose to operate in is to not deal with things I'm not an expert in and not take chances I can't justify. Its worked out pretty well for the last 50 plus years. I almost walked off a job site the other week because they wanted to lift a house feed to get the crane under with a pole saw extension with aluminum caps. Every time they lifted the wire it arched in the tree it went through. I impolitely told them if anyone does it again I'm leaving and they can kill themselves after I leave. No desire to do CPR on anyone again. I've done that thousands of times and I retired for a reason. I hear what you guys are saying but from a general approach, is it better to have these rules out there for the entire industry or to take for granted people will use the discernment those of you who are trained would use in a similar situation? I'd propose removing the option to handle the line would cause the greatest good for the most people. I'm also biased based on previous work history and the fact freak accidents and circumstances, as well as bad decisions by the genpop were my job security.
Click to expand...
@Steve Connally
Steve,
I don't want to come across as some who says household electricity, or service drops are something you don't need to worry about. That was not my intent. I guess what I was getting at was that we train and educate arborists with fear rather than understanding. Take the service drop that arced when lifted you were talking about. The fact that it arced scared you. Where was it arcing? At the house? The pole? Or one hot line to another, or neutral? Certainly it was not arcing to the pole they were lifting it with. Maybe at that spot, but not to the pole. Wherever it was arcing it needed repair. You said it was arcing in the tree it went through. I can assure you it was not arcing to the tree, but to the neutral or the other hot wire, and probably had lots of cracks in the insulation. Might have popped a fuse down the line if they kept it up.
I too have been involved in many electrocutions over the years as I also was a coroner in the Chicago area. Saw way too many. Mine were all dead.
But on to training. Why not train arborist who work around service drops and other power lines what, where, why and how rather than telling them to just stay away? If you lift a service drop with a fiberglass pole or a wooden pole, you are not going to get hurt. Not one bit. If it is arcing, the drop has a problem that needs to get fixed, but it is of not danger to the person poking at it with the pole. Might cause a fire if it is arcing at the house. May blow a fuse down the line someplace. But no one is going to die or get shocked.
Electricity is dangerous, but it is way more dangerous to people who don't understand it and fear it because they don't know what they are doing, and what is safe and what is not.
120 volts has very little potential behind it to overcome insulation. Prime example: You can put on a pair of those thin dish washing gloves people wear when washing dishes and with that put your hand on a bare 120 line. You can put on a pair of those old rubber goulashes with the buckles we wore as kids and that is enough insulation to keep you from getting a shock. Yes 120 volts can kill you quite easily because it does fuck with your heart.
I'm not a proponent of telling people to just stay away. But I am a proponent of letting people know what the possibilities are and how to be safe around what they need to work around. Why you can lift a service drop with a pole and be safe or drop a small limb on it and nothing is going to happen, or if you are in a tree and accidently bump into it nothing is going to happen. A fellow, or lady working in a tree near a service drop that understands that if they bump into it, it is not going to hurt them is going to be safer than a person who is scared that if they get near it, they might die. That person is not going to work very safely at all because that idea they are in danger will not allow them to be comfortable.
Questions that should be addressed and taught to all arborists that work near a service drop:
What will cause me to get a shock from it?
What might cause me to be killed by it?
What can I do to keep from getting a shock? And why don't I get a shock that way?
Simple questions to explain and answer so they have an understanding of 120 volt service drops.
Not, Stay away because they can kill you, which leaves them with no understanding and just a lot of fear. Bad deal all around.
Primary lines and transmission lines are another story and should be left to people who are trained in that field, but service drop electricity should be included in basic arborist training so they can work around them safely and efficiently.
Every house has 120 volt extension cords going to lamps and things. We handle those without giving it a thought. The service drop is the same damn voltage, yet we are ingrained with the fear that they are somehow more deadly. That is just bullshit. I repeat, bullshit. If you were at your friend house and he went to move an extension cord and when he grabbed it, it arced and snapped, would you tell him you were going to leave before someone gets killed?
The service drop is just a fat extension cord with two 120 volt wires instead of one.
ps: I'm not fighting you or your thoughts, just trying to make it a safer thing for those who work around service drops. If someone is not comfortable around them, they should be cautious, and, they should take some training so they understand them better. But not from an outfit that trains arborists because all they will get is, STAY AWAY or it will KILL YOU bullshit. That doesn't help anyone.
 
Last edited:
You must log in or register to reply here.

New threads New posts

Back
Top Bottom