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View Full Version : Utility Locator in need of some answers from the experts.



usmcss
02-22-2009, 06:38 PM
Hello Everyone,

I am a Utility Locator and have a couple questions I hope you wouldn't mind answering. I am getting a lot of conflicting answers when it comes to how much voltage certain lines carry and thought this would be the best place to clear it all up.

My questions are; how much voltage does a single phase and a 3 phase carry that runs in the back yards of homes to transformers? What is a 750 and how much voltage does it carry? Is there a difference between an a phase or b phase or c phase and a single phase? And finally what is a switch gear used for?

Can you get shocked from a neutral Wire?

If there is a place you can direct me to for the answers that would be great as well. I have a lot of respect for you guys and the job you do.

Thanks in advance!!

Semper Fi

Bob

shrek
02-22-2009, 07:59 PM
750 is a size of wire, as for voltage depends on the system voltage and when your talking three phase your talking line voltage and when you are dealing singal phase your talking phase to grd voltage and yes if the neut is open you can get shocked by it

electric squirrel
02-22-2009, 08:43 PM
Your pretty vague there ape...... get out your books and give the guy a good answer in working layman's terms, try explaining it so a guy who don't build power lines can understand it,,,,,, if you need I'll help you guys E.S.:cool:

usmcss
02-23-2009, 07:57 PM
Thanks for the replys but I am still a little lost. What I've been told is that the single phase is around 4KV and the 3 Phase is 3 4KV Cables?

750 is three 3 phase cables in one? Is this even in the ball park?

Thanks.

Semper Fi,

Bob

Pootnaigle
02-23-2009, 08:33 PM
UMMMMMMM No 750 is a wire size Kinda like your shoe size, not a voltage its usually describing ( in your case) the size of each buried conductor. Each of these conductors constitutes a phase. and each has a voltage. So assuming you are working on a 4ooo volt circuit( I bleve you mentioned that) the phase voltage for each a b and c would be measured approx 2400 volts to ground and 4000 from a to b or c. or any combination thereof. You also asked about switchgear I bleve. This is a cabinet that allows for isolation of a section of buried cable. It may house switches or primary terminations of such a kind as to allow a portion of the circuit to be fed from more than one source or to isolate it from all sources.There are many different voltages used across the country. The local utility would be your best source of info as to what voltages you are dealing with. It may very well change from one geograpical location to another. In any case its not sumpin you wanna be foolin wif.Special saftey equippment and devices are required to handle it safley. And yes a neutral can cause you much misery. My advise is to leave it to the pros. But feel free to stop one of em and ask any questions you may have, They may can help enlighten you

shrek
02-23-2009, 08:41 PM
It sounds like your system voltage is 4160 that means if you measure across any two phases you will get 4160 a-b, a-c, b-c or in singal phase you would get 2400 a-net, b-net or c-net. So then the netural is a phase that is held at grd potential so if that becomes open or cut if you will you can get full phase voltage across the open, and as for the 750 is that primary cable or sec 750 is the size in circular mills it sounds like it could be an armor type cable hey squirrel how did i do the second time, I am about to top out I should know some of this ha ha but still alot to learn

wtdoor67
02-23-2009, 09:05 PM
Buddy, just go to your local library and check out the "Kurtz Lineman and Cableman Handbook". It'll give you a general idea of what you're dealing with. If you care to buy one you can go to Ebay, Barnes and Noble or maybe Amazon and buy a good used one for maybe 20 dollars or less. Try to get maybe a 6th addition or any I guess.

Most of what we tell you here is gonna just confuse you. If you know a local lineman that works for the power co. or such get him to explain things to you.

If you don't get any satisfaction then maybe we can explain things to you.

Talking about wire sizes etc. will maybe confuse you also. Try some places online and I bet you can get some good info there.

mx-5
02-23-2009, 10:09 PM
bob,all you need to know is that stuff will kill you and quick...stay away from it.:eek:

usmcss
02-24-2009, 06:14 PM
Guys I really appreciate all the answers; thank you all for taking the time to reply.

I will certainly check out the book wtdoor; thanks!

I have no intention of ever messing around with anything electric; we ar not authorized to access anything that deals with Power. We can only access Phone, Cable Tv, and Gas. All we do is hook up to the outside of the meter, Switchgear or transformer. I just wanted to have a little knowledge of what I am locating.

Thanks again guys!!!

Semper Fi,

Bob

T-Man
02-26-2009, 08:29 PM
How much voltage does a 3 phase carry that runs thru the back yards of homes?

This depends on the source station voltage, it can be 2200/3810 2400/4160 4800/8320 7620/13,200, 14,400/24,900 and on up all of which are primary distribution voltages and can be different numbers in different utilities no matter.
Each voltage I listed has two numbers the first number gives the phase to ground/neutral voltage, the second gives the phase to phase voltage. These are all what are known as Wye systems and they will always have the two different numbers. On delta primary systems there is only one number which is a phase to phase voltage. In either Wye or Delta there three separate Phases and to identify each they are given a name so A, B and C are as good as it gets. Sometimes all three run thru the back yard and sometimes only one will do the trick, it all depends on the balance of load and the design of the area to be fed. In order for the Wye system to work there is a neutral wire, sometimes Wye systems are referred to as 4 wire systems, three phases and a neutral. The neutral carries the unbalanced load. . .so if you got between the two ends of an open neutral you may experience real close to phase voltage depending on how unbalanced the system is at the time, whichby the way is not good!. So the rule is to never assume the neutral is a safe de-energized wire, it’s not!

750 is a cable size and usually found on secondary circuits due to It’s size, Remember Ohm’s Law the lower the voltage the higher the amps, the more amps you run thru a cable the bigger the wire needs to be, hence the 750 on secondary. Primary distribution on my system is usually #2 aluminum, or main line may be 500 MCM, a 750 primary on my system is most likely to be found in an underground lead covered cable system running thru vaults and duct in a metropolitan area. Or maybe in a pipeline transmission either in the ground up a right of way or on some 138 K tower lines. (Which are a low voltage for most) usually transmission lines start at 2156MCM which is a little bigger than the handle of a baseball bat if ya catch my drift?

Oh boy switch gear. . .this can be a few things like what we call a switch fuse unit where the main line primary or sub transmission goes thru the unit controlled by switches on either side and fused lines bucking off to feed customers tapped of the bus. Sometimes switch gear is customer owned and has a line coming into a switch compartment and up to a bus then in the adjacent cubicles there are meter compartments, fuse compartments maybe a bus tie compartment and another fuse compartment and maybe one more inbound line compartment. I know there is a lot here but draw it out and see what you get.

I’m not a professor on this stuff just 40 years working, dispatching and teaching it. The reason I took the time is these are good questions, by what I see is a young lad trying to do a good job and I’d like you to stay safe doing it. That goes for the rest of you all. Work safe

I was not able to post this in the forums till they let me in today. . . Hope this helped.
K-30;)

electric squirrel
02-26-2009, 09:20 PM
It sounds like your system voltage is 4160 that means if you measure across any two phases you will get 4160 a-b, a-c, b-c or in singal phase you would get 2400 a-net, b-net or c-net. So then the netural is a phase that is held at grd potential so if that becomes open or cut if you will you can get full phase voltage across the open, and as for the 750 is that primary cable or sec 750 is the size in circular mills it sounds like it could be an armor type cable hey squirrel how did i do the second time, I am about to top out I should know some of this ha ha but still alot to learn

Yup, much better!!! Now he also wanted to know IF there is a difference between a,b and c phase. Not riding your ass or nothing,(your ready to top out, you gotta be the teacher now,just like I had to do) but try explaining that.Hint ,sine wave.Your right too, lots to learn, I learn something new everyday,,,,, E.S.

glover
04-15-2009, 06:34 PM
on all military installations, they use paper lead cable. a lot of it is underground and is used primarily because a nuclear blast has the effect of distrupting normal power lines, lead has some protection from this and is why it is used in military applications, I know this from some work in florida at military bases, paper lead usually requires a cable splicer to work hot lead in making connections. and is becoming a lost art. as with any type of electric cable or lines. know what you are doing and why is not only important but you have to bet your life that what you are doing is right. you don't get a second chance. webmaster if any of this info is against the protection of our country please do not forward or repeat this to anyone except those who have a need to know.

glover
04-15-2009, 06:37 PM
on all military installations, they use paper lead cable. a lot of it is underground and is used primarily because a nuclear blast has the effect of distrupting normal power lines, lead has some protection from this and is why it is used in military applications, I know this from some work in florida at military bases, paper lead usually requires a cable splicer to work hot lead in making connections. and is becoming a lost art. as with any type of electric cable or lines. know what you are doing and why is not only important but you have to bet your life that what you are doing is right. you don't get a second chance. webmaster if any of this info is against the protection of our country please do not forward or repeat this to anyone except those who have a need to know.

work it hot or ground it out!!!!

Divemaster
04-22-2009, 11:18 PM
For those who want to know: the best way to locate electric cables is not to direct connect to the ground or the neutral. Reason: everyone and their brother connects to our ground. Hence, you may pick up telephone, cable tv, gas and water not to mention the electric. Best and safest bet is to hook your locator up using the induction clamp around the wire you are attempting to locate. It will help in making a more accurate locate, you won't have as big of a problem with phantom signals, and it will also be a better way in making it home at the end of the day:)! Another idea is to go to a locating school. In Nebraska, our Diggers Hotline, has a free school once or twice a year, your on-call may do the same. Radiodetection, and Metrotech both have good seminars if you can find one.