[rockman413]

Hi there,
I'm just new to this. I guess the underground electrical cable, such as the cable from your garage to your front gate door in a single family house, will be put into a pvc conduit so it won't hurt you .
However I guess maybe years goes by, that conduit can get broken especially if there're trees nearby and water can get into the conduit and touch the electrical cable , and may damage the surface of the eletrical cable , and if it's raining so human nearby can touch electricity via water. Let me know if I'm wrong? what's the caution for this kind of underground cable?

 

[joed]

Simple to protect from harm by installing a GFCI on the line BEFORE it goes underground.

 

[SW Dweller]

Schedule 40 electrical PVC will take centuries to break up in normal dirt. If the line is in conduit no worries as for at least until the next century.
All electrical conduits get water in them. Just the way it is. Most current wiring has resistance to moisture.
All outside circuits should be on GFCI protection.

 

[viper]

Any underground conduit is considered a "wet location", and likely already a pool of water in there just due to condensation. I have personally witnessed a very live 240V pump switch floating in a pit, still doing work! The whole idea of "grounding" is that the juice to your place wants to get back to ground. The ground......

While anything is possible, I probably would not lose sleep over it.

 

[Davejss]

 

[C'est Moi]

Hi there,
I'm just new to this. I guess the underground electrical cable, such as the cable from your garage to your front gate door in a single family house, will be put into a pvc conduit so it won't hurt you .
However I guess maybe years goes by, that conduit can get broken especially if there're trees nearby and water can get into the conduit and touch the electrical cable , and may damage the surface of the eletrical cable , and if it's raining so human nearby can touch electricity via water. Let me know if I'm wrong? what's the caution for this kind of underground cable?

Your analysis sounds more like a worry that you have. First off, water will not harm the wire if the correct wire is used. For example, UF cable can be laid into the ground without any conduit. If you use conduit then the wires inside are rated for wet locations. The odds of someone getting hurt are small but it certainly can if, for instance, someone dug thru the conduit and cut the insulation.

The only time that I have seen issues with an underground feed where someone got hurt is when a pool was involved and there were illegal splices made in the power to the pool panel. Things do happen but not that often and there is usually human error involved

 

[A Little Short]

Any underground conduit is considered a "wet location", and likely already a pool of water in there just due to condensation. I have personally witnessed a very live 240V pump switch floating in a pit, still doing work! The whole idea of "grounding" is that the juice to your place wants to get back to ground. The ground......

While anything is possible, I probably would not lose sleep over it.

Not true at all. The "juice", as you call it, is just making a loop through the load and returning to the source. Ground or grounded is just the service neutral being grounded to a ground rod (or other electrode) for surges & lightning strikes. A fault/short anywhere is trying to get back to the source such as the main panel or transformer. The ground in a circuit is tied to the neutral at the main panel or main disconnect. Any short/fault down stream of that between hot and the ground wire will travel back to the panel neutral causing a short and trip the breaker.
The dirt/ground has nothing to do with how current flows.

The term "ground" is very confusing to those not familiar with how electricity works (and some that do know).

 

[PBR Street Gang]

You don't need conduit, just bury it at least 2' and put it on a GFCI breaker.

 

[hornetd]

The whole idea of "grounding" is that the juice to your place wants to get back to ground.

The whole idea of grounding is based on the common misunderstanding, amongst people not involved in the generation transport and delivery of electricity, of were current is coming from and were it will go back to! In most uses the term grounding is a misnomer. Electricity does not want to get to ground. It wants to go back to it's source. The secondary distribution transformer of your supplying electric utility is were the current was produced and that is were it will naturally return to.

The National Electric Code reads

"250.4 General Requirements for Grounding and Bonding.
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding.
Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
(2) Grounding of Electrical Equipment. Normally non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.
(3) Bonding of Electrical Equipment. Normally non–current carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.

What I suspect you are actually referring to is:

(4) Bonding of Electrically Conductive Materials and Other Equipment. Normally non–current-carrying electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.

Ground fault current was what some of the earliest investigators and users of electricity called current escape. They weren't wrong. When current escapes from an electric circuit; through some failure, or fault, of it's insulation; it will still tend to flow back to it's source by all pathways available to it. If all those unintentional pathways are deliberately connected back to the source then any fault in the insulation of an energized conductor will allow sufficient current to flow back to the source and cause the circuits Over Current Protective Device (OCPD) to open thus deenergizing the inappropriately energized materials. The loss of the use of the loads normally supplied by the deenergized circuit will cause someone to repair the insulation or replace the defective portion of the circuit thus clearing the fault. Once the fault has been cleared the effected circuit can be reenergized and the loads connected to it can once again be put to use.

The earliest users of electricity used the earth as one of the conductors of circuits. From the day Samuel Finley Breese Morse sent the first telegraph message to Alfred Vail; who is the man who had devised the "Morse Printing Telegraph Code," until the telegraph was last used ~1964 the land line telegraph system used the earth as one of it's conductors. Right through today the electrical utilities of the United States and Canada use the earth as one of their distribution network's conductors. Because of the danger that practice was found to cause when used in premise wiring systems it was not applied to a structure's inside wiring. Inside of buildings only insulated conductors are used to carry normal system current. All of the uninsulated conductive objects that are likely to become energized, thus becoming an unintended current pathway, are bonded together and to the Grounded Conductor of the Utility's lines so that escaped current can flow back to the source non destructively. Much of the confusion around this is caused by the historic and ongoing use of the Earth as a circuit conductor. As a result of those practices the conductors which carry the escaped currents back to whence they came at the utility's distribution transformer, are called Equipment Grounding Conductors (EGCs). Until a consensus develops among all major authorities on electricity that such language is inaccurate we will be suck with the name Equipment Grounding Conductor. Now you know that it is actually an equipment bonding conductor which bonds all of the normally non current carrying conductive parts of the electrical system to the supplying utilities distribution transformer.

Tom Horne

 

[Missouri Bound]

I doubt I would ever bury cable instead of wire inside of conduit.
If you bury a cable and it has a nick in it from a shovel or just a careless install, that nick will eventually lead to cable failure do to moisture.
If you use conduit then you have the flexibility to change the circuit amperage if your needs change.

 

[hornetd]

water can get into the conduit and touch the electrical cable , and may damage the surface of the electrical cable , and if it's raining so a human nearby can touch electricity via water

A couple of things might help you understand the risk of electric shock in that manor are;
fresh water is not a good conductor of electricity. That is both a blessing and a curse is some ways.
The voltages used in home wiring are too low to force a harmful flow of current to anyone who is not very close to the fault in the insulation of a conductor in that conduit.
Electricity has to have a way to both come and go to harm you at those voltages. For that to occur 2 points on your body must be in contact with 2 separate points which have a difference of potential between them. Difference of Potential is measure in volts. The 2 points would be said to be at different voltages.
The voltage difference between the 2 points on your body that is in contact with the different voltages must be high enough to overcome the natural resistance of your skin and whatever clothing you are wearing. 30 milliamperes must flow between those 2 points and, in order to electrocute you, it must flow through the upper portion of your chest cavity so as to disorganize the electrical signals that your body uses to organize the beating of your heart. If that all happens then your heart will fibrillate, which means to not contract and relax in the particular way it needs to in order to pump your blood through your longs and then off to your brain and other vital organs. At the voltages used in your homes wiring that set of circumstances is not very likely to come about.

But there is a different and not uncommon fact set then you don't even need surface water to get shocked and possibly electrocuted. When an electrical transmission or distribution line is in contact with the earth the current will be dangerous much further away than it would be at the voltages produced by your homes distribution transformer. Distribution voltages are high enough to cause the current to flow through the earth for quite a distance before it has spread out far enough to no longer cause a dangerous difference in potential between different points on the surface of the ground. Closer to the point of contact with the earth much more current will be flowing through a much smaller area of dirt. That causes a dangerous voltage to exist across a distance as short as your walking stride. That difference is called Step Potential. The difference in voltage across one step can be enough to kill you! That is why you should always keep your self at least 2 intact spans of the wire between adjacent poles away from the point were it is touching the ground. That is not always easy to see. A downed wire in contact with a metal fence or road guard rail will energize the entire length of that conductive material thus extending the danger much further than the obvious contact point of the wire itself.

The take away is to never approach a downed electrical wire. under no circumstances should you touch it or come in to contact with anything it is touching including the earth itself for a surprising distance away from the wire. High voltage lines are not insulated. Instead they are isolated from the rest of the environment by being supported on insulators made to resist the flow of any current through them at the voltage they were made to withstand. If the wire is no longer on it's insulators then anywhere along it's length or on the ground for quite a ways around it is hiding instant death.

Tom Horne

 

[viper]

Not true at all. The "juice", as you call it, is just making a loop through the load and returning to the source. Ground or grounded is just the service neutral being grounded to a ground rod (or other electrode) for surges & lightning strikes. A fault/short anywhere is trying to get back to the source such as the main panel or transformer. The ground in a circuit is tied to the neutral at the main panel or main disconnect. Any short/fault down stream of that between hot and the ground wire will travel back to the panel neutral causing a short and trip the breaker.
The dirt/ground has nothing to do with how current flows.

The term "ground" is very confusing to those not familiar with how electricity works (and some that do know).

Thank you. I very much understand grounding and said what I said based on the discussion. By your explanation, we could basically remove all grounding as it serves no purpose at all! The word is "potential".

But in any case. Did we just dig a hole and cut the neutral, or are we dreaming about how the water degraded the cable sheath because the electrons got away?

I have learned not to go into detail here. The basic sum is "I would not lose sleep about it".

 

[viper]

I guess since people are attacking me, I will clarify something, and no, I don't want to walk down a long road about it.

I said "it wants to get back to ground!", and people lose their minds. When in fact I am 100% right! Because EEs decided over 100y ago that floating the neutral was a bad idea for many reasons. So it was BONDED or REFERENCED to the EARTH. This means that any voltage that is created at a plant is REFERENCED to the EARTH, and all pole pigs are also REFERENCED to EARTH.

All I am saying is some imaginary cable leakage 2ft down in a trench has about zero incentive to reach up in a tree and zap poor Johnny. Now if you want tot hold both ends of a broke neutral, you will not need any coffee that day!

 

[zanydroid]

If you have underground service, it's most likely going to be SCH80 PVC buried a couple feet down. This is probably unfused at the transformer side so you have the full power of the utility transformer available for a fault, there's a lot of it running down the yard of all houses that have underground service. It's most likely something very burly, IIRC at least 2" conduit for 200A service. Anyway, conduit with this level of protection is deployed at high density in residential areas, and people seem to be OK with it.

Now the branch circuit that you add yourself will not be done to the same level of scrutiny as your service. But still do it to the same due diligence -- bury deep enough, with proper soil preparation, expansion joints, etc, conduit is probably fine. It can be oversized for more protection. It can be GFCI protected for more protection.

 

[hornetd]

It can be oversized for more protection.

If you want to protect the installation further it is usually cheaper and far more effective to use stronger conduit than to use bigger conduit. If you have some reason to actually be worried about something damaging the conduit go up to schedule 80 heavy walled PVC. There is a reason that when conduit needs additional protection the designers first look is how many of them are there. With only a couple you use stronger walled conduit. When you get much above 3 going to and from the same place you resort to duct bank and encase the conduit in concrete.

Tom Horne

 

[zanydroid]

If you want to protect the installation further it is usually cheaper and far more effective to use stronger conduit than to use bigger conduit. If you have some reason to actually be worried about something damaging the conduit go up to schedule 80 heavy walled PVC. There is a reason that when conduit needs additional protection the designers first look is how many of them are there. With only a couple you use stronger walled conduit. When you get much above 3 going to and from the same place you resort to duct bank and encase the conduit in concrete.

Thanks for the info. Actually I have a hard time imagining what at a residence can completely shatter buried SCH80 to the point where the conductors will start taking damage. I guess maybe some slow damage over time by nature can accumulate; that's kind of hard to think about if it hasn't been explained to you since it operates at such slow time scales.

 

[FrodoOne]

I'm just new to this. I guess the underground electrical cable, such as the cable from your garage to your front gate door in a single family house, will be put into a pvc conduit so it won't hurt you .
However I guess maybe years goes by, that conduit can get broken especially if there're trees nearby and water can get into the conduit and touch the electrical cable , and may damage the surface of the eletrical (sic) cable , and if it's raining so human nearby can touch electricity via water. Let me know if I'm wrong? what's the caution for this kind of underground cable?

The situation (badly) described is roughly the same as that of a bird which "perches" on an an 11000 V (or any other "High Voltage") cable.
As long as the "individual" does not touch anything which is at a different potential, that individual will experience no problem.

If a fault occurs on any cable - so that there is a connection from the Supply "Line" back to the "Source", current will flow and create a "potential difference" across the Impedance (mostly, resistance) involved.
With a High Current, the Circuit Breaker should be "activated"
With a Low Current (leakage to Ground), any GFCI/RCD/RCBO should "activate" - which is why such devices should be at the "Panel".

If a "leakage" from the "Supply" to the "Ground-Return" does occur and
the "Protection Device" does not activate
there could be a potential difference across the (wet) ground between the point of leakage and the actual "Ground-Return" point
with the Potential Difference being many volts between points of "Wet Ground" apart.
In these unlikely circumstances, an individual would be quite safe standing still but may experience the difference in potential as the individual stepped away from the source of the leakage towards the "Ground-Return" point.

With the entire video being worth viewing from beginning to end, in the hope of your obtaining some better understanding of this, please see

from 34:50 to 44:12

 

[Luke M]

Utilities routinely direct bury 15kV cables (including on residential properties).

 

[A Little Short]

Thank you. I very much understand grounding and said what I said based on the discussion. By your explanation, we could basically remove all grounding as it serves no purpose at all! The word is "potential".

But in any case. Did we just dig a hole and cut the neutral, or are we dreaming about how the water degraded the cable sheath because the electrons got away?

I have learned not to go into detail here. The basic sum is "I would not lose sleep about it".

I never said it served no purpose, I said it doesn't effect how current flows, pertaining to functionality of the electrical service. There can be current flowing in the earth but the resistance is so high it is not a good path back to the source, which is the transformer. Power companies/utilities ground/earth their systems as there is high voltage and grounding works well for them. A ground rod, or other grounding system at a dwelling has little effect on anything as the voltage is low compared to the utility.
Since you said "The whole idea of "grounding" is that the juice to your place wants to get back to ground. The ground...... "
It didn't tell me you knew how current flows or what grounding was for.
Great if you know, but I wouldn't make statements like that.
I've heard people say they just drove a ground rod and run a ground wire to something that didn't have an equipment ground, thinking they just made it safe by doing that.

 

[seharper]

I'm never going to get behind saying "power wants to return to ground".
Saying "power wants to return to SOURCE" is correct, and remains correct in all the conditions you intend, and is also correct in every other condition as well.

I said "it wants to get back to ground!", and people lose their minds. When in fact I am 100% right! Because EEs decided over 100y ago that floating the neutral was a bad idea for many reasons. So it was BONDED or REFERENCED to the EARTH.

That's only true if everything is working properly.

"So what?" you say. "Everything is working properly most of the time." But now ask yourself why we bother with grounding and bonding in the first place? It is entirely pointless if everything is working properly.

Grounding is there for the times when it isn't.