One of the only great things about the Internet is the wealth of information that Mike Holt provides, free of charge. Thank you, Mike!

Great discussion Mike. Thanks for all you and your guests work.

Thank you for your passion explaining these mostly unknown yet important concepts. And putting it out there for free.

@MikeHoltNEC

Жыл бұрын

Thank you for noticing.

Hello Mike. Thank you for putting the Neutral to Earth voltage into perspective. A truly amazing presentation. Thank you.

Crystal clear presentation. Thank you!!

Thanks for this awesome presentation. Now I know how to think about and describe the 10v NEV that I am seeing at my rural location (enough to hurt, but not kill).

Great presentation and explanation of NVE Mike, i really learn how it measured the NEV to a ground referencing the amperage load on equipment house I'm an a fire alarm technician on a growing industry and safety thank you and God bless you all

I thank God for you mike !

Mike you've been such a blessing throughout the years...I was first introduced to your books back in 2001 I was on my 2nd year of apprenticeship. May God continue blessing you and your family. 🙏

@MikeHoltNEC

2 жыл бұрын

Thank you and now you're an adult! My wife is waiting for me to grow up...

Mike thanks so much for sharing your vast knowledge of the subject with a smooth articulate confident delivery that makes listening to your classes thoroughly enjoyable.

@MikeHoltNEC

2 жыл бұрын

Thank you for the kind words.

Mike your videos are great. I work for a large utility in NC and I am a protection and control tech. I have a great understanding of electrical fundamentals. It is hard for people to understand step amd touch potential so I understand your explanation.

@MikeHoltNEC

3 ай бұрын

Aww, thanks for the feedback.

Dear Mike, You are the best teacher on this subject. I use you are a reference over and over in my Ham Radio Videos. As a former Building Inspector, I always learn something new from you and your staff. Ham Radio guys like me often have many pieces of gear amounting to more than $10K. While watching and listening to your video (more than one time) i was finishing a 4KV DC power supply that can deliver 2 amps. I have to deal with ground neutral and the so called RF ground. Keeping each box at the same potential above ground takes a lot of work. Your graphic was very helpful too. Regards, Jim Heath W6LG

@richardmorholt1175

Жыл бұрын

N2WYJ, well said sir.

Every video of yours makes me smarter.

Mike, you have been an inspiration. I have learned so much about theory from watching your videos. Most amazing, you somehow have made reading National Electric Code fun!

@MikeHoltNEC

2 жыл бұрын

This makes my day!

Thanks Mike

Thanks for another great video, Mike. As a utility P.Eng. I've seen both cases over the decades: cause of high NEV on the utility side -- and the customer side. Regardless, it's ALWAYS a good idea for the utility to put its own house in tiptop shape. Avoid finger-pointing. Even if you measure less than 25 ohms at the pole or pad, improve it anyway -- get it down below 5 ohms! It might solve the customer's problem. But even if it doesn't, you're still cutting the step+touch voltage risks to your linemen and the public.

@mernokallat645

Жыл бұрын

Some countries in Europe require it to be under 2 Ohms.

Yo Mike you the man. I went through one of California's most intense apprenticeship programs which included 8000 hours OJT and 200+ books from basic theory to PLCs and everything inbetween. I still am completely lost on a lot of subjects especially grounding/ bonding, and "voltage". Those 2 subjects are the hardest to fully understand in my opinion. Thank you for the content and blessing up my confusion!

@MikeHoltNEC

2 жыл бұрын

Get my Bonding Library, book/videos. MikeHolt.com/Bonding

@ronald5728

2 жыл бұрын

8000 hours?

@driftingburrito895

2 жыл бұрын

@@ronald5728 yup, California requires more hours on the job to become an electrician than a cop

@ronald5728

2 жыл бұрын

@@driftingburrito895 Wow!!! That a lot of hours; almost 4 years. It's definitely more complicated than training to be a cop. lol

@Casualyoutubee

Жыл бұрын

Alaska is 8,000 too 😝

Your explanation is Excellent. I watch your programs from India

Thanks Mike…..Brian…..!

Will watch later but I KNOW when knowledge is precious 😌. Thank you fir you invaluable value.

Very interesting for a UK viewer where we do things differently than that! Almost bailed at the god-credit which felt jarring, but I am glad I stayed and it made me think! We have a 3-phase transformer for each area of housing, where the low side neutral is grounded, and 3-phase+N LV runs down every street with houses connected sequentially to one of the three phases and N. Single phase is about 230V but there is about 400V difference between my live and my neighbor's live! If I want temporary 3-phase I can talk nicely to my neighbors both sides and run extension cables.

Thank you.

In the marinas and boats specifically the issue we have there is the galvanic isolation systems which break the safety grounding conductor under normal operating conditions and then allow current to flow if there is a fault. The way they test to make sure that is working properly is to introduce a ground fault every 4 hours on the line. That is the required monitoring system required on newer boats. This however was in direct conflict with the requirement to have GFCI protection on the 30A/50A shore power cords as it would cause those to trip each time. The "fix" to this was you had to disable the monitoring system in the boats. Newer boats then started using ELCIs on their shore power inlets, and did away with the monitoring systems as well, so now there is no way by the average boat owner to know if the system is functioning properly. Our lake is a US Army Corp of Engineers lake and they have the requirement that there is no swimming around the docks to battle this issue, however nobody follows that rule. There are no "private" docks allowed on our lake, but you hear like Lake of the Ozarks with everyone having private docks the amount of accidental electrocutions is high due to very old docks mis-wired and falling apart. And that very well could be the neighbor down a dock or two that has the issue can can cause the harmful issues to exist on your dock. It would be great for a more in depth video on marinas and docks. When I had my boat in the marina I could always tell if my neighbors had electrical issues as my sacrificial anodes would get eaten up pretty quick and have to replace them so it didn't attack all the other metal on underwater on the boat. I would constantly check them and would change them in the water as needed as it was a large boat and you didn't haul it out that often.

@MichaelDHockenberry

2 жыл бұрын

Fascinating detail thank you

@ebaystars

Жыл бұрын

as boats dont use great power currents for heaters/lights (unless its a Russkie mega-yacht) etc can't they provide good quality 1:1 isolation transformers at each boat point and associated secondary ELCB/GFI trips? I wouldn't feel safe about my neutrals goin' all the way back to San Jose :-) as Joni Mitchel once said

@michaeljoncour4903

Жыл бұрын

perhaps boats could stick to low voltage dc, very little if nothing you can't get...

@mernokallat645

Жыл бұрын

Putting antiparallel diodes in the ground wire stops corrosion without breaking the ground wire.

I'm so glad you made this video sir

There you go Mike. You just answered 3 more questions. I used to wornder this all the time. Mike Congratulations. Hey mike I tell you I am your fan number 1 believe me.

@MikeHoltNEC

3 жыл бұрын

I am so happy to know that I'm making the world a little more clearer for you. God Bless!

Dear Mike, I am from Mexico and I really appreciate that you can teach many people. God bless you. I got the ultimate training library 👍🏼👍🏼 it going to be profitable because USMCA agreement 🤝🏼 🇺🇸🇨🇦🇲🇽

@MikeHoltNEC

2 жыл бұрын

I am so happy to hear the great news!

On the overhead Transmission lines you will have the 3 cables carrying your phases plus you will have your static ground on top of the poll and if the Transmission lines run parallel to any railroad tracks or underground piping it will have a mitigation cable to protect anyone working on those by preventing accidental discharge and it also helps prevent corrosion on any underground pipes.

@richardcranium3579

Жыл бұрын

Some transmission systems have a counterpoise wire buried between structures that are bonded to the overhead static wire. Not all transmission systems have it.

LOVE THIS VIDEO!!!!!!!!!!!!!!!!

Well done sir, thank you

Nice job and video like always

Haha, clamp a volt meter to a blade of grass. Your video's a very helpfull Mike, thank you. I've been a power plant operator and they taught me that 25 KV is the max. for powerplant generators. Has to do with air (H2) gaps and arcing over inside the generator. And indeed that grounding and bonding video is a great vid, vieuwed it many times.

@MikeHoltNEC

2 жыл бұрын

The blade of grass actually works great!

@johannesdesloper8434

2 жыл бұрын

@@MikeHoltNEC I've heard it before from certain kinds of trees in dry areas that root deep and ofcourse there are salts and water in the roots. I'll try it one day, living in the endless grasslands here.

@ebaystars

Жыл бұрын

we used to use long grass stalks to test if electric shock fences were working by holding one end and slowly sliding it towards the wire like a variable resistor I am not sure "use a blade of grass" is worthwhile advice other than a joke comment

Great videos & content Mike . I was working on a facility years back because of workers getting shocked . The neutral grid from the power company substation that was over 1000 feet and across the road was causing our grounding systems to energize and shock the workers on everything that was grounded.

@MikeHoltNEC

Жыл бұрын

That is true...

@phyde1885

Жыл бұрын

@@MikeHoltNEC I'm a retired EE from ITT,worked at COBRA as a QC Inspector for 3 years,then at RANK for a spell. Wished i had stuck more with the industry,but i'm self learning MORE PC and YOU to get a better grasp at this particular subject. Also did a summer as an Union Elec. So i've got my hands dirty in all over. I've always said,"I ain't Burnt a House down Yet !" And i did save a Life by 1 of my wire schemes. This is before i ever saw your channel. Instead of putting in GFCI sockets in a bathroom of a house i was re-wiring,i decided to protect the WHOLE Bathroom with 1 Breaker. His daughter was showering in the unfinished room,reached around for the switch,stuck her fingers in it and tripped it, and SAVED her LIFE !! When i found out,i about $#!t my Pants !! Makes me kind of fuzzy inside knowing i had done the RIGHT choice !! In this instance a GFCI would have been nowhere near to the job. Then when i was on the Union site,i had a Journeyman that had wired a 4 wire Delta transformer wrong. I jumped up at sat on it,and it LIT me UP ! DAM 440 SMARTS!! And he was suppose to be the Master !?! I know,i shouldn't have jumped on a Box and TRUST it,my BAD ! So it 's "YOUR" channel and vids that i'm turning to for that Knowledge in this Vid and Field i look to,to round out my other half i didn't get. P.S You have my Brother and sons name too !

This is a really excellent explanation of how multipoint grounding works

Praise Jesus !

Great!!

❤️, tks for sharing

thank you sir for a plesant lessons you have

Medium voltage distribution lines in Europe have only 3 wires used. The neutral at the substation is grounded through a variable inductance( Petersen coil or Bauch transformer). Resonant/ reactance grounding allows the reduction of ground fault current to 5 Amps or less and the line can be in operation under a single fault.

thanks mike , 30 years in the trade and nobody has ever explain to me about NEV or the .20v reading , i thought i wasn't getting accurate measurements or the instrument had problems reading very low voltage, i couldn't never understand y i was getting .20 to .22 neutral to earth .

Anyone viewing this to answer California system is that here the primary on singe phase is delta connected even though it may be a wye system with neutral connected and grounded at the sub. Having it Delta connected, helps with Harmonics.

Mike just an experience we had (we 15 yo boy , my father , and a friend master electrician )were stripping out uor old in preparation install new electrical service. Power wires were cut at the pole ,meter was removed but common/bare wire remained intact . As we were striping out “master cutoff “switch there was a 2’ arc and the whole street went dark. It turned out our house had the only ground on the entire street. In five minutes the electric company had 5 trucks on the street repairing grounds on every pole and house . Luckily no one was injured short of a laundry issue of brown underwear. If i understand you correctly basically all those readings were stray power loses . Now i see why Europe doesn;t use the same ground system as we do theirs seem to be a little safer. Still a bit confusing but i learned some thank you. I viewed a video on emergency/aux generator “grounding “ still sorting that out in my mind.

Simply Fantastic. The first minute already sets the success of this class. God Bless you greatly brother.

Mike, the biggest difference I’ve seen between two bushing and single bushing pots (distribution transformers) is the location of the neutral connection of the primary winding. One style pot (single bushing) ties the neutral end of the primary winding (H2) to the tank grounding lug and the the other style pot (two bushing) runs the neutral end of the primary winding (H2) out through the second bushing on top. The co-ops here use single bushing pots until they build a two (open Y open delta) or three (YY, Y/Delta, Delta/Delta) pot banks. The investor utilities here use two bushing pots on single installations and transformer banks. To myself the two bushing pot is less hazardous to the lineman working on the secondary side……If a lineman cuts the ground lug connection (single bushing) to the system neutral with the transformer energized he exposes himself to a difference in potential between the neutral (pole ground) and the now ungrounded end of the transformer primary winding (which will read at primary system voltage). The two bushing pot ties the neutral connection of the primary winding to the multi-grounded neutral in a configuration with less exposure to the lineman. Thanks for the videos!

Whenever I get to a new campground, I check the power pedestal outlet with a voltmeter to verify it is wired correctly. Then after plugged in measure my Converted bus to the pedestal to verify there is no voltage to create a hot skin condition. I need a better voltmeter to measure to the earth. The one I have is cheap and does not go down to tenths of a volt.

At one point in time while I was in the military, and doing lineman work, and someone described grounding to earth as NOT bringing the transformers, panel and grounding conductor’s to the earth potential. But bringing the local areas of the earth and grounded items to the potential of the items that were grounded to as near as same. So the multi point grounding is trying to make that neutral and the local grounding at the local earth - as close as they can be to each other. A few hundred feet away - that might have a different voltage potential - and that area would have its own grounding and the ground plane in that area would be the closest it can be due to the grounding in that area.

@MikeHoltNEC

Жыл бұрын

What you described is not the reason for a multi-grounded neutral system. But it's a nice story.

@NoName-OG1

Жыл бұрын

@@MikeHoltNEC WOW a A response from the man himself! By the way, I’ve been on your forum for a number of years, and watching all of your work which is 100% great! With the opportunity to bend your ear, I figured I’d say that. Anyway, that’s just the way it was described to me once upon a time. And always seemed to make sense. From a utility, or a lineman’s point of view. Richard, as you know, is much different than premise wiring and grounding. Edit The other item that was also described to me back then. But she may or may disagree. What is that without local Grounding, there technically would not be a fault path if a line fell and hit the ground… so on top of making the neutral conductor, the same potential as the earth in that area. It also created a method of clearing over current protection, if a line fell in that area. Again, you may disagree, but that is how it was described to me some 30 years ago. And it always felt like it made sense.

One issue I think NEV creates is with high magnetic fields in the house. Even with NEV around 1V, the neutrals will be directly connected to ground paths in the house (like pool equipment)...which creates a one-way current of hundreds of mA...which creates AC magnetic fields in the documented unhealthy range of >5mG. If you're far enough away from the circuit wiring carrying this current, then the magnetic field will drop off and not be an issue. For me, the circuit was running in the crawl space under the master bedroom and was subjected to the higher magnetic field during sleep.

One more thing the power or utility company can climb the pole where your transformer supply is and check each 120v feed to see if the current is equal .

Re: Ground Rod code in most states is a 10-foot rod into the ground.

Great video. Wish I could find the next one!

@MikeHoltNEC

3 жыл бұрын

Go to MikeHolt.TV

@miguelac6872

3 жыл бұрын

@@MikeHoltNEC Amazing Mike thank you again. I see you like a father Mike

@MikeHoltNEC

2 жыл бұрын

@@miguelac6872 Thank you and I do take what I do as a 'mentor' for the industry. Call 352.360.2620 to learn now you can take control of your career to the next level.

One of the main purposes for a multipoint ground system in the utility network is protection from lightning strikes.

neutral is supposed to be 0 relative to the earth. and we make it 0 by making the ground the same as the neutral side of the transformer. the reason you start to see voltage miles away on the neutral to the ground is because the voltage drop on the neutral (KxIxD) increases, while the ground stays the same. a voltage tester is designed to measure the relative difference between two points. in other words, the neutral miles away from the source, drops volts, while the ground stays the same. so the tester is showing you the difference @mikeHoltNEC please correct me If I'm wrong I don't want to mislead anyone I only want to clarify for myself and others

Great explanation. Thanks.

Just to refine the description of what happens during a phase to neutral fault: With long distances, there is considerable voltage difference between the substation and the point of fault for a distant fault. There is a drop in the phase, but in addition, there is a drop in the neutral. The neutral is pulled towards the faulted phase voltage. That increases the phase to neutral voltage of the other two phases _at the point of the fault_. The unfaulted phases do not increase (much*) in voltage with relation to the substation. By multi-grounding the neutral, the neutral becomes effectively a very large conductor, so the neutral can't be pulled towards the phase near as much. *really getting into the weeds - there is mutual inductance coupling, and the mutual can act as a transformer to boost the voltage some. But the effect is much smaller than the effect of neutral shift.

I have a tricky multiple choice question, hopefully someone with more knowledge can help me out A White/grey wire in a feeder circuit ________: A)Be bonded or have a circuit breaker B)Is the largest wire in that circuit C)Should not have a voltage to ground My notes: On the main panel, neutral is connected to the bar that is bonded with the panel, the green grounding wire is also connected to the same bar. (so does that mean the answer is A?) In the sub panel, the neutral wire is connected to the neutral bar which is isolated from the metal box with plastic between them, the Green grounding wire is separated and is connected to its own bar that is bonded to the sub panel box. In the circuit that this question applies to, --------- “The neutral wire is going to be sized larger than the Green grounding wire” (But that doesn’t mean it’s the LARGEST in the circuit right? Because the two hot wire could be the same size) --------"The neutral should have no potential difference(voltage) to the ground" (does that mean the answer is C?) (But that doesn’t mean it’s the LARGEST in the circuit right? Because the two hot wire could be the same size)

I have a chart that shows what Mike is talking about resistance or impedance of the earth depending upon the soil. moist soil (swampy like conditions) has the least resistance; as soil temperatures increase, resistance or impedance decrease; as soil temperatures decrease, resistance decreases. Dry soil offers more resistance and moist soil offers less resistance. At 68 degrees F, the chart shows 7,200 ohm-centimeters; at 23 F, it's 79,000 ohm-centimeters; at 14 F, 330,000 ohm-centimeters. Depending on the soil type: rocky, sandy, clay, shale, all effect the resistance of the ground in relation to grounding electrodes. This is a study done by ABB, who offer grounding and bonding products. They have charts that will show the different soil types and the resistance that you can expect for the type of soil in the area where you have to drive a ground rod or where you. Anyone can look them up and find the same charts.

@MikeHoltNEC

2 жыл бұрын

What value do you think this document serves?

@comingtofull-ageinchrist6736

2 жыл бұрын

@@MikeHoltNEC for one, whether I need to drive that supplemental ground rod for a service if my resistance is more that 25ohms. I think that it helps to serve what to expect on soil resistance for the grounding of a service disconnect. Most new homes have steel in the slab extended up to connect the service to ground, so it won't matter in a lot of cases. You mentioned the topic in your video, so I was offering a reference for what you said mostly, Mike, so that what you said had some kind of data to back it up, so I really offered it to support your comment. Because it was data that I had saved, and ABB is a reputable supply company, so I used it to give support to your comment.

@MikeHoltNEC

2 жыл бұрын

@@comingtofull-ageinchrist6736 I understand, thank you for helping me help others!

Where I have worked the normal transmission voltage is 13.8 kv.

We transmit at 765kV maximum here in SA

Sorry at 19.50 you start talking about water pipe. You are doing a great job.

I found this interesting but I know I was not the target audience. For some reason I cannot pinpoint where I feel there is missing information in this explanation. I live in the UK but I know that standards for Transmission are "international" so I believe they are the same in the US. After all the concept of electrical distribution was founded in the USA. What you describe is basically the last leg before entering commercial or domestic premises. We appear to part company in standards at that point. 100metres in my case. I believe for the medium and high voltage, etc transmission, it is distributed three phase but in the Delta arrangement, which does not have a neutral conductor. The average voltage across a balanced 3 phase system is 0 volts. High voltage transmission has an earth but no neutral so there is no progressive drop in grounding voltage across its length. The neutral appears when it is transformed from Delta to Wye and the single phases can be picked off from that point. It is regularly argued that the neutral conductors are undersized but that usually comes from the fact that they do not understand 3 phase distribution, where in theory, there is little actual neutral current. At this point we start to see terms like "impedance" (not simply resistance) and "diversity". This is also the reason why broken utility neutrals can be very difficult to locate.

@chrisbauer1925

2 жыл бұрын

I work at a power utility here in the USA, and we do indeed use grounded wye with a multipoint grounded neutral for MV 12.47 kV (line to line) distribution lines. The neutral is grounded every couple poles. 120/240V residential loads are served by center tapped single bushing single phase transformers connecting from a single 7.2 kv phase to the multigrounded neutral. The primary 7.2kV and secondary neutral center tap are bonded at the transformer, and in many cases literally the same neutral wire is shared between the primary and secondary system. This can and does result in utility neutral voltage showing up on customer grounding systems, as well as some primary neutral return current on customer ground rods and water piping systems. In the event of an open utility neutral this can result in elevated grounding system to earth voltage (NEV). There was a notable instance where a remote island fed by a single phase concentric neutral cable completely lost the neutral. The island didn't lose power because the return current was simply taking all of the ground rods on the island through back the earth to the substation on the mainland. It also resulted in customer complaints of high grounding system to earth voltages exceeding 40VAC. Needless to say an emergency repair was made by running a separate cable as the neutral to fix the stray voltage.

Those are guy wires, not guide wires.

@gregmiller-breetz3368

Ай бұрын

And a lot of them have insulators blocking the path to earth.

My take on multiple grounding points on the utility line: If the neutral is open for whatever reason upstream of a distribution transformer, and lets say the phase voltage is 13kV to ground, primary current in transformer becomes 0, voltage on neutral terminal of transformer primary winding is now 13kV to ground. If primary neutral terminal is connected to secondary (240 Volt) neutral, the neutral wire entering a house will now be at 13kV to ground.

@MikeHoltNEC

2 жыл бұрын

You my friend totally get it. Not many will understand your comment! Congratulations.

@persona250

4 ай бұрын

This would kill an awful lot of people . The primary and secondary neutrals are not connected together .

Mike does service changes in his suit.🎉

@MikeHoltNEC

7 ай бұрын

Let's make it clear, I hate wearing a suite... but I'm Mike Holt, and I'm told I have to...

When you were talking about GEC. The correct word would be he is at the same potential because the grounds are in contact with the earth the person is standing on. Now like you said if he disconnected the cable to the ground rod and he grabbed each with one hand if there was enough current flowing back on that wire to the ground rod he could die☠ because he is in series.

The whole reason why they use double bushing transformers in California is to get rid of primary load NEV. When you connect the primary loads line to line in medium voltage networks there is no need for a neutral, therefore there won't be any NEV. Medium voltage neutrals is something generally only found on the American continent. In the rest of the world where mainly 230 Volts is the standard we don't have neutrals in medium voltage networks. All medium voltage loads are line to line. The neutral is only found in the low voltage networks from the last transformer to the end consumer. So in the low voltage networks we do have NEV but it's usually very low like less than 2 Volts. Just now it's around 5 p.m. local time the NEV is ~1 Volt. Actually the best way to get rid of NEV altogether would be to have all loads line to line even in low voltage networks. The drawback is less flexibility in your low voltage network as there will only be one usable voltage which is the line to line voltage. But it would get rid of all NEV problems and the neutral would just be a dedicated ground conductor all the way to the transformer. But this requires changing all equipment and electrical circuits of consumers to withstand line to line voltage so I don't see this happening any time soon.

In some utility side failure modes, the voltage on the neutral / egc can become quite high. One utility I interned at had a concentric neutral on a single phase submarine cable fail. The island it was feeding had a lot of sand and high resistance in the ground electrodes. Suddenly the multi grounded neutral jumped to about 30-40 volts AC, based on measurements of pole grounds to remote earth. People were complaining of shocks while touching metallic objects that were grounded. In particular, customers were complaining about shocks while standing on the ground in bare feet and touching a water hose spigot. The solution was to run an additional cable as an emergency fix for the neutral, and the longer term plan was to replace the cable altogether. I do find it somewhat alarming that a single point failure can cause dangerous touch voltages that a GFCI won't even help. A similar issue happens if a service neutral fails, with up to 120V ending up on "grounded" metallic objects. It does seem like that issue could be solved by requiring over/under-voltage protection in the main service disconnect that would sense a fault condition where there was, say, 40V on one leg of a single phase service and 200V on the other.

@MikeHoltNEC

3 ай бұрын

You are 100% right! Great example

Was this made before GFI's were introduced ?

Mike, What is the behavior of subatomic particles when there is a voltage but no current? I fully understand that if there is no load there will be no current since there is no path for the circuit to close. When we use a phase tester and insert it into the phase receptacle of the electrical outlet, it turns on showing that there is electric potential at that specific point. What do you think that happens with the electrons? are the particles inside the atom polarized or charged with potential energy waiting for a path to flow? I hope you can get my point.

@MikeHoltNEC

3 жыл бұрын

Never thought of that, so I'm speachless...

@mathman0101

2 жыл бұрын

The answer relates to the physics around electromagnetic fields. You can watch Professor Walter Lewin’s (formerly at MIT) superb lectures on electricity and electromagnetic theory. The mathematics may be beyond 99 percent of licensed electricians math knowledge but if you persist you will get a lot out of it.

@carultch

2 жыл бұрын

It is arbitrary where we define voltage to equal zero, as what ultimately matters is the voltage difference between two points. In Physics, it is defined as zero, infinitely far away from the setup of charges in question, because that's what simplifies the math as much as possible. For an electrician's purpose, you define it equal to zero at ground. What voltage indicates is the energy per unit charge, that a particle has at any given point, relative to a reference location at which we define it to equal zero. It means there is a path along an electric field (due to a setup of other charges) from the point in question to the reference location, that would either on net give it energy or take energy from it, as it travels to the reference location. Whether the energy is given or taken depends on the product of the signs of the voltage and the charge travelling the path. Voltage is known as "electric potential" in physics, because it is the negative potential function of the electric field. Potential function is a term in vector calculus. You'll also see the term EMF (electromotive force) when magnetism gets involved, a nuance that accounts for the energy exchange no longer being path-independent.

@Ormaaj

2 жыл бұрын

The mobile charge carriers in a solid state conductor are described by the Fermi-Dirac distribution. Thinking about the particles is not a very useful level of abstraction for reasoning about the bulk properties of materials and low-frequency signals with very long wavelengths that electricians are mainly concerned with.

The power of the load is carried through the wires. But, insulated wires on poles can develop substantial static voltage at surprising currents. These could kill you, so the locally isolated utility circuit must be grounded. Secondly, insulators leak current. So, the local circuit must be grounded or the neutral would rise close to line voltage from leakage. Thirdly, transmission lines induce voltages in soil and ungrounded wires. Thus, the need to keep the neutral of the local circuit loop grounded. Right?

I love Mike's videos, a lot of good information, and no BS (although if I were to nit pick: sometimes the verbiage isn't 100% accurate), however I do feel insulted sometimes. I am not a licensed electrician, but I feel like most people who are, look down at everyone who is not, assuming that they don't understand anything about electricity beyond flipping a breaker, plugging something into a receptacle, or replacing a light bulb, and making fun of people who call it a "light" instead of "luminaire". There are plenty of people with engineering degrees who understand concepts of electricity, probably way beyond many master electricians, but aren't 100% familiar with the code book and its specific lingo, because they just don't use this stuff everyday. I will keep watching Mike's stuff and look for good info on his "for pros only" forum, but it hurts a little bit to realize, that this is such an elitist group that assumes no one without a license is capable of understanding any of this.

@MikeHoltNEC

2 жыл бұрын

You are 100% right, I'm sure I've taken this attitude at times. Thank you for 'calling' us/me out, I'll be more careful to be a better leader.

@yarekk

2 жыл бұрын

@@MikeHoltNEC I appreciate it. I completely understand that no one wants to be liable for any damages or injuries caused by some idiot being encouraged by saying: "this is easy folks! anyone can do this!". Electricity is dangerous, for sure, and it's best when a licensed person can do the whole job. The reality though, is that homeowners cannot always afford to hire people to do everything. If I can get a good grasp for what and how it should be done, then I can do the apprentice's or journeyman's job, and have an electrician check in with me along the way, to make sure everything is done well, and to-code. Being a scientist and an engineer, I do strive to get a better understanding of what I'm doing, and I find your videos extremely helpful for they put all that theoretical knowledge in the context of a real life situation, and make it a lot easier to understand what is meant by the articles in the code book, which is pretty darn dry. Where I often struggle isn't really with understanding the concepts, but with: "what do I need to buy at the store, so that I can do this to code?" Lots of products out there, lots of ways to skin the cat, and only some of them are proper. I wouldn't expect you to recommend any products or brands, but I think this is where a lot of "advanced DIYers" struggle. Anyways, I truly appreciate the effort that goes into these videos and they help me a lot. Thank you!

Strong possibility that this method has side effects; like during Heavy Winds during Excessive moisture the Stableization of Grounding becomes effected as power becomes interrupted until Ground water clearing to a stable dryness point. When Neutral power becomes redistributed into the power use system!

CA tends to use delta wired transformers (two bushings, primary is connected phase to phase) to avoid high NEV. Because it doesn't rain for most of the year we have a lot of really dry soil that doesn't conduct very well so it is more difficult to keep a neutral return properly at ground potential. Delta means you don't return primary voltage through the neutral at all. Unbalanced loads can cause larger voltage changes to the phases though.

@MikeHoltNEC

Жыл бұрын

I didn't realize that, that makes total sense! This explains why my experience with 'stray voltage' issues have only been on the East Coast of the US. Thank you!

@GilmerJohn

Жыл бұрын

So on rural circuits, the "distribution" is simply two conductors without any attempt to ground anything until you get to the local transformer and there it's only the secondary? You save on grounds but you have to high voltage insulate both conductors.

@brnmcc01

Жыл бұрын

@@MikeHoltNEC xenudu02 is exactly right. Also there's a lot of mountainous terrain and dry rock isn't a good conductor either. However, one advantage of using a WYE distribution system besides the unbalanced voltage problem of a Delta system, is that if there is a primary to secondary fault on a customer transformer, hopefully the small fuse to the single bushing will blow before the customers equipment blows! Also another potential problem with a delta distribution problem is what happens in a storm, if one phase drops to ground from a tree, storm damage etc, the other part of the wire downstream from the substation after the break will still have high voltage on it, backfeeding from all the other transformers that are connected to another phase to that broken wire. What they have been doing on the west coast lately and in other highly loaded rural areas, is changing the 7200 volt transformers out for single bushing 14.4kv and doubling the utility distribution voltage, or in some high growth areas, even going to 33.3 kv distribution voltage, and using 19.2 kv single bushing transformers (160:1 turns ratio). Higher voltage = less MGN current = less NEV voltage. The resistance stays the same, so the formula you gave for NEV of E = I x R, so it can be simplified to the lower the I value, the lower the E value, which makes everything safer, and avoiding the problem of Ferroresonance problems on a Delta wired MV distribution system.

Why do you have this video unlisted? It's extremely useful and has accurate information that many do not understand!

@MikeHoltNEC

2 жыл бұрын

I'm not aware that it's unlisted, but if it is, it will be listed shortly. Thanks.

hey mike we live in Thailand which has NO defined standards - and terrible awful training - I've decided on my property because it has many concrete bases with steel rebar, to weld and bond all my rebar together provide lightning paths etc, (free ions in concrete) and several connection points, in what is called a Ufer Ground (look it up now), I also provided double rcds, don't forget that computers have filter capacitors connected to the ground wire from each leg so there is always a small current or a BIG one if the capacitor fails and I've got some Ham radio gear too I want to protect it all. BUT, finally I use British MK 3 pin plugs/socktes with "kid finger proof" shutters and plugs with plastic half shafts, you should see the Thai's faces as they can't poke bare wires into my mains supplies. Anyone self building should remember that an earth rod will not be as good as a properly welded togther rebar UFER GROUNDING as the area (sq mm) and reliability (rusting etc) "earth rods" (encased in copper/steel rods) does not compare to sq meters of concrete in your ground.

So I’m welding in my garage on my small mig welder (120vac) and the utility neutral wire coming from my pole breaks and disconnects. Does my welder stop working? [I’m guessing it will still operate and hopefully my welder isn’t drawing well over the ampacity of my earthing conductor wire. ]

@persona250

4 ай бұрын

I’m not familiar with how welders work but if the welder chassis is earthed it will rise in voltage potential with a lost incoming neutral probably leading to a shock outside .

I wish you had explained the reason why those fatalities took place in relation to the video, gone over how 19v could be deadly, left off the multimeter mistake and what does an isolated screw driver jabbed into the ground have to do with your multimeter test? Was the screwdriver wire tied into your grounding system?

Some utilities don’t ground their guys on distribution. He is right though every riser pole and every transformer be it underground or overhead will have a down ground. If the pole had lightning arrestors the pole will have a down ground. Typically if it’s just a street light it’s not likely there is a down ground.

@MikeHoltNEC

6 ай бұрын

I did not know that! Thanks and Merry Christmas

Hi Mike! I am new to learning about this, but very interested. It took me a while to get it through my head the difference in the names of these types of grounds. I must have written notes 4 times before it stuck. And I think it stuck correctly finally. I am wondering if there is a reason why the EGC has to be grounded to the GEC? Should it not be sufficient that it's bonded to the neutral at main breaker panel? If there is a GEC at the transformer, then should the GEC for the house system and other remote buildings be located at the respective panels for each building to keep the NEV interference to a minimum? Buildings are 50m apart, but there is 1 building that is less than 5m from the Transformer. I was wondering if there is a way to isolate the EGC and the GEC to prevent the NEV from feeding back into the system? I would think they should be able to be isolated. Maybe I have missed something... ? Still learning! I am learning a lot form your videos and it is very much appreciated!

@MikeHoltNEC

2 жыл бұрын

NEV is 'normal' and you can't remove it without making the installation unbonded, which causes a safety hazard. Watch MikeHolt.com/Fundamentals for the answers to your other questions.

This is the capacitive effect of 2 conductors(the primary neutral and the earth) running parallel to each other and have opposing magnetic fields because the current is moving in opposite directions in them. The lower or closer you have the primary neutral conductor to the earth the greater the capacitive effect. The further away from the substation the greater the capacitive effect. The greater the capacitive effect for a given current the higher the neutral to ground voltage drop.

@MikeHoltNEC

Жыл бұрын

You are 100% correct! Thank you.

Philadelphia area. Multi point grounded system at every transformer pole. Yes, but can not OBSERVE a NEUTRAL conductor from pole to pole. Believe this is telling me the SUBSTATION is using a 3 phase 3 wire distribution system. thank you

California uses delta distribution transformers instead of wye transformers because soil moisture is low. Probably it would be a good idea in Wyoming and parts of Arizona as well.... but linemen need to be acutely aware of the difference.

About the parallel ground wiring within premise, you explained what the code requires, but why it so requires?

I honestly expected more from this video this guy knows the code well but does not have electrical theory answers i understand that theory was not the intention of the video but most of the time this guy said " I dont know" Learning electrical theory is crucial in understanding WHY something is safe or not. Following code is good but knowing WHY you are following code is what makes us all safe

Concerning the question as to whether a load on the premises is required to have primary neutral current flow: The primary in the transformer IS a load, regardless of power use on the premises..

@deang5622

Жыл бұрын

Not quite. A bit more explanation is needed. There is only power in the primary side of the transformer if there is power in the secondary side. As you connect a load up to the secondary side, the secondary delivers that power and there's a corresponding increase in power in the primary side. When there is no load connected to the secondary side, no power is present in either secondary or primary side. This is not quite 100% true. With no load connected on the secondary side, there is a small quiescent current passing through the primary coil. So there is in fact a small amount of power dissipation in the primary, but notice the use of the word quiescent. It is a small current, and no where near the magnitude of the load current which would occur when driving a load connected to the secondary.

@bretgreen5314

Жыл бұрын

@@deang5622 Agreed

cool video. very interesting. i have a question to which i cant find an answer. why do i have anywhere from 2 to 4 VAC when i put one lead into the soil of a house plant and the other lead into the ground of a wall socket? i did this on two different plants.

California retained phase to phase connection far longer than most other places in the US. But they're doing it much less now. Phase to phase is prone to ferroresonance, and the tendency to ferroresonance jumps at the square of the voltage. You can get away with phase to phase below 5kV with little issue. It can be a bit of problem at 12kV (A common voltage in rural California.) At 24.9kV or 34.5kV, forget about trying a phase to phase connection unless it is all three pole disconnection (including zero fuses). Any of the developed areas of California have pretty much gone to 24.9kV and 34.5kV, and the phase to phase connection is gone. It's just not as obvious because it's all in pad mount equipment nowadays.

@mernokallat645

Жыл бұрын

Europe is the oppisite. Medium voltage lines have no neutral, it was rare even back in the 1930s. Phase to phase is the only way here.

@matthewbeasley7765

Жыл бұрын

@@mernokallat645 Not just Europe, pretty much the whole rest of the world does 3 phase delta connected primary as the standard.

@mernokallat645

Жыл бұрын

@@matthewbeasley7765 Europe also uses reactance/resonant grounding, the neutral at the substation is grounded through an inductor (Petersen coil or arc suppression coil). when a phase shorts to ground the fault current is limited around 5 A and the line can remain in operation under a single fault. The low fault current also reduces the risk of shockif someone touches the pole. Some lines have ground fault protection and will disconnect power if the wire is broken and falls on the ground. I have seen doezns of videos on youtube in US or Canada when a downed power line is arcing for several minutes on the ground before power is cut.

Greetings from Eastern Europe (Romania)! I'm struggling with this question for years: is there any way to reduce the NEV stray voltage on the consumer side? Like a super low resistance electrodes system(0.5 Ohm or so)? Or the equipotentialisation bonding is the only way to stay safe from risk of NEV electrocution in risky places

@MikeHoltNEC

2 жыл бұрын

Not much that can be done,; watch the video again, and watch MikeHolt.com/Pools.

@paulhoda133

2 жыл бұрын

Amazing! NEV is useful for measuring improper bonding. And even if NEV is elevated, a proper bonding prevents shocks due to stray voltages from NEV. Thank you!

@ebaystars

Жыл бұрын

research making your own site safty grounds by making a UFER GROUNDING SYSTEM when building a new build using concrete and rebar

The ansewer for number two, should be , for any current to flow through the body, there should be a potential difference ( some voltage) between the hand and the foot, but since the neutral is grounded, in to the earth by electrode, or pipe, or any means, your foot and the neutral would be at the same potential, so there will not be any shock, just an idea

@MikeHoltNEC

2 ай бұрын

Nope, watch the video again. Grounding does not reduce NEV voltage.

I have a question.So since commed want neutral in the meter.Do I bond the neutral in the transformer to?Or the meter socket count as 1st point of bonded neutral since is screwed into the enclosure? THANKS MIKE FOR ALL YOUR DEDICATION FOR ALL OF US HERE.GOD BLESS YOU CHEERS FROM CHICAGO

@MikeHoltNEC

2 жыл бұрын

Don't worry about what the utility does with their grounding, just comply with 250.24 for electrical services.

I think the reason you don't feel the neutral current is b/c you aren't touching a hot wire... or another part of the earth with a difference in electrical potential.

@MikeHoltNEC

2 жыл бұрын

You will feel neutral current if you are in a pool or in the water touching metal parts of electrical equipment. Watch these two videos to learn more; MikeHolt.com/Pools and MikeHolt.com/Docks.

Thanks for the videos… Our utility is a 240V 50Hz system. Came here because NEV stays between 70 to 72V. Very worrying, but is this out of acceptable range? At the meter and first building, live-neutral voltage is 244-247V. Then a second building is supplied from the same meter by underground cable that is 180m long. Live-neutral measures 237-244V. Not helping to troubleshoot is the fact that utility supplied only live circuit breaker, so I can’t safely isolate neutral & earth from utility, connect a generator or inverter system and be certain such a large NEV is not a function of a fault inside the building. Any suggestions on dealing with thus?

@MikeHoltNEC

2 жыл бұрын

My video is for the U.S. electrical system. If you like, give me a call and I'll see if I can help. Call 352.360.2620 and ask to speak with me (Mike Holtt).

Great Video! Do not assume that if electrical current flow doesn't kill you, it is fine. It is not a binary proposition. It is not a choice between death and zero effects. 19 microamps has been shown in multiple well-programmed studies to cause cancer. Long-term chronic exposure causes cumulative effects. We need utility companies to run larger neutrals or add another neutral to the existing neutral (5-wire system). This reduces NEV and current flow through humans and animals, since the neutral impedance lowers when you make the conductor larger or add a second parallel conductor. Therefore more of the current flow leaves earth connections (including humans) and gets back on the wires as it should.

@alanw356

7 ай бұрын

10mA (that's milliamps, not microamps) is a commonly published threshold current that causes electrical signals sent by the brain to be overpowered, i. e. a victim cannot let go of a wire. 19 or 20mA is another threshold current for causing breathing difficulties. Breathing gets worse up to around 100mA, but increasing it beyond that up to about 200mA will cause ventricular fibrillation of the heart - the heart muscle opens and closes randomly and uncontrollably, stressing it and causing death. All these refer to "current through the human body" and the actual problems that result vary greatly according to where and how a fault is applied to the body - and therefore what part(s) of the body the current is actually flowing through - whether a victim is put in danger of falling, etc. Therefore the best thing a person can do to keep from having any unexpected current run through their body, is to prevent their body from coming into contact with conductors carrying a high enough voltage to cause these currents to flow! Before I knew much about electricity, I was shown how to tell whether a ceiling fixture was "live" by touching two fingers of one hand to the two exposed conductors. If I got a tingle in my hand - it was live! The only problem with this shortcut, was that if my feet had a low-resistance connection to earth ground (e. g. a wet basement floor), current would instead flow from the "hot" wire in the fixture, through my body, to the floor, possibly causing the above "difficulties". Likewise there would be a problem if I used fingers from each hand such that current would flow through my chest. The reason the above "trick" did not kill me was because current flowed only through one hand from one finger to the next. Never have I heard or read that electric current flowing through a human body could cause cancer (except from the tinfoil hat crowd). I would like to see where that information came from.

Hi Mike - you are such an inspiration! Really appreciate your teaching. I am building a 6 inverter off grid system tied to utility for backup battery charging. There is a lot of confusion in the community regarding inverters that bond neutral and earth ground together when in battery mode. Some inverters like the Victron explain when to remove the NEG bond, but others like my EG4 brand do not, and claim any change will void the warranty. I am very concerned about safety as well as equipment protection. If my utility supply panel is NEG bonded and my load panel is not bonded, but tied back to my supply panel, is there any good reason the inverter should connect neutral to earth ground under any mode? Installers have mentioned significant voltage showing on earth ground. Same question applies to a gas generator where the plug ties directly into either panel, the neutral and earth grounds will provide protection back to the generator without the generator needing a NEG bond. Thank you very much for your expertise and explanations. -Jay

Is a non-contact voltage tester sufficient to test safety of equipment which should be grounded? The low range model of the Klein tester has a threshold of 12V.

@FrodoOne1

Жыл бұрын

"Is a non-contact voltage tester sufficient to test safety of equipment which should be grounded?" NO ! I am quite surprised that YOU (of all commenters) should ask this question !

Remember electricity has to travel back to the source that created it . That being said electricity takes the path of least resistance . Think about that for a second it takes the path of LEAST RESISTANCE . It doesn't take the shortest path . If someone wires something incorrectly and that something has no wire to take voltage back to the utility and it enters the ground or earth no one knows which path it will take. If you get in between the path it is taking you will become a conductor . Think of a dog on a cable run. The dog can only travel along that cable . If the dog gets free from the cable it can travel anywhere . The dog loves to bite and if you get in its path you will get bitten. Please tell us where to get a stray voltage detector or how to use a multimeter to check for stray voltage especially in rural areas where no permits are required and people constantly wire things incorrectly .

@MikeHoltNEC

Жыл бұрын

Not the path of least resistance, all paths back to the source.

Hello, have a question guys, why would I still read stray voltage inside of pool, even after I turn off the main breaker next to meter box? I turn off all power to the community building and still reading voltage inside of pool, but it is only a certain location of the pool where I’m reading voltage, in my meter it’s reading .36 volts, it tingles a person inside of that pool, any thoughts fellas?

@MikeHoltNEC

2 ай бұрын

You 'should' be reading stray voltage as you described. Please watch MikeHolt.com/Pools to learn why you have the problem and how to solve the dangerous condition.

I had a customer call me because they were getting shocked touching light fixtures and brick wall ect. With no load there was 3 - 4 NEV with a load it got as high as 58 NEV. Still trying to figure this on out.

@MikeHoltNEC

Жыл бұрын

You have an open service neutral; your 58V is NOT NEV.

Hi mike. Can you help me out understanding how to tell when a bank is delta or why and how the connections differ from each other Thanks so much

@MikeHoltNEC

2 жыл бұрын

Watch this video - kzread.info/dash/bejne/a46OvLRxfcianqg.html

is 2.4-3 NEV in the pool normal

dear mike, please make a video on how to make an effective ground fault current path in a single phase 2 wire system line-ground/neutral system. thanks

@MikeHoltNEC

2 жыл бұрын

Watch "MikeHolt.com/Fundamentals" for your video!

@ohmware2020

2 жыл бұрын

@@MikeHoltNEC thanks mike

Hey Mike: I just watched your NEV video. It was well done and informative. I am a retired Safety Consultant of 30 years and followed the OSHA regulations, the NEC Codes, etc. Toward the end of my career, and noticing how many people have died of electrocutions over the years, I began to doubt the wisdom of Grounding our electical systems, as did many Engineers around the turn of the 19th century when the theory became more of a "political foorball". It is now my belief that the grouinding decision made back then was wrong. Every time we walk outside, we are in constant contact with one leg of the system, and all we have to do to get electrcuted is touch the other leg. If the systems were not referenced to ground, we would have to touch TWO connections to get electricuted. It seems to me that that is a no-brainer. Correct me if I'm wrong. Thanks.

@michaeljoncour4903

Жыл бұрын

not an electrician but i agree, lots of dead people would also agree , single wire earth return, common in rural australia, great money saver and govt. doesn't pay for funerals,they introduced earth leakage circuit breakers, can lose your power for days until electrician finds source of leak,i live in a very wet rural area with intensive electrical system and i think non grounding is safest....many thousands dead from grounding. as far as lightning goes i think close to earth would work as lightning is a damm good jumper, i hear of lots of people with fried appliances with ''protection''...

@MikeHoltNEC

Жыл бұрын

There is a long history on do we or do we not ground...

@brnmcc01

Жыл бұрын

The problem with not grounding is voltages can and will "float" to many times higher than the desired voltage and be fine and not even noticed until the voltage rises high enough for something to 'flash over' creating a huge arc flash, and then a building fire or worse. Don't do it! Alternating current circuits are very complex, and when you have inductive supplies (your utility transformer) connecting to capacitive loads (the power lines), you can have very strange and bad things happening if something isn't grounded. Seen voltages rise to as high at 1.6kv before on a 480-208 delta-wye transfomer in a building where the secondary neutral went bad. Even the very early 110v DC distribution systems were grounded. You had 3 wires from the utility back then. A red (positive) a black (negative), and a ground wire. You connected your lighting loads to either black or red to ground, and motor loads to red and black which gave you 220 volts. That was why it was very easy to convert from that system to todays 120/240v center tapped AC system, and why we have that split phase AC system.