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  1. #21
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    Default Re: neutral grounding @ pole??

    Quote Originally Posted by The Semi-Retired Electric View Post
    What I am saying is that, under normal operating circumstances, the grounding electrode system of a properly installed 120/240 volt system carries no current. The GEC should only see current upon fault conditions, lightning, or an open neutral.
    BRricher, because of unavoidable voltage drop on the neutral conductor due to un-balanced current being returned to the POCO under normal conditions, that is not true.

    If you have never had a problem with a GEC conducting current or lifting it from the grounding electrodes you have either been extremely lucky or taken measures to prevent it.

    To make that statement to an audience of DIY's or persons who are un-trained in electrical matters but may need to lift a GEC from time to time to perform a task like remove siding etc. with power on is, IMO, not very helpful.

    I started in the electrical business in 1958 ,have been responsible for design, installation and start-up on many $500M projects and have never had a problem either but I've read, studied, practiced and taught everything I can about circulating currents, NEV, loss of neutral, lightning, surges, stray voltage, step voltage, grounding & bonding and power distribution.

    I've always said grounding electrodes are a vital necessity to a complete grounding system, just as bonding, MBJ's and four wire service drops and laterals, and hate to see their role diminished.

    Good Luck from Columbiana, Alabama
    Maurice Turgeon, http://thesemi-retiredelectrician.com[/QUOTE]

    I've never recommended any such thing to any DIYs and your notion of a GEC balancing anything is just plain false unless a neutral becomes open or degraded.

  2. #22
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    Default Re: neutral grounding @ pole??

    You guys keep referring to balance. The consumer loops of our power distribution system are not now, never have been and are not intended to be a balanced system. As long as you have one line in your loop (return in this case) grounded at two or more points, it cannot be balanced.

    Balanced is defined as the supply and return lines having equal currents and equal impedances and equal capacitance to the nearest ground. A true balanced system would have slightly better loss performance, but would not be as safe as the system we employ now.

    In the early days of the electrical power industry, an electrician or utility worker had a 50% chance of an on the job fatality during their career. It was very dangerous work. So you could say that the codes are written in blood. Put your grounds in properly and live.

  3. #23
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    Default Re: neutral grounding @ pole??

    Quote Originally Posted by keith3267 View Post
    You guys keep referring to balance. The consumer loops of our power distribution system are not now, never have been and are not intended to be a balanced system. As long as you have one line in your loop (return in this case) grounded at two or more points, it cannot be balanced.

    Balanced is defined as the supply and return lines having equal currents and equal impedances and equal capacitance to the nearest ground. A true balanced system would have slightly better loss performance, but would not be as safe as the system we employ now.

    In the early days of the electrical power industry, an electrician or utility worker had a 50% chance of an on the job fatality during their career. It was very dangerous work. So you could say that the codes are written in blood. Put your grounds in properly and live.
    Keith, I never actually said the un-balanced current returning on the neutral was bad. But,it does mean due to this current flow and resultant voltage drop there is an automatic difference in the ground potential at the pole and the ground potential at a home, compared to each other. This automatically creates a step potential between the two,(albeit small) even with a properly sized and connected neutral, if the 120V loads in a home are not equal.

    The POCO could also save end users a lot of NEV grief if they did not use earth to complete the feed to us by using a four wire transmission system.

    And, by providing a 4 wire drop/lateral i.e. hot,hot,neutral & ground feed to a typical 120/240V home. Combining the neutral and ground is terrible thinking on the part of a POCO to save a buck, and is outlawed by the NEC, which the POCO is proud to proclaim they don't have to follow.

    Also, why do they skimp on the service drop (and lateral) wire sizes? I've had to shame them into using wire larger than 2/0 Al to connect to my 500 KCM CU. When usage is low the voltage is too high, when usage is high the voltage is too low.

    Good Luck from Columbiana, Alabama
    Maurice Turgeon,http://thesemi-retiredelectrician.com

  4. #24
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    Default Re: neutral grounding @ pole??

    Do I dare ask another question. Bye the way, semi- retired electric, we think alike. Its called common sense and the NEC, thanks, wayne...
    Hidden Content maintenance director...

  5. #25
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    Default Re: neutral grounding @ pole??

    "The POCO could also save end users a lot of NEV grief if they did not use earth to complete the feed to us by using a four wire transmission system."

    Earth does not complete the feed. Earth is used for safety. Attaching the neutral to earth at the electric panel serves to clamp the neutral voltage to zero as referenced to earth. If this were not done, then the neutral voltage could "float". Appliances that are plugged into the home or business distribution system do not tie ground and neutral together. The chassis of the appliance is tied to earth and the neutral is isolated. But because the neutral is grounded at the panel, the neutral is very close to zero volts and the hot is then clamped to the supply voltage above that neutral voltage. If there were no earth connections for neutral at the panel and the transformer, then the neutral voltage could float way above local (ground) zero volts and the hot would be the supply voltage above the neutral. In theory, the neutral could raise several thousand volts above local zero, imagine how dangerous that would be.

    "And, by providing a 4 wire drop/lateral i.e. hot,hot,neutral & ground feed to a typical 120/240V home. Combining the neutral and ground is terrible thinking on the part of a POCO to save a buck, and is outlawed by the NEC, which the POCO is proud to proclaim they don't have to follow."

    A fourth "earth wire" would not accomplish anything.

    "Also, why do they skimp on the service drop (and lateral) wire sizes? I've had to shame them into using wire larger than 2/0 Al to connect to my 500 KCM CU. When usage is low the voltage is too high, when usage is high the voltage is too low."

    The voltage drop due to load may be due more to the transformer size than the wire connected to it. Having said that, it does not mean that the utility is cheaping out on you. I maybe wrong here, but I sense a slight disrespect for utility engineers on your part. A utility engineer has a very difficult job. BTW, I am not a utility engineer, and I did often make fun of them when teaching classes to linemen. But I also reminded the linemen how important and difficult the engineers job is.

    The utility engineer is responsible for providing energy at the lowest cost. To do that, he/she has to consider the cost of losses against the cost of the hardware. To some extent, there are new laws for energy efficiency the utility must meet so accepting slightly higher losses for lower hardware cost where electricity is fairly cheap is no longer an option. But it still becomes a balance of losses.

    A transformer has two types of losses. The have various names but they fall into two categories, load loss and no load loss. In a commercial environment, the customer can predict the load pretty accurately and the duty cycle of that load, i.e. 8 hr x 5 days per week or 24/7. If 24/7, the transformer is usually sized about 25% larger that average load. An 8x5 would be sized pretty close to the average load.

    Residential transformers are far more difficult. The transformer is heavily loaded for a few hours a day, then lightly loaded the rest of the time. During the light load part, the no load losses become significant. The no load losses are pretty constant and do not vary much by the load. A typical residential transformer will average about 45 watts no load, and that is 45 watts 24/7.

    Load loss is exponentially dependent on the load. Under light load, they are very low, they can be less than the no load. The low voltage lines can affect the load losses significantly, especially if there is a poor connection anywhere in the circuit. As the load increases, the load losses increase at a faster rate. At rated power, the load losses can 5 to 10x the no load. At 150% rated, the load losses can be 2x what they were at rated. The utility engineer has to figure out what combination of no load and load losses will provide the least total losses over time.

    Now the voltage issue. As the load increases, the impedance of the primary winding is responsible for a percentage of the total voltage drop across the primary. If you have looked on the nameplate of a transformer, you will see a stamp indicating its %IZ. On a typical residential transformer, that will usually be between 1.5 and 3%. Lets say that it is 2% and you are on a 7200 volt circuit.

    At minimum load, the reflected impedance is so high that the primary impedance is insignificant. The reflected impedance is dropping all the primary voltage. The house would see 240v. Now the load increases to rated, say 62.5 amps. The reflected IZ has dropped to were it is 98% of the voltage drop on the primary, the primary winding IZ is 2%, which means that of the 7200 volts on the primary, 144 volts is being dropped by the primary IZ so only 7054 is available for transformation. The secondary drops to 235.2v. The higher the load, the greater the drop by the primary IZ, the less voltage available to the secondary.

    The cable size also affects the available voltage at the panel or at the appliance because of its resistance also, but unless it is really undersized or very long, I don't think it is that significant, but it is measurable.

  6. #26
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    Columbiana, Alabama
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    Default Re: neutral grounding @ pole??

    The POCO could also save end users a lot of NEV grief if they did not use earth to complete the feed to us by using a four wire transmission system."

    You haven’t responded to MEV issues but farmers have lost significant revenue due to it and are starting to win $1M lawsuits against their POCO’s as they band together.

    Earth does not complete the feed. Earth is used for safety. Attaching the neutral to earth at the electric panel serves to clamp the neutral voltage to zero as referenced to earth. If this were not done, then the neutral voltage could "float". Appliances that are plugged into the home or business distribution system do not tie ground and neutral together. The chassis of the appliance is tied to earth and the neutral is isolated. But because the neutral is grounded at the panel, the neutral is very close to zero volts and the hot is then clamped to the supply voltage above that neutral voltage. If there were no earth connections for neutral at the panel and the transformer, then the neutral voltage could float way above local (ground) zero volts and the hot would be the supply voltage above the neutral. In theory, the neutral could raise several thousand volts above local zero, imagine how dangerous that would be.

    According to the Electric Power Reasearch Institute (EPRI) as much as 60% of all power generated returns via earth.

    True, I believe that is why all the Code revisions state in 250.4 (A) (1) that earthing “will stabilize the voltage to earth during normal operations”.

    "And, by providing a 4 wire drop/lateral i.e. hot,hot,neutral & ground feed to a typical 120/240V home. Combining the neutral and ground is terrible thinking on the part of a POCO to save a buck, and is outlawed by the NEC, which the POCO is proud to proclaim they don't have to follow."

    A fourth "earth wire" would not accomplish anything.

    I was only asking for one non-current carrying ground wire. Just like we’re now required to do on farms: Changed From 2008
    •547.9(C): Revised to include branch circuits that supply buildings or structures.
    Informational Note: Methods to reduce neutral-to-earth voltages in livestock facilities include supplying buildings or structures with 4-wire single-phase services, sizing 3-wire single-phase service and feeder conductors to limit voltage drop to 2 percent, and connecting loads line-to-line.

    "Also, why do they skimp on the service drop (and lateral) wire sizes? I've had to shame them into using wire larger than 2/0 Al to connect to my 500 KCM CU. When usage is low the voltage is too high, when usage is high the voltage is too low."

    The voltage drop due to load may be due more to the transformer size than the wire connected to it. Having said that, it does not mean that the utility is cheaping out on you. I maybe wrong here, but I sense a slight disrespect for utility engineers on your part. A utility engineer has a very difficult job. BTW, I am not a utility engineer, and I did often make fun of them when teaching classes to linemen. But I also reminded the linemen how important and difficult the engineers job is.

    I don’t disrespect utility engineers, just the policies they must be forced to work with. I have a great working relationship with many of them. Some however have cost my clients large sums of money by less than full co-operation in providing specifications only after the user has committed to another set and sloppy short circuit calculations which no else can duplicate. On a new church my client was sent a $4000 bill for the first month when I had to show it was only $200. Suddenly a new CT factor was implemented.

    The utility engineer is responsible for providing energy at the lowest cost. To do that, he/she has to consider the cost of losses against the cost of the hardware. To some extent, there are new laws for energy efficiency the utility must meet so accepting slightly higher losses for lower hardware cost where electricity is fairly cheap is no longer an option. But it still becomes a balance of losses.

    A transformer has two types of losses. The have various names but they fall into two categories, load loss and no load loss. In a commercial environment, the customer can predict the load pretty accurately and the duty cycle of that load, i.e. 8 hr x 5 days per week or 24/7. If 24/7, the transformer is usually sized about 25% larger that average load. An 8x5 would be sized pretty close to the average load.

    Residential transformers are far more difficult. The transformer is heavily loaded for a few hours a day, then lightly loaded the rest of the time. During the light load part, the no load losses become significant. The no load losses are pretty constant and do not vary much by the load. A typical residential transformer will average about 45 watts no load, and that is 45 watts 24/7.

    Load loss is exponentially dependent on the load. Under light load, they are very low, they can be less than the no load. The low voltage lines can affect the load losses significantly, especially if there is a poor connection anywhere in the circuit. As the load increases, the load losses increase at a faster rate. At rated power, the load losses can 5 to 10x the no load. At 150% rated, the load losses can be 2x what they were at rated. The utility engineer has to figure out what combination of no load and load losses will provide the least total losses over time.

    Now the voltage issue. As the load increases, the impedance of the primary winding is responsible for a percentage of the total voltage drop across the primary. If you have looked on the nameplate of a transformer, you will see a stamp indicating its %IZ. On a typical residential transformer, that will usually be between 1.5 and 3%. Lets say that it is 2% and you are on a 7200 volt circuit.

    At minimum load, the reflected impedance is so high that the primary impedance is insignificant. The reflected impedance is dropping all the primary voltage. The house would see 240v. Now the load increases to rated, say 62.5 amps. The reflected IZ has dropped to were it is 98% of the voltage drop on the primary, the primary winding IZ is 2%, which means that of the 7200 volts on the primary, 144 volts is being dropped by the primary IZ so only 7054 is available for transformation. The secondary drops to 235.2v. The higher the load, the greater the drop by the primary IZ, the less voltage available to the secondary.

    The cable size also affects the available voltage at the panel or at the appliance because of its resistance also, but unless it is really undersized or very long, I don't think it is that significant, but it is measurable.

    As I stated I’ve seen 2/0 AL service drops on 400A service. The wire loss alone with only a 200A load on a 100 ft run was 6.36V Add in the transformer losses an you have a situation where servers shutdown on over voltage, light bulbs constantly need changing and motors burn up on low voltage.

    When called the first words out of the POCO are “ no problem on our end”, yet I’ve measured 256V with two different meters and everyone on the street is standing in front of their business mad as heck.

  7. #27
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    Jan 2011
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    Columbiana, Alabama
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    644

    Default Re: neutral grounding @ pole??

    Quote Originally Posted by maintenance director View Post
    Do I dare ask another question. Bye the way, semi- retired electric, we think alike. Its called common sense and the NEC, thanks, wayne...
    It was an excellent question Wayne and I knew "from the get-go" it would not be easy, but keep posting we all work for the same cause.

  8. #28
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    Dec 2007
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    Tennessee
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    Default Re: neutral grounding @ pole??

    "According to the Electric Power Reasearch Institute (EPRI) as much as 60% of all power generated returns via earth."

    I would like to see the context to this statement. I went to the ERPI website looking for a reference but could not find it. If 60% of all power generated returns via earth, then there is something wrong with that system.

    As for the farmers, I would have to see what is going on. When I ran power from my house to the well house, I used a 4 wire, but I still don't see the need for a 4 wire system from the transformer to the house.

    For your business customer, again I would have to see the set up. How big is the transformer? What is the secondary voltage? Is it a single phase or three phase service. If three phase, is it WYE or DELTA connected with a lighting tap.

    If the secondary voltage is supposed to be 240 volts and you are getting 256 in a no load, something doesn't sound right. Large voltage fluctuations in the secondary sounds like the transformer is too small.
    Last edited by keith3267; 01-11-2012 at 08:47 PM.

  9. #29
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  10. #30
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    Default Re: neutral grounding @ pole??

    Quote Originally Posted by keith3267 View Post
    <snip> Ground potential can vary from place to place, that is why you can't have too many grounds <snip>
    This exactly. Even if the power line is grounded, you shouldn't depend on that. I've never seen where too much grounding was a problem, but I've seen the ashes where the grounding was once inadequate- need I say more?

    Phil

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