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    Originally posted by mivey View Post
    Either be in the utility business or don't. Difficult or not, it is just part of the job.

    Seems odd to stress over NEV during a fault if you are perfectly willing to skip routine maintenance to ensure your equipment is functioning in the first place.

    Prove to me that even with functioning equipment 5 cycles of 2.4kv will not hurt someone. Calculate the body resistance, the current that will flow and check in relation to the IEC graph.



    So true. The Dilbert factor.
    Thats business I guess.

    I assume, and it proves to be true for a well-maintained system, a breaker will rarely fail when called upon, but do have backups in case.
    Not rare enough. Regardless of equipment you assume worst reasonable clearing times.


    That would work. How fast does it react and what is the trigger mechanism?

    MV breaker- it could be set so it trips in several cycles.


    Tony would know the exact details however.
    Our comedian shamelessly joked about a blackout. Talk about dark humor.

    Comment


      Originally posted by mbrooke View Post
      Prove to me that even with functioning equipment 5 cycles of 2.4kv will not hurt someone. Calculate the body resistance, the current that will flow and check in relation to the IEC graph.
      Pick whatever cycle, kV, ohm, amps you want. If you fail to maintain the equipment what have you got? Kinda defeats the purpose of worrying about all the finer details doesn't it?

      Kind of like saying you have the linemen use insulated gloves and buckets then don't test the gloves and buckets because there are too many gloves and buckets and/or they are too difficult to test.

      Originally posted by mbrooke View Post
      Not rare enough. Regardless of equipment you assume worst reasonable clearing times.
      One way to do it. Not the best way but certainly one way.

      Originally posted by mbrooke View Post
      MV breaker- it could be set so it trips in several cycles.
      Full circle?

      You were just arguing assuming the worst and that operating in several cycles was not a safe assumption. Now it is for this scheme?

      Originally posted by mbrooke View Post
      Tony would know the exact details however.
      No details for a scheme you have concluded is the answer? Sounds odd.
      BB+/BB=?

      Comment


        Originally posted by mivey View Post
        Pick whatever cycle, kV, ohm, amps you want. If you fail to maintain the equipment what have you got? Kinda defeats the purpose of worrying about all the finer details doesn't it?

        Kind of like saying you have the linemen use insulated gloves and buckets then don't test the gloves and buckets because there are too many gloves and buckets and/or they are too difficult to test.

        Page 4:

        https://www.scientificbulletin.upb.r...628_442581.pdf

        We have a voltage of 2.4kv

        5 cycles 10 cycles 15 cycles.

        Where do the values land on the physiology graph?

        One way to do it. Not the best way but certainly one way.

        Full circle?
        Yes, from fault to trip.

        Why not the best way? Voltage will not get onto the LV noodle.


        You were just arguing assuming the worst and that operating in several cycles was not a safe assumption. Now it is for this scheme?

        No details for a scheme you have concluded is the answer? Sounds odd.

        Tony would know the relaying as its not my drawing.

        But anytime you have the potential for harmful voltage on the LV neutral you isolate it from the MV noodle.
        Our comedian shamelessly joked about a blackout. Talk about dark humor.

        Comment


          Originally posted by mbrooke View Post
          Page 4:

          https://www.scientificbulletin.upb.r...628_442581.pdf

          We have a voltage of 2.4kv

          5 cycles 10 cycles 15 cycles.

          Where do the values land on the physiology graph?
          Why does it matter? You won't meet the safe area on that graph because you are counting on your protective device to not work correctly.

          Originally posted by mbrooke View Post
          Why not the best way? Voltage will not get onto the LV noodle.
          You don't know that. You don't know how that device is triggered nor how fast it reacts. Even so, you will assume the protective device is going to fail anyway.

          Originally posted by mbrooke View Post
          Tony would know the relaying as its not my drawing.

          But anytime you have the potential for harmful voltage on the LV neutral you isolate it from the MV noodle.
          That seems to be the idea but we have no details.
          BB+/BB=?

          Comment


            Originally posted by mivey View Post
            Why does it matter? You won't meet the safe area on that graph because you are counting on your protective device to not work correctly.
            Remember, I just said you can show me the results at 5 cycles. Lets first determine if 5 cycles is ok or not ok.

            You don't know that. You don't know how that device is triggered nor how fast it reacts. Even so, you will assume the protective device is going to fail anyway.
            I have always been taught to take BF into account. I normally bite my tongue, but you are going to have to tell a half dozen ISOs, NERC, FERC, and countless utilities they are doing it wrong.

            That seems to be the idea but we have no details.

            True- I'll let Tony fill us in.
            Our comedian shamelessly joked about a blackout. Talk about dark humor.

            Comment


              Originally posted by mbrooke View Post
              Remember, I just said you can show me the results at 5 cycles. Lets first determine if 5 cycles is ok or not ok.
              Let's say no for the chart that goes along with the neutral switching scheme. Now what?

              If you install the device you propose, it is a single point of failure. You claim a single point of protection is not good enough for one scheme but is good enough for another scheme.

              You can't have it both ways.

              Originally posted by mbrooke View Post
              I have always been taught to take BF into account. I normally bite my tongue, but you are going to have to tell a half dozen ISOs, NERC, FERC, and countless utilities they are doing it wrong.
              You are missing the point.

              Also, since you are name-dropping: Tell me how many of those do not maintenance their breakers because there are too many of them and/or because some of them are difficult to switch around?

              Originally posted by mbrooke View Post
              True- I'll let Tony fill us in.
              Have you contacted him?
              BB+/BB=?

              Comment


                Originally posted by mivey View Post
                Let's say no for the chart that goes along with the neutral switching scheme. Now what?
                What neutral switching scheme


                I'm asking you to use this chart on a 5 cycle clearing MGN system:









                60479-1 is the basis of what is considered safe vs unsafe and plays a role in just about every aspect of an electrical system.





                If you install the device you propose, it is a single point of failure. You claim a single point of protection is not good enough for one scheme but is good enough for another scheme.

                What device? The drawing I'm showing you has no device other then a human removable link in the underground feed version. The LV neutral is separate from the MV neutral and only a person can connect them together.


                You can't have it both ways.

                You are missing the point.

                Also, since you are name-dropping: Tell me how many of those do not maintenance their breakers because there are too many of them and/or because some of them are difficult to switch around?
                Thats my point all along. You may have small utility that has time to test every breaker on a 3 year (or the like cycle) but try being something the size ComEd, National Grid or Dominion. In such a case these guys must assume breaker failure for distribution breakers.



                Have you contacted him?

                Yup- got this reply back:


                Tony S
                Senior Member


                Join DateJul 2013LocationResting under the Major Oak UKPosts1,346Mentioned0 Post(s)Tagged0 Thread(s)

                Re: Request

                For the LV and MV earths to be linked the LV side earth nest on its own has to be <1Ω.
                Between 1Ω and a maximum of 10Ω the link is removed and the 8 metre rule comes in to play.
                >10Ω more work is needed on the earth nest to get it <10Ω.

                BTW, is there a site I can download the NEC from?

                The reports of my death are greatly exaggerated.
                Our comedian shamelessly joked about a blackout. Talk about dark humor.

                Comment


                  This being what determines the two being bonded together vs not bonded together:


                  For the LV and MV earths to be linked the LV side earth nest on its own has to be <1Ω.
                  Between 1Ω and a maximum of 10Ω the link is removed and the 8 metre rule comes in to play.
                  >10Ω more work is needed on the earth nest to get it <10Ω
                  .
                  Our comedian shamelessly joked about a blackout. Talk about dark humor.

                  Comment


                    Originally posted by mbrooke View Post
                    What neutral switching scheme
                    The switchgear you proposed as a switching scheme. You tell me.

                    Originally posted by mbrooke View Post
                    I'm asking you to use this chart on a 5 cycle clearing MGN system.
                    The clearing times are in conjunction with IEEE std 80. There we look at the corner mesh voltage to reduce exposure in and around the substation.

                    IEC may play some role in a new standard here but I haven't seen it.

                    Originally posted by mbrooke View Post
                    What device? The drawing I'm showing you has no device other then a human removable link in the underground feed version. The LV neutral is separate from the MV neutral and only a person can connect them together.
                    The device you proposed in an earlier post before you got your new information.


                    Originally posted by mbrooke View Post
                    Thats my point all along. You may have small utility that has time to test every breaker on a 3 year (or the like cycle) but try being something the size ComEd, National Grid or Dominion. In such a case these guys must assume breaker failure for distribution breakers.
                    Multi-billion dollar companies test on regular cycles as well. Been there, done that. In my experience, bigger companies tend to be better at it.

                    Just part of doing business.
                    BB+/BB=?

                    Comment


                      Originally posted by mivey View Post
                      The switchgear you proposed as a switching scheme. You tell me.

                      Not switched.

                      The MV neutral is simply not connected to the LV neutral.


                      The clearing times are in conjunction with IEEE std 80. There we look at the corner mesh voltage to reduce exposure in and around the substation.

                      IEC may play some role in a new standard here but I haven't seen it.
                      But I'm talking about a multi grounded neutral system and a user barefoot in his backyard touching a metal electric grill plugged into his exterior receptacle.



                      The device you proposed in an earlier post before you got your new information.

                      Your voltage of 2.4kv actually supports having the primary and secondary neutrals not connected.



                      Multi-billion dollar companies test on regular cycles as well. Been there, done that. In my experience, bigger companies tend to be better at it.

                      Just part of doing business.

                      Yes- but you still have 3 cycles.
                      Our comedian shamelessly joked about a blackout. Talk about dark humor.

                      Comment


                        Originally posted by mbrooke View Post
                        But I'm talking about a multi grounded neutral system and a user barefoot in his backyard touching a metal electric grill plugged into his exterior receptacle.
                        and what standard, criteria, probability tables, etc. are you using along with that scenario?

                        Originally posted by mbrooke View Post
                        Your voltage of 2.4kv actually supports having the primary and secondary neutrals not connected.
                        Could be. By what applicable standard?

                        Originally posted by mbrooke View Post
                        Yes- but you still have 3 cycles.
                        Yes. But not an assumption of failure and SOP of not testing because it is too difficult.
                        BB+/BB=?

                        Comment


                          Originally posted by mivey View Post
                          and what standard, criteria, probability tables, etc. are you using along with that scenario?

                          Could be. By what applicable standard?
                          This:





                          Yes. But not an assumption of failure and SOP of not testing because it is too difficult.


                          Even if we assume the breaker will be 100% reliable tripping under 3 cycles, the NESC does not stipulate a maximum allowable clearing time.
                          Our comedian shamelessly joked about a blackout. Talk about dark humor.

                          Comment


                            Originally posted by mbrooke View Post
                            This:


                            Even if we assume the breaker will be 100% reliable tripping under 3 cycles, the NESC does not stipulate a maximum allowable clearing time.
                            APPLICABLE standard. This IEC standard is not adopted here.

                            Nothing is perfect. Prioritize one thing and you may lessen the focus on another. Standards committees spend time debating conflicting priorities, standards, weighing statistical probabilities of things happening, etc.

                            For example: At first, secondary systems were isolated here. Tying vs. isolating was debated for quite a few years. Experts on both sides. Over time consensus decided it was safer to tie primary and secondary systems together. While it is not perfect, it was decided the benefits of tying outweighed the benefits of not tying.

                            We do have standards for neutral isolators in agricultural applications to deal with NEV. But they tie during a fault (IIRC).

                            I don't have data on the standards debate here and it appears neither do you. Until a different approach is adopted here, we live with the currently accepted standards here.
                            BB+/BB=?

                            Comment


                              Originally posted by mivey View Post
                              APPLICABLE standard. This IEC standard is not adopted here.

                              But the graph is:

                              https://www.csemag.com/articles/uls-new-gfci-classes/


                              https://www.littelfuse.com/~/media/p...whitepaper.pdf


                              UL felt it good enough to be taken seriously here using it as a foundation on which industrial GFCI protection is implemented.




                              Nothing is perfect. Prioritize one thing and you may lessen the focus on another. Standards committees spend time debating conflicting priorities, standards, weighing statistical probabilities of things happening, etc.

                              For example: At first, secondary systems were isolated here. Tying vs. isolating was debated for quite a few years. Experts on both sides. Over time consensus decided it was safer to tie primary and secondary systems together. While it is not perfect, it was decided the benefits of tying outweighed the benefits of not tying.

                              We do have standards for neutral isolators in agricultural applications to deal with NEV. But they tie during a fault (IIRC).

                              I don't have data on the standards debate here and it appears neither do you. Until a different approach is adopted here, we live with the currently accepted standards here.

                              But I am theorizing that in some cases it does more harm then good.

                              2.4kv can be brought into the structure.

                              There is nothing in the NESC which says this voltage must be cleared under 5 cycles.


                              I'd like my theory challenged and discussed because its something I'm genuinely curious about.
                              Our comedian shamelessly joked about a blackout. Talk about dark humor.

                              Comment


                                MGN

                                Originally posted by mbrooke View Post
                                Ok, say you have a 7,200 volt single phase line running down your street. A a tree falls on the primary and it comes down on the neutral conductor.


                                According to electrical theory 3,600 volts will drop across the phase conductor and 3,600 volts across the neutral going back to the substation.


                                My question is, why doesn't 3,600 volts appear on the service neutral and thus everything in the home thats grounded?
                                Simple answer is utilities, excepting California and a few others, utilize multi grounded neutral (MGN), which under the NESC requires the utility neutral to be grounded a set number of grounds per mile of neutral.

                                Then the NEC requires the structures neutral to be bonded to the structures grounding system, so in the worst case, if everything is properly grounded and bonded during a cross fault, everything rises to the same voltage level with little difference in potential, therefore making it safe and minimizing damage and hopefully pulling enough amperage to either blow a lateral cutout, or run a recloser through it's cycles and until it locks out.

                                Now that's the simple answer, in the real world there are many variables, some of which can burn a home to the ground or kill someone.

                                But luckily between the NEC and the NESC the risk is greatly minimized.

                                Wayne

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