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    #16
    Originally posted by ramsy View Post
    There would be no comparison in cost between those public-works projects, and a home-made DIY conduit run that ignores burial depth requirements, with PVC conduit subject to the elements, or cracking in winter cold, or water intrusion.
    Of course not. Its all apples and oranges. We are getting off in the weeds a bit. We got on this because you said "5KV on poles would probably be cheaper." Maybe I am misunderstand what you were comparing against. For me, even done to code, underground would be way cheaper. I dont have the equipment to set poles, pull and tension wires, etc. I have the equipment to dig. 15 Kv primary is only low $2's a foot. Not to mention the cable route is through the woods and clearing a swath is out of the question. BTW the conduit is buried, and water doesnt matter, you know that.

    The NESC or other standard adopted at your State level, is what accident attorneys use in court to award property to injured clients. If trespassers can break that 3/4 PVC, and injure themselves, they 5-finger discount your estate. Permit violations are not necessary to prove.

    From a liability perspective, running your 2kv wire thru an electric fence with high-voltage placards may be better than ignoring duty of care to trespassers, or State level burial depth standard for 2kv in PVC. We'll be there next week, my cross-eyed cousin will work the shovels.
    I appreciate the concern, but worrying about getting sued is not even on my worry radar. IMO 2KV direct bury conductors in PVC buried 12" is safer that 15KV directly buried 36" which is what the utility would do. BTW it would be NEC compliant to install 2 KV in IMC buried 6", PVC 18" - its really not much different than LV.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

    Comment


      #17
      Originally posted by electrofelon View Post
      ..For me, even done to code, underground would be way cheaper. ..BTW it would be NEC compliant to install 2 KV in IMC buried 6", PVC 18" - its really not much different than LV.
      Is that 18" PVC depth from NEC Table 300.5, which is limited to 1kv? Arn't you at 2kv?

      Underground-cost comparisons should use utility's figure of 36" deep, thru 2400 ft of roots & rocks, before assuming its less than overhead Residential Line extension estimator.

      I stand corrected, if your equipment & labor cost can do 36" deep for less.
      Roger Ramjet NoFixNoPay

      Comment


        #18
        Originally posted by ramsy View Post
        Is that 18" PVC depth from NEC Table 300.5, which is limited to 1kv? Arn't you at 2kv?
        yes, look at table 300.50 for over 1KV. The depths arent nearly as crazy as you might think: PVC even over 40Kv is only 30". RGS/IMc is 6" regardless of the voltage.

        Underground-cost comparisons should use utility's figure of 36" deep, thru 2400 ft of roots & rocks, before assuming its less than overhead Residential Line extension estimator.

        I stand corrected, if your equipment & labor cost can do 36" deep for less.
        Again, I dont really care about comparing anything with how a utility does or would do it. I am not disputing that overhead is cheaper for utilities for multi-MW distribution lines. My line is 15KW. FWIW, IMO just the work of removing a swath of trees would be more work than digging a 36" deep trench. If I needed to bring in a few MW for some reason, probably using poles and zig zagging up the driveway would be the most economical as it would minimize tree work, even though its 50% longer.
        Ethan Brush - East West Electric. NY, WA. MA

        "You can't generalize"

        Comment


          #19
          BTW Ramsy,

          If you didnt notice I had that thread "MV on poles" a while back

          https://forums.mikeholt.com/showthread.php?t=196761

          Might be best to move the discussion over to there as that is about running non utility MV.
          Ethan Brush - East West Electric. NY, WA. MA

          "You can't generalize"

          Comment


            #20
            Originally posted by electrofelon View Post
            yes, look at table 300.50 for over 1KV. The depths arent nearly as crazy as you might think: PVC even over 40Kv is only 30". RGS/IMc is 6" regardless of the voltage..
            Roger that, NEC Tbl. 300.50, 1-22kv = 18" deep in PVC.
            I could do that below $40k, even after breaking a few ditchwhitches.
            Roger Ramjet NoFixNoPay

            Comment


              #21
              Originally posted by electrofelon View Post

              How abou that transformer picture - ever seen a #10 coming out of a load break elbow? Thats 2KV Pv wire, transformer is 2400, tapped down all the way to 2280, close enough. I was too cheap to buy custom transformers. Runs about 500 feet to where it Tees into another 1900 foot line which goes from the service pedestal and transformer to the house.

              Its good to be an electrician sometimes.
              Very cool install thanks for posting, I have contemplated doing the exact same thing many times over the years.
              Especially a step up to step down HV system on rural property. I have looked into a 1.5kV transformers and the PV wire before.
              How did you make up the stress cones? Did you actually find ones that fit?
              We run 7.2 kV underground once in a while but the local utility always makes up the stress cones. I know they have gotten easier but they can be a point of failure.
              Comments based on 2017 NEC unless otherwise noted.

              Comment


                #22
                Originally posted by tortuga View Post
                Very cool install thanks for posting, I have contemplated doing the exact same thing many times over the years.
                Especially a step up to step down HV system on rural property. I have looked into a 1.5kV transformers and the PV wire before.
                How did you make up the stress cones? Did you actually find ones that fit?
                We run 7.2 kV underground once in a while but the local utility always makes up the stress cones. I know they have gotten easier but they can be a point of failure.
                I dont think you will find a load break connector that fits such small wire. Note 310.106(A) requires minimum conductor size of #8 for 2001-5000V so that is likely why. There are two things to match up: the crimp on connector and the opening on the tail of the elbow body. Without looking real hard, I only found connectors go down to #4, but they must be available down to #8 as MV-90 #8 is a thing. The connector is a snug fit into the body of the elbow so I didnt want to deform it too much by crimping it. I guess I could have packed some more strands in there to tighten it up, but I ended up soldering it instead. The opening in the elbow only goes down to about .5 inch, but since the PV wire isnt shielded, I dont see it as being important that the cable sheath interfaces snugly with the semi-con of the elbow.

                Over 2.4KV, I would want to use shielded cables and all the correct stuff, but for <2.4, IMO its not very critical.
                Ethan Brush - East West Electric. NY, WA. MA

                "You can't generalize"

                Comment


                  #23
                  Originally posted by electrofelon View Post
                  I dont think you will find a load break connector that fits such small wire. Note 310.106(A) requires minimum conductor size of #8 for 2001-5000V so that is likely why. There are two things to match up: the crimp on connector and the opening on the tail of the elbow body. Without looking real hard, I only found connectors go down to #4, but they must be available down to #8 as MV-90 #8 is a thing. The connector is a snug fit into the body of the elbow so I didnt want to deform it too much by crimping it. I guess I could have packed some more strands in there to tighten it up, but I ended up soldering it instead. The opening in the elbow only goes down to about .5 inch, but since the PV wire isnt shielded, I dont see it as being important that the cable sheath interfaces snugly with the semi-con of the elbow.

                  Over 2.4KV, I would want to use shielded cables and all the correct stuff, but for <2.4, IMO its not very critical.
                  Gotchya, so strees-scones and the loadbreak elbows are only needed for over 2.4kV? Thats good to know. My working experience doing terminations tapers off around 600 Volts.
                  So you have 3 privately owned transformers on your property; your utility serves you regular 120/240 single phase and you have a step up transformer to 2.2kV there to feed your 1900 foot line with a transformer on the other end for your house, and you have teed into this line?
                  Comments based on 2017 NEC unless otherwise noted.

                  Comment


                    #24
                    Originally posted by tortuga View Post
                    Gotchya, so strees-scones and the loadbreak elbows are only needed for over 2.4kV? Thats good to know. My working experience doing terminations tapers off around 600 Volts.
                    It is generally accepted that you do not need shielded cables at or below 2.4KV. A few code cycles ago they did restrict non shielded cables from 4160 which was allowed, but it is still allowed for 2.4KV. I just used an elbow because that is how to interface with the pad transformer bushing. One of my transformers is a dry type and has regular mechanical lugs.


                    So you have 3 privately owned transformers on your property; your utility serves you regular 120/240 single phase and you have a step up transformer to 2.2kV there to feed your 1900 foot line with a transformer on the other end for your house, and you have teed into this line?
                    Yes. Actually the transformer at the house has two primary bushings ("loop feed") so the MV loops thru and goes to the solar. At first I was going to run 120/240 down there, but I realized the solar is getting stepped up anyway, so I might as continue the 2.2Kv down there and add another transformer since either way would be the same transformer load losses. OF course the third tranny does at no load losses but the the wire savings make it worth it.

                    IF I was going to do this for someone professionally, I would either get 2 KV transformers, or if you want to stick with regular 2.4KV, you could get 5KV airport lighting cable which is very affordable. Its very similar to the PV wire, just a little thicker.
                    Ethan Brush - East West Electric. NY, WA. MA

                    "You can't generalize"

                    Comment


                      #25
                      The HV setup on that transformer....wow...just wow.

                      Comment


                        #26
                        Originally posted by electrofelon View Post
                        It is generally accepted that you do not need shielded cables at or below 2.4KV. A few code cycles ago they did restrict non shielded cables from 4160 which was allowed, but it is still allowed for 2.4KV. I just used an elbow because that is how to interface with the pad transformer bushing. One of my transformers is a dry type and has regular mechanical lugs.




                        Yes. Actually the transformer at the house has two primary bushings ("loop feed") so the MV loops thru and goes to the solar. At first I was going to run 120/240 down there, but I realized the solar is getting stepped up anyway, so I might as continue the 2.2Kv down there and add another transformer since either way would be the same transformer load losses. OF course the third tranny does at no load losses but the the wire savings make it worth it.

                        IF I was going to do this for someone professionally, I would either get 2 KV transformers, or if you want to stick with regular 2.4KV, you could get 5KV airport lighting cable which is very affordable. Its very similar to the PV wire, just a little thicker.
                        Wow, When can we all book a tour?
                        Comments based on 2017 NEC unless otherwise noted.

                        Comment


                          #27
                          Originally posted by tortuga View Post
                          Wow, When can we all book a tour?
                          Well not until I fix this: Peter D will have a MELTDOWN if he sees it
                          Attached Files
                          Ethan Brush - East West Electric. NY, WA. MA

                          "You can't generalize"

                          Comment


                            #28
                            Originally posted by electrofelon View Post
                            Well not until I fix this: Peter D will have a MELTDOWN if he sees it
                            So you are growing your own utility poles. What's wrong with that?

                            Comment


                              #29
                              How was it to pull that 2 Kv PV wire through 1900 feet of 3/4" PVC? It looks silicone insulated so seems like a massive amount of friction for that distance.

                              Comment


                                #30
                                Originally posted by peter d View Post
                                How was it to pull that 2 Kv PV wire through 1900 feet of 3/4" PVC? It looks silicone insulated so seems like a massive amount of friction for that distance.
                                I pulled out the wire then sleeved it in 50 foot sections (Yet another code violation). Its a long walk but gets 50 feet shorter every time. Yes many MV cables are EPR rubber, but PV wire is usually just RHW-2 but it is still not great to pull. We did a bunch of 400 ish foot pulls of 8 #8's of the 2KV PV wire on a commercial PV job. It sucked, I was dreaming of SimPull.
                                Ethan Brush - East West Electric. NY, WA. MA

                                "You can't generalize"

                                Comment

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