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    #16
    Originally posted by nickelec View Post
    I live and work in NYC keep in mind that when they say " customer" that means a single account/meter alot of buildings in the city only have one meter , so one building could have 3-400 units in it but still be considered one customer According to edison

    Sent from my SM-G965U using Tapatalk
    Kind of what I was assuming any POCO would mean when they say "customer"- how many "meters" are effected.

    Knowing what size of a transformer might supply a certain number of customers - some "customers" may average under 1kW load, others may average in MW ranges, so IMO you can't really estimate such a thing this way.
    I live for today, I'm just a day behind.

    Comment


      #17
      Originally posted by Jraef View Post
      What usually happens is that a smaller distribution transformer blows up, but the sudden loss of load on the system creates a voltage surge that other transformer tap changers cannot react to fast enough and protective relaying starts cascading to shut down more and more systems in a concentric ring around the initial failure. But they can't re-energize all at once until they know where the initial fault took place.

      So what happens when a 12.47kv distribution feeder with 2,000 smaller distribution transformers trips from a tree in the line?


      Way off. I'm stunned you would say something like this.
      Our comedian shamelessly joked about a blackout. Talk about dark humor.

      Comment


        #18
        Originally posted by gar View Post
        190715-2016 EDT

        ggunn:

        I was using the 70,000 customers to try get an estimate of the size of a single transformer to support that load. But I also don't think a single transformer was the cause. That is why I mentioned a cascading event.

        I have now done a search for the weight of a 100 MVA transformer. Found this site https://www.btbplaza.com/index.php/e...a-220-33-kv-09
        It lists a weight of 104,900 kg or at 2.2 #/kg the weight is 230,780 # or 115 tons. Huge to quickly change.

        It is possible this is the size of the transformer going to our local substation.

        .

        .



        Keep in mind the media tosses the term "transformer explosion" around to describe everything electrical to which everyone follows leading to the perception thats what actually happened.



        From Con Ed:

        https://www.coned.com/en/about-us/me...e-power-outage


        A 13.8kv feeder cable shorted out underground. It happens. Up to 16 times a year according to one official report I shall post. Normally this would trip the feeder breaker at the supply substation. Rarely do more then a few customers loose power from this type of event.

        NYC uses "networks" where if one transformer or one feeder cable fails the paralleled (meshed) interconnected 208 volt secondaries keep the power flowing.


        In this case the primary and secondary protection at the 65 st substation failed- the short circuit persisted on the 13.8kv cable.

        This caused the West 49th st substation which supplies the 65 st substation to de-energize it and Astor (Astor is connected to the same 138kv 5 feeder cables that supply 65th.

        But inadvertently 49th st also cut power to 5 other 138kv cables supplying 50th and 42nd.

        So at least 4 substations were de-energized as a result.
        Our comedian shamelessly joked about a blackout. Talk about dark humor.

        Comment


          #19
          Con Ed released a report after the Washington Heights network outage in 1999.


          The appendix lists the typical yearly medium voltage cable failures for various networks in a given year:
          Attached Files
          Our comedian shamelessly joked about a blackout. Talk about dark humor.

          Comment


            #20
            Part 2:
            Attached Files
            Our comedian shamelessly joked about a blackout. Talk about dark humor.

            Comment


              #21
              A "network" can handle the loss of any medium voltage feeder cable without customer outages, or in the case of Con Edison two feeder cables can simultaneously fail without customers loosing power.


              Here is a generic structure:







              Typical Con Ed substation and network schematic:






              Source from here:

              https://www.researchgate.net/figure/...ig16_254057380
              Our comedian shamelessly joked about a blackout. Talk about dark humor.

              Comment


                #22
                Originally posted by mbrooke View Post
                But inadvertently 49th st also cut power to 5 other 138kv cables supplying 50th and 42nd.

                So at least 4 substations were de-energized as a result.
                I was sent an oscillogram from a PQ meter at a client's data center in Pittsburgh that wanted me to evaluate a 5 cycle momentary undervoltage that they saw at ~7PM on Saturday. I don't have a 138kV transmission diagram of the Northeast, but I bet it was related. Their 23kV is derived from 138kV.
                Ron

                Comment


                  #23
                  Here is the West 49st substation. It is a bulk substation.

                  It takes in Five 345kv feeders and steps down 345kv to 138kv via 5 auto-transformers.


                  It puts out 11 138kv feeders which supply 4 local substations.


                  5 138kv feeder cables supply west 65th and Astor, 5 138kv cables supply 50th and 42nd, and one 138kv cable is a tie (interconnect) to Vernon substation over in Queens.
                  Attached Files
                  Our comedian shamelessly joked about a blackout. Talk about dark humor.

                  Comment


                    #24
                    Here is the public supporting data:







                    Page 15:

                    https://www.epa.gov/sites/production/files/2017-02/documents/colby_presentation_2017_workshop.pdf




                    Attached Files
                    Our comedian shamelessly joked about a blackout. Talk about dark humor.

                    Comment


                      #25
                      The 4 substations supplied by West 49th st:
                      Attached Files
                      Our comedian shamelessly joked about a blackout. Talk about dark humor.

                      Comment


                        #26
                        Originally posted by ron View Post
                        I was sent an oscillogram from a PQ meter at a client's data center in Pittsburgh that wanted me to evaluate a 5 cycle momentary undervoltage that they saw at ~7PM on Saturday. I don't have a 138kV transmission diagram of the Northeast, but I bet it was related. Their 23kV is derived from 138kV.
                        Thank you for sharing this! This is why I post here.

                        Could be a coincidence, could be related.

                        I can't see a 13.8kv fault pulling the voltage down all the way to Pittsburgh, but if it somehow triggered a 345kv competent to fail I could see that happening.


                        I have a feeling that a lot more happened then we are told about.

                        And considering that both primary and secondary relaying also failed at Astoria 5 month earlier leads me to think Con Ed has some profound issues and is hiding it from everyone.
                        Our comedian shamelessly joked about a blackout. Talk about dark humor.

                        Comment


                          #27
                          Originally posted by gar View Post
                          190715-2016 EDT

                          ggunn:

                          I was using the 70,000 customers to try get an estimate of the size of a single transformer to support that load. But I also don't think a single transformer was the cause. That is why I mentioned a cascading event.

                          I have now done a search for the weight of a 100 MVA transformer. Found this site https://www.btbplaza.com/index.php/e...a-220-33-kv-09
                          It lists a weight of 104,900 kg or at 2.2 #/kg the weight is 230,780 # or 115 tons. Huge to quickly change.

                          It is possible this is the size of the transformer going to our local substation.

                          .

                          .



                          Transformers- I know you were asking about them.


                          West 49th st has Five 345kv-138kv auto transformers, each rated 420 MVA.

                          There is room for two more if seven total are ever needed.

                          The substation can supply power with two of the five auto transformers out of service.

                          Ie, the station is only loaded to 1,260MVA peak. And is designed for N-2 contingency.



                          From an investment report:
                          Attached Files
                          Our comedian shamelessly joked about a blackout. Talk about dark humor.

                          Comment


                            #28
                            Originally posted by gar View Post
                            190715-2016 EDT

                            ggunn:

                            I was using the 70,000 customers to try get an estimate of the size of a single transformer to support that load. But I also don't think a single transformer was the cause. That is why I mentioned a cascading event.

                            I have now done a search for the weight of a 100 MVA transformer. Found this site https://www.btbplaza.com/index.php/e...a-220-33-kv-09
                            It lists a weight of 104,900 kg or at 2.2 #/kg the weight is 230,780 # or 115 tons. Huge to quickly change.

                            It is possible this is the size of the transformer going to our local substation.

                            .

                            .
                            The local substations:


                            1) West 50th st has Five 138kv-13.8kv transformers each 65 MVA. This station supplies the Hudson network.

                            2) Astor has Five 138kv-13.8kv transformers each rated 65MVA. This station supplies Herald Square and possibly one other network (Empire).

                            Both these stations can run with two out of five transformers out of service or two out of five 138kv supply cables out of service.

                            Ie, West 50th and Astor are each loaded to 195 MVA.


                            3) West 65th st has ten 138kv-13.8kv transformers each rated 65MVA. Five of the transformers feed one section of 13.8kv gear the other Five feed another section of 13.8kv gear.

                            Section 1 feeds the Lincoln Square network while section 2 feeds the Plaza network and Rockefeller center network.

                            Like other stations 65th is also designed for N-2. The station can work with two of the five 138kv feeds out of service or each 13.8kv section can handle the two of the five transformers out of service.


                            4) West 42nd st has ten 138kv-13.8kv transformers each rated 65MVA. Five of the ten transformers feed one 13.8kv section of gear while the other five of the ten transformers feed a second section of gear.

                            Section 1 feeds the Pennsylvania network, while section 2 feeds the Columbus Circle network and the Midtown West network. (Midtown west was a chunk taken from the Pennsylvania network to off load section #1 when section #2 was freed up from herald square network being transferred to Astor)


                            If you do the math, 3 x 65 x 6 = 1,170 MVA of 1,260 MVA.
                            Attached Files
                            Our comedian shamelessly joked about a blackout. Talk about dark humor.

                            Comment


                              #29
                              Originally posted by mbrooke View Post
                              I have a feeling that a lot more happened then we are told about.

                              And considering that both primary and secondary relaying also failed at Astoria 5 month earlier leads me to think Con Ed has some profound issues and is hiding it from everyone.
                              I attended this lecture https://events.vtools.ieee.org/m/198911 in May and they were pretty forthcoming with what happened, at least what they knew at the time. Taft was a knowledgeable speaker and other than outing the relay and communication manufacturer names that were related to the issue, he went millisecond by millisecond almost through the timeline for ~4 minutes to get to the point where an unexpected tertiary distance relay cleared the fault through a short circuit limiting reactor.
                              Ron

                              Comment


                                #30
                                Originally posted by ron View Post
                                I attended this lecture https://events.vtools.ieee.org/m/198911 in May and they were pretty forthcoming with what happened, at least what they knew at the time. Taft was a knowledgeable speaker and other than outing the relay and communication manufacturer names that were related to the issue, he went millisecond by millisecond almost through the timeline for ~4 minutes to get to the point where an unexpected tertiary distance relay cleared the fault through a short circuit limiting reactor.
                                Was lecture recorded? Is there any paper out on the event? I would give anything know.
                                Our comedian shamelessly joked about a blackout. Talk about dark humor.

                                Comment

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