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  1. wcarter

    The mysterious tripping during transformer's energizing

    Schneider is usually pretty good with their FSR's. Do you have the test reports from their onsite testing? If you were able to re-energize with no issues, I would look toward's the core of the trafo having become polarized (which is not unknown). This would also account for a trip on the first...
  2. wcarter

    Distorted residential power, only at night?

    st50maint, That appears to be harmonic distortion. Have you tried using your osilloscope to check for which odd harmonic it being applied into your local line?
  3. wcarter

    NEC 250.22(5)

    Slushin, Essentially, it is to limit how much current can flow to ground. If you do not have a direct return path, IE a ground connection, minimal current will flow (the amount that will is due to capacitive coupling). IE if your supply line faulted and went to ground, it will try and return to...
  4. wcarter

    Testing laboratory

    safy2004, At least in general you will need a meggar or the like for insulation resistance testing, a doble or the like for pf testing (if oil filled transformers), TTR (transformer turns ratio), a hi-pot of some sort, preferably a VLF or DC. Neta acceptance specs lay out what tests they...
  5. wcarter

    Indian Point SD

    Electricpete, I fully agree. Question for you since you seem more familiar with nuc plants than myself. I know on a decent amount of civilian plants, on HV transformers, they have installed automated DGA units that sample periodically over a set period. I'm curious to see when the last Doble...
  6. wcarter

    Multi-source Ground Fault / Modifified Differential Groud Fault

    Schneider has done as many as 8 sources, though I think more have come up recently. With 3 and 4-pole ATS's and such. What surprises me is they are the leader in MGDF cleanly. At least from what I have seen. I would think others would be in this part of the industry. Other manufacturers have...
  7. wcarter

    The mysterious tripping during transformer's energizing

    Even assuming they used pvc, vice wtr-xlpe insulation, there should not be a breakdown so soon in the cabling. With the proper grounding, the cables should not be an issue, nor should there be anything induced into or out of them. I'd perform standard transformer tests initially. Whereas I am...
  8. wcarter

    Dual voltage ratings

    My pleasure thinker. TC cable is a bit more complicated than most of us "normally" think of when dealing with cable concerns.
  9. wcarter

    Relationship between System Earthing & circuit protection

    I noticed I missed a caviat, that made you correct rbulsara. Note to self, don't attempt to think without your coffee in teh morning! The zero sequence is for three phase, four wire systems where they are supplying a three phase, three wire load. The ungrounded delta requiring a hRg, lRg, or...
  10. wcarter

    VFD break

    jraef, Thanks. I DID notice the two had a particularly simular look to them, only that this one looked nicer. I thank you for the information. I've been reading on here on and off for over a year, but finally decided to put in a few cents. So good to know. I appreciate it.
  11. wcarter

    Relationship between System Earthing & circuit protection

    rbulsara, You state this is incorrect, but the priciple is applied currently by multiple manufacturers including Siemans and Schneider Electric, with three phase, three wire systems. And I assure you, they do work. If you wish, I can find one of their drawings for this system utilizing a...
  12. wcarter

    Reactor

    Hmmm, this looks oddly like something I had to do while in school... *shrugs*
  13. wcarter

    Indian Point SD

    Probably a lighning strike or internal fault. If a lightning strike, nothing you can do. You regularly see 3-10 rapid strikes hit a transmission line prior to the protective relay/station class breaker operating. I've seen the MCOV's go with as little as 2 strikes on a 161kV line. For an...
  14. wcarter

    Potential energy savings in motors operating under partial loads

    mrspcs, The down and dirty, getting away from the technical side, from operating specs like that, you would benefit from a VFD. From what I've seen, the drives can be a bit pricey (for some people's tastes), but one example, at a carwash, they installed drives, and in three years, the drives...
  15. wcarter

    Bus Bracing for Low Voltage Switchgear

    Yes Scotty, it is VERY normal. I work for a manufacturer and you'd be surprised at how many of our customers get conflicting data. One you might love. Requirements for ground fault testing on initial installation of service entrances. It IS required in many cases, though easily over half of the...
  16. wcarter

    Power Factor Correction on Highly Variable Loads

    rawelk, Rbulsara is correct in utilizing a PFCC at the transformer. But at lower subs, IE 480V might be another option. At least one of the manufacturers has active switching on their LV PFCC's. IE, below a setpoint, it activates a 75 or 150KVAR stage to correct the pf. If this is not enough...
  17. wcarter

    VFD break

    krsh, Here is an article interview with another company than was mentioned above, but it generally covers what you asked, and has benn answered. Just a little extra support. http://www.hesya.com/html/Electric%20motors%20motor%20controls%20engineering/20080415/22506.html
  18. wcarter

    DC Drive _ Output Current

    lukin1977, I am unsure if you are looking at a specific drive, but the manual(s) for it should have the rating in it.
  19. wcarter

    Dual voltage ratings

    Thinker, This website pdf might help youy out: http://www.cable.alcan.com/NR/rdonlyres/B1A52E99-7E8E-493F-8D24-B6F8DD9E047D/0/PowerandControlTrayCableTypeTC.pdf
  20. wcarter

    Urgent Help - Circuit breaker sizing

    Beta101, Jraef is correct in the consideration in upon known loading. Also, you have to factor in available breaker sizes and rating. IE if you sized it for 9A and one is not made in that size, you would need a 10A. Also, breakers of this size are normally thermal or thermal-mag having a rating...

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