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  1. oldfieldguy

    120/240V 1P-3W, 100A Service to Very Remote Building

    I used two approaches. For a metering building a thousand feed away from our nearest MCC, I chose to run single-phase 480 volts with a 480-240/120 transformer at the building. For another measurement building a mile down a pipeline right-of-way I ran a 7200 volt buried cable to a 15 kVA...
  2. oldfieldguy

    Continuous monitoring of stator insulation when the machine is offline

    Why not both? I'm 'burnt' over space heaters to maintain winding insulation integrity due to my service area being adjacent to the Gulf Of Mexico. High humidities are a constant, and the 'normal' space heaters often are not sufficient to keep windings dry. Talking our engineers into...
  3. oldfieldguy

    Auto Transfer Switch in place of Low Voltage breaker

    The ATS lacks the fault-interrupting capacity. old field guy
  4. oldfieldguy

    Terasaki AT25 breaker gunged up

    There comes a time in the life of a circuit breaker when it needs a complete tear-down and inspection, followed by reassembly using the proper lubricates. WD-40 and its numerous imitations are NOT lubricants. Our substation crews called it "PM (preventive maintenance) in a can" because if a...
  5. oldfieldguy

    6.9 kV or 13.8 kV to feed big synchronous motors?

    We had a transformer failure in a station using 6.9 kV. Search for a possible replacement or temporary rental until the original unit was repaired quickly confirmed what I suspected - 6.9 kV is NOT common. We found ONE rental, and it was less than 2/3 of the capacity we needed. Of course we...
  6. oldfieldguy

    Protective Relay Trip Circuit Monitoring

    Per your drawing: The common practice was to have a sizable resistance as part of the lamp assemble so that shorting the lamp itself or its socket would not result in a trip of the circuit breaker. I can't remember ever seeing the green light wired through the trip coil. old field guy
  7. oldfieldguy

    MV Motor Runs Uncoupled, Locked Rotor Fault When Coupled

    Had a client send a 7000HP 4160V motor in for rewind. It came back with the same symptoms you describe. Got with the rewind shop. Instead of 2300-volt windings to connect in a wye for 4160, they did 4160 windings. When hooked in a wye, those expect 7200 volts. Motor ran well when...
  8. oldfieldguy

    Advantages of Electromechanical relays over Digital relays

    davidbeach: EM relays are why modern relays have torque control equations and time dials. An SEL-411L is a device capable of may wondrous functions, but an HZ or a KD was the work of a genius. Once you have everything as numbers you can do anything that math and the available computational...
  9. oldfieldguy

    Will DC current through a window/donut type CT damage the CT in anyway?

    Older CT's used to be susceptible to magnetization due to the DC offset of starting inrush. Older electromechanical relays managed to work through the few cycles of distorted waveform before things evened back out. The CT's I experienced with this problem were part of a motor differential...
  10. oldfieldguy

    BBC: Massive Toxic Chlorine gas leak at Jordan's Aqaba port kills 13, injures hundreds !!!

    TiCl4- Mid-1980's, on graveyard shift (2300-0700). Different world back then. Actual exposure time was probably less then ten minutes. old field guy
  11. oldfieldguy

    BBC: Massive Toxic Chlorine gas leak at Jordan's Aqaba port kills 13, injures hundreds !!!

    I worked nine years in a petrochemical plant with THREE operating electrolyzer units producing chlorine and caustic soda. Small leaks were a common thing. We all carried personal escape respirators. One of those would 'load up' pretty quick in any kind of release. I got gassed a couple of...
  12. oldfieldguy

    Hoover Dam Explosion

    hokie66- You know that and I know that, but it made the news cycle. I don't think it was much of a transformer, judging from the smoke cloud. OFG old field guy
  13. oldfieldguy

    Hoover Dam Explosion

    Looks like a transformer let go. Link old field guy
  14. oldfieldguy

    Power Transformer

    What's your oscillography look like from the 387? A quick look at the transformer should give you a good idea about the 'low oil' alarms. It takes a good amount of leakage to reach 'low level'. You should see that easily. If that's the case, the question arises as to what caused that amount...
  15. oldfieldguy

    Bouncy House Safety

    Per Artisi: "Trained and licenced operaters using approved designed equipment as it is blatantly obvious by now that what is currently being used and operated is dangerous." Just exactly what we need. I can see the legislature in its "If it saves ONE child" and "We must do SOMETHING" modes...
  16. oldfieldguy

    Pole Voltage drop test on 6 pole synchronous motors

    We always did the polke drop test using a AC, the rationale being that AC might be better to detect issues with the magnetic components as well as shorted turns. old field guy
  17. oldfieldguy

    4160/120v control transformer blowing primary fuses

    When you bench-tested the transformer, did you use full voltage on the primary? Absent a full voltage test because a lot of shops don't have 4160 easily available, did you perform a reverse excitation test? In this test, using a variable voltage source and taking safety precautions because you...
  18. oldfieldguy

    Negative Power Factor

    I too would like to see vectors. In the normal world most VFD's exhibit near unity power factor, so you'd expect that when the majority of your load is on VFD, the power factor would be near unity, and when you bypass the VFD, you're back in the world of induction motors, where a power factor...
  19. oldfieldguy

    Engine RPM for continuous duty generator

    tug- The 'D-word' never crossed my mind. I thought they were all diesel. I need natural gas fueled, long legged, reliable solutions. old field guy
  20. oldfieldguy

    Engine RPM for continuous duty generator

    IBRCAN- Thanks for the response. I've found a couple of 1200-RPM units on the used/surplus/rebuilt market, but nothing has made me move towards buying one. A lot of my older stations still have original generation and those are 'big iron', heavy, slow - 750 RPM, 200 KW. Unfortunately I have...

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