Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  1. pwrengrds

    Analyzing a 3-phase fault recorded waveform from an SEL relay on a 15kV feeder breaker, when did the breaker trip, why is VB at 0V before the fault ?

    getting a raw report would be useful with higher resolution, which isn't ran though a cosine filter. It's can show more interesting details. It started as a phase to phase fault (B-C). It was likely started because, as you said, B phase was grounded, when C phase became grounded it became a BC...
  2. pwrengrds

    How to use the Variac

    I used one like that to field calculate the impedance of a very large transformer (138kV, 100 MVA or so). I was impressed with myself that I came up with the same numbers as they did in the factory, it does have it's uses.
  3. pwrengrds

    Capacitor bank neutral voltage

    The controls had some issues with cycling the cap bank, that likely caused the trip, also could be harmonics on energizing. That's separate issues which will get resolved. In this case it's in relatively steady states for pre and post faults. My question is much more basic. This isn't...
  4. pwrengrds

    Capacitor bank neutral voltage

    The fuses that blew were the A phase fuses, which caused a neutral over voltage, sensed by the SEL 487v, causing CS35-1 to open. I added a 3 line to the attachment with notes. https://files.engineering.com/getfile.aspx?folder=209d263e-f09a-44a9-90fa-7210ac625728&file=Cap_A_fuses_trip_Fox_SQ_2.pdf
  5. pwrengrds

    Capacitor bank neutral voltage

    This is a ungrounded neutral capacitor bank tied to a 34.5kV main power transformer Y grounded. All the A phase fuses blew, not sure why currently. I'm looking at the event and the neutral voltage before the event was 1.2 kV < -178, likely due to voltage imbalance. After the event, before it...
  6. pwrengrds

    Relay Service Advisory List

    The only time I have had one of them smoke was when there was a standing trip and the handle was held closed. The coils are good for about 20 seconds with full voltage before the smoke comes out. I have seen them fail because of operator holding the handle, which ends up fixing the problem for...
  7. pwrengrds

    Motor RTD Wiring

    Use 2 wires into each rtd, if it's a short run it will be less than an ohm, you could measure the lead resistance and determine a fudge factor for error and adjust trips accordingly. At least it's not a 10 ohm rtd, which would add errors faster. David
  8. pwrengrds

    Motor RTD Wiring

    Usually RTDs are 3 wire, 2 for detection of wire resistance, and the 3rd for the RTD. First check the manual to see how it should be wired. The shield is usually separate and grounded at kne end only, if 3 wire, use 3 wires. David
  9. pwrengrds

    Help understanding a GE tapchanger

    Motor inrush reduction circuit.
  10. pwrengrds

    Nuisance tripping on feeder breaker &amp; 67P1T setting (Wind plant)

    The attached file isn't valid, comtrade files require *.CFG and *.DAT files to open. It's hard to judge settings without knowing the CT ratio, but a good guess is 240/1 (1200/5). If that is true then the time over current setting setting is 1056 amps (1.8xFLA) and the Inst 2 over current is...
  11. pwrengrds

    Transformer Fan operation

    What are the best practices for settings the fan control temperatures on a 50-100 MVA, 65C rise, ONAN/ONAF/ONAF, mineral oil transformer? What temperatures should the fans be set to operate at? Usually I have seen 65C/75C or 75C/85C. We are in process of startup and the manufacture is...
  12. pwrengrds

    Single phasing delta Y transformers

    It's just a single feeder with 10 padmounts in parallel. (the series comment was a brain fart, fixed) The first padmount blew up internally, no sign of damage from the outside, we found it by a resistance check from H1A-H1B, H2A-H2B (Both were open) and H3A-H3B (shorted). H1A is incoming from...
  13. pwrengrds

    Single phasing delta Y transformers

    This is at a wind farm site where the cables are underground going to multiple padmounts connected in parallel, standard setup. The main power transformer is Wye connected on the 34.5kV side. The collector string is connected delta-Wye. We had a padmount nearest to the substation (connected...
  14. pwrengrds

    C19/C20 Power

    It depends on if you have the 15 or 20 amp version, it's just a extension cord. (from my google search) David
  15. pwrengrds

    8.4kV PT primary operated ungrounded on 13.8kV system

    This is what was installed in 2005 and operating currently. The site currently has a reoccurring ground fault (monthly??) that goes away without being able to find the ground fault. The site does trip off on ground fault (generator and utility). I'm wondering if the PT's can withstand full...
  16. pwrengrds

    PT Burden Tests

    If I wanted to check the burden, I just powered it up with a relay test set and measured it with an ammeter, same with the CT, push 5 amps and measure the voltage. Usually not that much of an issue with the newer relays.
  17. pwrengrds

    8.4kV PT primary operated ungrounded on 13.8kV system

    What is your take on the rating provided. The system is connected to a 13.8kV ungrounded system, the PT's are PTG5-1-110-842F, see attached spec sheet. The PT's are connected phase to ground, the max system voltage rating is 15.5kV. Is the PT with the primary voltage rated at 8400 volts...
  18. pwrengrds

    Can't explain sporadic reduction in output power through 175A Shunt Breaker.

    Would have been nice to see voltage across the poles instead of between them but, yes, it's a bad breaker, have very high impedance A phase contacts. David
  19. pwrengrds

    Surge Arrester Blowing

    Check to see if the grounding breaker's grounding point is actually attached to ground. I've seen a few that weren't attached. The connection is more in the center, underneath the breaker, if there is just a slot for the bus to go through it's not really a grounding breaker as configurated. If...
  20. pwrengrds

    NERC reporting requirements

    The only place I found was PRC-005-6. Countable Event – A failure of a Component requiring repair or replacement, any condition discovered during the maintenance activities in Tables 1-1 through 1-5, Table 3, Tables 4-1 through 4-3, and Table 5, which requires corrective action or a Protection...

Part and Inventory Search

Back
Top