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  1. amps21

    Finding Interturn faults in PT

    Agree with Scottf. could attempt FRA and compare standard tests, if available.
  2. amps21

    Power transformer protection with distance relays

    Thanks for your replies. I am researching more on this. I shall let know when i find out more.
  3. amps21

    Power transformer protection with distance relays

    Basically for the following, probably only one of which may not be possible with a 50/51 a. High speed protection with POTT b. Breaker Failure c. Bus backup with either reverse zone or far looking forward opmgr1, By mitigating inrush, i meant logic/ways etc. in a relay to inhibit it from...
  4. amps21

    Power transformer protection with distance relays

    Distance relays have been proposed as backup relays for transformer protection, primary protection being Differential relays. Any thoughts on 1. what zones / logic should be used. 2. Some have recommended using POTT schemes. Anybody using this? 3. Ways to mitigate inrush Thx
  5. amps21

    MOSA mounted directly on SF6 breakers

    Description : SF6 breakers are directly mounted with MOSA (station class)on the line side. The arrester neutrals are connected to the interrupter end plate (as ground). There is a gasketed joint and quite a few metallic joints before the actual ground. (the equipment is grounded and arrester is...
  6. amps21

    3.3 Kv cable grounding

    If you are talking about the conductor sheath grounding, i think: Due to varying magnetic fields there are induced voltages in the sheath and other conductors in the vicinity. Thus, The sheath should be grounded for safety reasons. There are a number of ways to ground though. Single, Both...
  7. amps21

    Surge Protection on Open Ended MV Cable

    The transformer transferred surge, initially, is cosidered being transferred thru winding capacitance rather than inductance. How much gets transferred, is completely a transformer design parameter. but like someone suggested if properly corordinated arresters are used at the high side, surge...
  8. amps21

    Static exciter - varistors

    Skogsgurra, Your explaining of energy storage in LC circuits brought my classroom days back to me. Ur teaching skills are praisable.
  9. amps21

    REF and bucholtz

    Scotty is abs. right. As u know the whole reason behind REF is to be insensitive to thru faults. I would think that this should be proven before hand by doing thru fault tests and checking current phasors @ the relay. In addition, The transformer should be tested periodically and the test...
  10. amps21

    REF and bucholtz

    I would be wrong if i meant that - gassing due to neutral CT saturation. I meant either misoperation due to NCT saturation and at the same time sudden winding stress / vibration caused by the thru fault causing the buchholz relay to operate (cause some older buchholz relays used mercury...
  11. amps21

    REF and bucholtz

    Was there any thru faults where in the NCT would saturate, it can also cause buchholz. But most likely what all the others have contributed. Winding resistance / Gas analysis ASAP
  12. amps21

    Power Transfomer Testing Instruments

    A quick point to remember: Make sure the test instruments u get use test methods and specs. etc per your relevent country standard. Also get the instruments with a cal. sticker. Google your test requirement. There are expensive test sets and economical ones too. Like AEMC, Vanguard. Visit...
  13. amps21

    Power Transfomer Testing Instruments

    Is this inhouse testing or field testing ? Routine testing or predictive maintenance testing ? I mean, please specify.
  14. amps21

    Tan Delta of 22KV to 415V transformer

    I dont think u need to apply 10kV. You can test the winding @ 1000V and then extrapolate it to 10kV. I do not think that the frequency of the test voltage can be changed. Your tester shall have test voltage @ 60Hz. Since P=V^2w.C.Tandelta, frequency will increase your insulation PF. The...
  15. amps21

    Generator exitation

    10-4, Thanks
  16. amps21

    current in 3 phase cap's

    try http://gilbertelectrical.com/library/document_library.htm
  17. amps21

    Generator exitation

    I am not very familiar with generator excitation systems but JUst a thought. Is it not possible to check the field winding resistance and check with manufacturers tested value to see if the winding is shorted or open etc.
  18. amps21

    current in 3 phase cap's

    I think although u can calculate the inrush by hand using formulaes given in IEEE 39.99-.... the most realistic switching transients can only be deciphered from EMTP modelling.
  19. amps21

    ZnO Elements in Regulating Windings of Transformers

    Obviously this is to protect from the over voltage condition in the tapwinding generated due to system transients. Delta line end tapwinding is where i used them but they may be used as deemed necessary.
  20. amps21

    ZnO Elements in Regulating Windings of Transformers

    Zno is Zinc oxide assemblies. They are used in some transformers, usually Delta connected regulating winding when the regulation is at the line end instead of the middle of delta.

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