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  1. Mr zezo

    Why transformer insulation resistance decrease when filled with insulating oil?

    hi ; there This question was asked by someone:"It turns out that this is normal, so what is the reason for this?" After doing the repair of the transformer, it was shipped overseas without insulating oil. Prior to that, Insulation resistance tests and Insulation Power Factor test was...
  2. Mr zezo

    LV 3 pole ACB & Neutral

    hi there ; for LV 3pole ACB (without using external ct for Neutral) 1_how the breaker calculate the Neutral current is it the vector sum of L1+L2+L3 and what will be the different of the reading of N if we connect external ct for N. 2_ for ground fault function : _what is the difference bet...
  3. Mr zezo

    Earth fault Indicator (EFI)

    sorry , sequence components are imaginary , so what do you really mean by there is no zero sequence here? do you agree with davidbeach that the 2 ph will be 180 apart so the magnetic sum will be zero! or what? thanks.
  4. Mr zezo

    Earth fault Indicator (EFI)

    that is not my question ! the fault here is open conductor not earth fault , should EFI work with open conductor fault or not? thanks.
  5. Mr zezo

    Earth fault Indicator (EFI)

    as i said up its a delta system with earthing transformer;means the 22 kv is delta and there is a nother grounding transformer used for grounding the delta system.
  6. Mr zezo

    Earth fault Indicator (EFI)

    davidbeach, why 180 ? the angle bet each phase should be 120 Not 180 shouldnot it? thanks.
  7. Mr zezo

    ungrounded star system

    delta star distribution transformer(11/.38). the neutral of the transformer star is solidly grounded, if the system is converted to ungrounded system as the neutral grounding is removed ,then what is effect of that during ph to ground fault Specially on single ph loads (220v) line to neutral for...
  8. Mr zezo

    Earth fault Indicator (EFI)

    SLD, it is nearly like that . green leds are EFI. it is open conductor fault means ampere of phases was 200A;0A;200A. thanks https://files.engineering.com/getfile.aspx?folder=f68af946-ec7d-4181-b3f7-c1b4cc65573b&file=Screenshot_20240112-025357_(1)~2.png
  9. Mr zezo

    Earth fault Indicator (EFI)

    the moral of the question is to know the way of operation of the efi device it self and its ct , meaning how it detect beacuse there was afult occurs on mv system which consits of number of kiosks and we reconnect the feeder and its ok, but there was a blown mv fuse of incoming cable , and i...
  10. Mr zezo

    Earth fault Indicator (EFI)

    thanks for your response kirbanda, but do you mean that the EFI ct will capture the zero sequence current only as in all cases the sum of the magentic field is just zero but at earth fault the sum of the magnetic field is not a zero?and hence can the EFI operates at high unbalance condition...
  11. Mr zezo

    Earth fault Indicator (EFI)

    IN (delta system) how RMU earth fault indicator operates , and what is the function of the used medium voltage cable toroid (only one toroid allaround the 3core cable), does it only measures the surrounding or the sum of magnetic field of the 3 ph or what it actually sensing? and in another...
  12. Mr zezo

    engine generator set power rating

    engine generator set power rating nameplate is KVA,KW and PF what does this mean ? what i excepect is that the generator power is rated as KVA only and i can load it with any power factor according to load type , but at any nameplate KVA,KW and PF are given , the misunderstading here is the...
  13. Mr zezo

    Transformer buchloz relay and gas bubbles

    Why gas bubbles collected in the buchholz relay and don't collect at the transformer conservative tank and goes out from the breather?and when it can escape out from the buchloz relay? (According to physics point of view.)and does the lower float affected by the gas bubbles or it just for hard...
  14. Mr zezo

    Transformer core and magnetic field

    Flux linkage which I mean is that the flux circular lines Penetrate the other coil(like, flux lines touching the other coil)as shown in attached picture, and also that's the familiar shape of circular flux lines in air , so the confusion here is in transformer core what's the shape of the flux...
  15. Mr zezo

    Transformer core and magnetic field

    that's not my question, my question is if the magnetic field passes through the core then how it linkages with the secondary windings,what I mean like jghrist said the magnetic field passes around the core not inside the core,is it true , it seems logical, IAM not taking about voltage drop here...
  16. Mr zezo

    Transformer core and magnetic field

    What about single phase transformer where primary and secondary are in different limbs!?
  17. Mr zezo

    Transformer core and magnetic field

    If primary magnetic flux is totally contained within the iron core then how the secondary winding is being linked or cut by the magnetic field without lines of force cutting the windings? specially when the primary and secondary windings are in different limbs,like single phase transformer.
  18. Mr zezo

    Medium voltage overhead transmission line capacitors discharge

    That's not my question, I know that , but if the capacitors were without built in resistors, or I just want to decrease discharging time or just want to make sure that it's completely discharged?so , what's the concept here?
  19. Mr zezo

    Transformer core grounding

    Prc , what do you mean by (During surge conditions, laminations get automatically get grounded between each other through this capacitance).how can it be,can you explain it ? And what's the main function of grounding transformer core ? I think it is to get rid of any induced voltage during...
  20. Mr zezo

    Medium voltage overhead transmission line capacitors discharge

    How can we discharge capacitors? I saw a lot of videos where they discharge medium voltage power capacitors by connecting it to ground (meaning touch each terminal lonely by grounding stick) is it true? My question here if capacitors are like batteries,so I can't just discharge a battery by...

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