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Recent content by RRaghunath

  1. RRaghunath

    Ventilated Dry type transformer inside a building

    Yes, if the location in the industrial area is not too dusty. Ventilated design is always preferred as it reduces the size of transformer and hence the cost. Ventilated type is more noisy unlike the sealed ones.
  2. RRaghunath

    What is the %Z of this grounding transformer given this nameplate data ?

    The %Z value is relevant as you mentioned that the secondary Delta of the Grounding transformer is connected to an auxiliary power supply busbars. It is the %Z along with the source impedance at 15kV bus that will decide what will be the three phase fault current magnitude at 480V busbars. IEEE...
  3. RRaghunath

    35kV Line Reactors

    I don't think there is any need to equalise the tie feeder impedances. I have seen ring main networks like this before.
  4. RRaghunath

    What is the %Z of this grounding transformer given this nameplate data ?

    It seems the subject transformer is meant to be used as Grounding transformer only. Since there is no load that is going to be connected on secondary side, %Z is not relevant and hence not marked on the name plate. Zo and the expected ground fault current is relevant and has been marked.
  5. RRaghunath

    Tie Breaker in Series and Bus duct

    In such a case, when the tie is open, the respective bus incomer protection acts as back up to the outgoings of that busbar and when the two buses are tied, the incomer protection will have to act as back up to all the feeders included in Bus A & B. The tie cable or busduct will remain live from...
  6. RRaghunath

    Tie Breaker in Series and Bus duct

    Busduct or cable tie - depends on the layout. If lay out permits, bus duct is preferred for obvious reasons. Breaker at both ends or only one end - if the intent is to keep the two busses always tied / treated as a single bus, there is no need to have circuit breakers. Just one disconnector will do.
  7. RRaghunath

    Delta Winding with grounding transformer on utility sub-transmission & distribution

    Having more number of transformers with Star connected windings and neutral solidly earthed, helps reduce overall zero sequence impedance of the utility transmission system. Having a Delta on lower side insulates the utility system from L-G faults in the downstream / consumer power system.
  8. RRaghunath

    FAT : zero sequence impedance measurement test

    It is relevant only if there is source on Delta side.
  9. RRaghunath

    MCB with PT

    I suppose RYB indicators to be closest to the PT secondary terminals. Thus, the MCB or fuse comes after the indicator always. This way, in case of a fault, the healthy phase indicators continue to glow.
  10. RRaghunath

    Ground(earth) continuity conductor (ECC) within substation

    When the copper shield / armour of the HT cable is earthed at only one end, it becomes necessary to use SVLs (Surge Voltage Limiters) at the other end. The voltage rise at the unearthed end at the time of fault current flowing in the power cable (due to an external fault) will be safely...
  11. RRaghunath

    Max amount of Breakers on 34.5kv bus with no Main Circuit Breaker

    I have seen many MV stations where there used to be no Incoming breaker, the station relying on upstream breaker for any fault in the incomer as well as in the busbar, also as back up for downstream breakers. The earth fault protection (connected to transformer MV neutral CT) and other...
  12. RRaghunath

    Transient Voltage Variations for Generators - ABS requirement

    May be, the vendor needs to supply a bigger Generator (higher kVA), keeping the Prime mover same in order to meet the Voltage regulation requirement while starting the largest motor. I have seen such a thing done while sizing a Black start Generator in a Gas Turbine based Power plant.
  13. RRaghunath

    Eutectic Alloy vs E100 Solid State Overload

    Also, Bimetal overload elements could score better when it comes to corrosive places, I suppose! What is your opinion Sir!
  14. RRaghunath

    Motor Hot withstand time

    I too faced this issue and agree it becomes impractical / hugely expensive if we insist on the margins as required in the quoted specification. The numerical motor protection relays available in the market take the data that corresponds to 100% voltage at motor terminals and can calculate...
  15. RRaghunath

    223V+ on 208Y/120V 3P/4W Common?

    Yes, the voltage is high depending on when the measurement is done. During peak hours, the same could be a lower than 208 Volts. The distribution transformers in the field are not provided with any feature for on-load correction of output voltage. The nominal voltage output of the transformer...
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