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  • Users: salem
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  1. salem

    impedance of three winding transformer

    three winding transformer with following parameters, - 132/11/11 kV (both the 11 kV windings are loaded). - 120/60/60 MVA - YN yn0 yn0 1- what is the recommended/practical Z% between HV-LV1 , HV-LV2 , and LV1-LV2 ? to limit the short circuit to 15 kA. 2- is there is a requirement for NER for...
  2. salem

    Factor of Safety for OHL tower

    Greetings, for 33 kV OHL steel lattice tower, and for designing the structure, the working loads (for normal condition, and broken wire condition) shall be multiplied by a factor of safety (=2 for NC, and =1.5 for BWC). now incase of BWC all loadings (for intact and broken wires) shall be...
  3. salem

    OHL steel lattice tower

    for 33 kV double circuit OHL lattice steel towers, what is the criteria for selecting the back to back distance (distance between tower legs). is it related to tower height, or tower slop ?. any reference for the above.
  4. salem

    OHL lattice steel tower

    for 33 kV double circuit OHL lattice steel towers, what is the criteria for selecting the back to back distance (distance between tower legs). is it related to tower height, or tower slop ?. any reference for the above.
  5. salem

    Loading calculations on steel lattice OHL tower

    Why broken wire condition is not considered while calculating the loading on OHL steel lattice dead end/terminal tower?
  6. salem

    EMI generated from power cable

    How to calculate the electromagnetic interference generated from a 132kV single core (in trefoil formation) power cable, need to be calculated for diffrent distances, like 1m, 2m,5m.
  7. salem

    11/0.4 kV transformer neutral earthing

    1500 kVA transformer, 11/0.4 kV Dyn11 installed in a substation what is the standard or practice for earthing the LV side neutral point ? is it required that the neutral point should have a separate earthing point/system or it can be connected with the substation earthing system? what is the...
  8. salem

    Residual Current Devise (RCD)

    0n 415 V TT earthed system, Can we use Residual Current Device (RCD) at load side. I'm having a case where RCD is tripping when we supply from portable generator with unearthed neutral, but not tripping when we supply from a transformer with earthed neutral.
  9. salem

    single fuse blown

    Hi' in three phase motor circuit, is it required to replace all the three phases fuses' if one phase fuse blown ?
  10. salem

    Battery Sizing (load profile)

    For battery sizing, can we convert a load (A) for 150ms to equivalent load for 1 sec, as a percentage value e.g. 180 A for 150ms is equivalent to (150ms / 1000 ms) X 180 = 27 A for 1 sec (1000 ms) This is required as the minimum time duration which we can use in battery sizing software is 1 sec.
  11. salem

    Generator transformer vector group

    What is the recommended vector group for a generator transformer (30 MVA, 11/33 kV).?
  12. salem

    Rated short circuit current

    Is 25kA, 3sec. equal to 40kA, 1sec. ?
  13. salem

    measurement of transformer zero sequence impedance

    how to measure (test) the zero sequence impedance of two winding, three phase Dyn11 33/11 kV 15 MVA transformer?
  14. salem

    Power cable sheath test

    33 kV cable, 10 km length being laid in sections of 500 m,and in order to control the test results, for each section the cable sheath is tested and another sheath test is done after jointing each section and finally a sheath test is done for the hall cable length with joints and...
  15. salem

    Transformer zero sequence impedance compared to positive

    Is it possible that zero sequence impedance is equal to or greater than positive sequence impedance for a power transformer, whose connection is Dyn 11 33/11 kV, 15 MVA ?
  16. salem

    Transformer Diff. Tripping

    We had a case where a transformer(20 MVA) differential protection tripped under motor starting (3.3 MW motor), what could be the reason for that.the transformer was loaded at around 16 MVA at the time of motor starting.
  17. salem

    frequency during power system disturbance

    will we have the same frequency in all connected network during power system disturbances ?
  18. salem

    Autotransformer presentation

    YNad1 400/220 kV, 400MVA , Z%=12.5 autotransformer how we can present this transformer in fault calculations program where auto transformer is not available in the program library.
  19. salem

    energy meter

    an energy meter (kWhr) with the following name plate spec. Current 5000:1 A Voltage 10.5 kV/sqrt(3) : 100V/sqrt(3) is fed from voltage and current transformers with following spec. VT :10.5 kV/sqrt(3) : 110V/sqrt(3) CT :5000:1 A what will be the error in the meter reading due to voltage...
  20. salem

    Overcurrent protection versus Overload protection

    What is the difference between overcurrent protection and overload protection , can an overcurrent relay be used for protection against overload.

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