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  1. Dannielle

    X/R Ratios and Earth Faults

    Thankyou everyone, Alehman, I have been looking through our system impedance data, the great majority of feeders with X0< X1 have oil filled cables, some are older style XLPE cables, and these are all in a geographically similar area. So this may explain why we are seeing this as a problem...
  2. Dannielle

    X/R Ratios and Earth Faults

    Thankyou Kiribanda, In our system (500kV, 330kV,132kV,33kV,66kV,11kV) we have, I would estimate, over 40% of sites with 1ph-e or 2ph-e (either Gnd or phase) having the highest fault level. I realize the ground component of the 2ph-e is not relevent to CBs but for our working earths and the...
  3. Dannielle

    X/R Ratios and Earth Faults

    I have been asked to quote X/R ratios for faults. Historically we have quoted the Z1 X/R but now I am wondering if the Z0 X/R should be quoted as well. I have also been asked for the X/R for a 2 phase to earth fault. I am concerned that Z0 X/R could be confused with the single phase to earth...
  4. Dannielle

    Calculation of fault limits for cables

    Hi, I have been trying to find a reference to help me with calculating the fault duties (limits) of various cables. I want to include the effect of conductor size and sheath type and size for various operating temperatures and cable construction. If anyone can give me a reference either on the...

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