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  • Users: haisa
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  1. haisa

    Difference between Earthing Reactor and Earthing Transformer

    Hello All. We are installing a 150MVA 330/132/33kV Y/Y/D Transformer. Is using an Earthing Transformer and Earthing Reactor together appropriate on the Tertiary winding for protection?
  2. haisa

    Short Circuit Rating

    The Short Circuit MVA level of a 132/33kv substation is 20.31pu on 100MVA base. 2 x 60MVA Transformers were installed in the substation and the two packed up within a very short time. What factors do we consider in choosing a transformer for this substation please.
  3. haisa

    MagneticBalance Test

    Hello everyone, We conducted a magnetic balance test on a 30MVA, 132/33KV transformer on all the taps at both primary and secondary. The results showed that the sum of the two voltages are different from the applied voltage by about 6V to 10V. Is this acceptable? What could be wrong please.
  4. haisa

    tan delta

    Hello Engrs We conducted a tan delta test on a 30MVA, 132/33KV transformer recently using OMICRON CPC 100. At different voltages we had values like -6%, 0.5 % and 23%. What can we deduce from these. Iread that for good insulation the value should be around 0.007% what does the minus sign imply.
  5. haisa

    Horizon Circuit Breaker

    Hello, I am please looking for a detailed wiring drawing of a Hawker Siddeley 36KV Horizon Circuit Breaker. I could not find on their website.
  6. haisa

    Power

    Hello, What are the possible faults on transmission lines apart from long trees grounding the line? We have a 330KV line that keeps tripping but continue in service once closed back. We have cleared all vegetations under the line and all terminal equipment have passed insulation resistance test...
  7. haisa

    siprotec 7ut612 differential relay

    We have wired a siprotec relay on a 60MVA, 132/33KV Transformer. All readings looks okay but the differential current is too high and the differential current on blue phase is twice the other phases. What could be the possible reasons please.
  8. haisa

    Distance relay

    Hello My distance relay at a 132/33kV terminnal sub-station is tripping due to faults on 33KV feeders. My suspicion is that it is looking at the wrong side. How do I confirm and correct this please?
  9. haisa

    Tan Delta test

    Please guide me How to conduct TAn DELTA test for power transformer.Pls give me some documents related
  10. haisa

    Transformer Rating

    Given a Transformer without nameplate, how do I find the find the Rating of the transformer at site where there is 415V?
  11. haisa

    Bucholtz Trip

    Hello Everybody We have a 30MVA, 132/33KV transformer that is tripping on bucholtz. We carried out Insulation resistance, magnitisation and short circuit tests which all shows a satisfactory result. The magnitisation and short circuit tests were carried out using 415V and the Insulation...
  12. haisa

    Earth fault protection

    I want to know the basic difference between Neutral Earth fault and Stand-by Earth fault protections please
  13. haisa

    Boiling Transformer

    We have a 30MVA, 132/33KV Transformer that was removed from service due to leakage, for about 3years and the oil was beign removed and used elsewhere. Recently, the leakages were sealed and it was filled with oil and energised without picking any load for five days. On the fifth day the primary...

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