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  1. khodges

    Hi-pot Test Voltage for new busbar added to old 11kV Board

    We have installed a 1970's vintage BVP17 type 11kV switchboard, made up of 17 CB's, manufactured by GEC (same as Reyrolle etc), and are in the process of connecting 2 new panels to the end of the board, with new 11kV busbar extensions. The original busbar was hi-pot tested at 27kV for 1 minute...
  2. khodges

    11KV Transformer Oil Change

    Settling time is partially dependant on volume ... but I assume this unit to be around 2-5,000L of oil, so a settling time of 24 hours would be sufficient. I would be wary of anything under 12 hours, as this does not allow sufficient time for oil to penetrate the kraftpaper insulation. What...
  3. khodges

    Hi-pot testing - 33kV transformer - voltage and duration?

    We have a 33kV transformer about to go for factory acceptance tests, and while this is a relatively small 300kVA unit, am unsure what voltage and duration should be used for the hi-pot test. What is recommended for such a unit? (Of note is that this unit is rated 170kV BIL). What generally...
  4. khodges

    Spelling "Misteaks"

    It's refreshing to see an interest in maintaining standards in the most basic form of engineering … namely the notation of units. You were correctly informed with regard to the units when named for the individual influential in their development ... although the official convention is for the...
  5. khodges

    Electrical Transmission Towers

    British Electricity international publish a superb series of reference books on all major aspects of the power industry from EHV transmission to powerstation DC systems. The volume you will be most interested in to answer your question is Modern Power Station Practice - EHV Transmission -...
  6. khodges

    Hydro Turbine

    As with your previous responses - send through photos - of both the turbine and casing and the external configuration of the drive shaft, and I can comment.<br><br><A HREF="mailto:kevin.hodges@genesispower.co.nz">kevin.hodges@genesispower.co.nz</A><br><br>Regards<br><br>Kevin...
  7. khodges

    Hydro Turbine

    As with your previous responses - send through photos - of both the turbine and casing and the external configuration of the drive shaft, and I can comment.<br><br>Regards<br><br>Kevin Hodges<br>Electrical Engineer<br>Genesis Power (New Zealand) Limited
  8. khodges

    One 240mm¦ or 2x120mm¦ solution ?

    To add further to the debate - The actual end application will be the determining factor, as the following must be taken into account.<br><br>1. Compare volt drop;<br><br>for 3 & 4 conductor XLPE cable<br><br>120mm2 (Cu) = 0.366mV/A.m<br>120mm2 (Al) = 0.577mV/A.m<br>240mm2 (Cu) =...
  9. khodges

    Gas Insulated High Voltage Cables and Repairs

    While Gas Insulated cables are an old technology they are used (and fortunately being replaced now) throughout the CBD of Auckland City, New Zealand.<br><br>In 1998 there was a spectacular failure of the 3 parallel 110kV cables. January 1998 was particularly hot, and soil conditions were not...
  10. khodges

    rotor bar cracks

    4.35MVA, 11kV motor is started direct on-line and has suffered from severe rotor bar cracking after about 4000 starts over 20 years. This has been repaired by a complete rebuild, but at almost 70% of the cost of a new motor.<br><br>What systems, including soft-starters and other techniques are...

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