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Converter transformer

  1. Apr 15, 2012 #1

    Something is puzzling me with the HVDC work I'm currently working with. I'm working for contracting company here in NZ contracted to complete the new HVDC converter station.

    We have 3 x single phase converter transformers on site converting the AC voltage. I was wondering why when having an input of 220kV you get 350kV DC. I believe the line windings is connected in Star and the Valve side connected in Delta.

    Can someone direct me to a link or explain to me the theory behind getting 350kVDC output? It's very intriguing from a technical point of view. We don't usually get to work on DC links here in New Zealand.

    Thank you in advance.

  2. jcsd
  3. Apr 16, 2012 #2

    jim hardy

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    i dont know for sure but would bet it has to do with the smoothing reactor.
    Reason i say that is 350/220 falls between √2 and √3 ,
    and I remember from high school that a choke input filter has better regulation.

    Here's a picture of a smoothing reactor

    and a link to Siemens - perhaps there's a tutorial there.


    page 8 of this pdf looks like a start.

    (if link doesn't work, i reached it by clicking on "HVDC Technical Compendium" here:
    http://www.energy.siemens.com/us/en/power-transmission/hvdc/hvdc-ultra/dc-components.htm [Broken])

    imteresting technology. I was never around it. Thank you Siemens for the introduction !

    old jim
    Last edited by a moderator: May 5, 2017
  4. Apr 16, 2012 #3


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    hi there

    where in Kiwiland is that being constructed? I'm an ex-pat from the Dunedin area
    350kVDC.... FAR OUT!! would love to see the rectifiers for that

    very interesting... watched that video on developments in a China network
    not my field, but enjoy learning :)

    Last edited: Apr 16, 2012
  5. Apr 16, 2012 #4
    Thanks for the replies.

    Here is my understanding so far.

    The input voltage to the converter transformer is 220kV AC, the transformer built in such a way with it's turns ratio to reduce the voltage to 143.7kV (RMS value). 143.7kVx(squar root 2) gives the voltage peak. Then you would multiple by square root 3 would give us 350kVDC output from the rectifer? Heres my question what is the meaning of square root 3? My understanding of a smoothing reactor is to reduce the harmonics in the DC output? Please correct me if I got any of the information wrong. I'm no expert just learning. Thank you for the link I'll try and comprehend what's being said. Thanks alot.

    Dave, NZ always had a 350kV dc in the south island in Benmore since the early 1990s with pole 2 (ABB technology). We are currently replacing pole 1 (270kVDC) and replacing that with SIEMENS technology to up the capacity of the power flow. New pole will be 350kVDC. It's also being built in Benmore. The valve room in Benmore is a piece of ART!!! great technology!!!
    Last edited: Apr 16, 2012
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