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Voltage dip caused by the sequential energization of wind turbine transformers

Voltage dip caused by the sequential energization of wind turbine transformers. I. Arana, J. Holbøll, T. Sørensen, A. H. Nielsen, O. Holmstrøm, P. Sørensen. SALES AND DISTRIBUTION. PRODUCTION. OPTIMISATION. PRIVATE CLIENTS PUBLIC CLIENTS BUSINESS CLIENTS WHOLE- SALE ENERGY EXCHANGES.

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Voltage dip caused by the sequential energization of wind turbine transformers

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  1. Voltage dip caused by the sequential energization of wind turbine transformers I. Arana, J. Holbøll, T. Sørensen, A. H. Nielsen, O. Holmstrøm, P. Sørensen

  2. SALES AND DISTRIBUTION PRODUCTION OPTIMISATION PRIVATECLIENTS PUBLIC CLIENTS BUSINESSCLIENTS WHOLE-SALE ENERGYEXCHANGES NATURAL GAS OIL RENEWABLE ENERGY COAL BIOMASS DONG ENERGY – Business Model Power

  3. DONG ENERGY – Past and future After the merger, DONG Energy is active in every link of the energy chain • Exploration and production of oil and natural gas • Generation of power at conventional power plants and renewable energy plants • Sales of electricity and gas to end consumers including energy saving consultancy services

  4. Wind power plants • Current • Nysted (132MW) • Horns Rev (64MW)  • Barrow (45 MW)  • Burbo (90 MW) • Developing • Horns Rev 2 – offshore, Denmark (209 MW)  • Gunfleet Sands I – offshore, UK (108 MW) • Gunfleet Sands II - offshore, UK (65 MW) • Walney I - offshore, UK (151 MW) • Storrun - onshore, Sweden (30 MW) • Karnice I, onshore, Poland (30MW) • London Array • On- and offshore projects in Denmark, Germany, UK, Poland, France, Sweden, and Norway • Almost 80 projects on pipeline • DONG Energy’s Social Responsibility Report 07 • By 2020, we will triple our capacity of renewable energy to approximately 3,000 MW. • 500 Wind turbines contract with Siemens Wind Power

  5. Nysted Offshore Wind Farm (2003)

  6. GPS synchronized measuring system (2007) Va, Vb, Vc Ia, Ib, Ic Va, Vb, Vc Ia, Ib, Ic Va, Vb, Vc Ia, Ib, Ic

  7. Validated transformer model from NOWF • Transformer energization measured and simulated currents at WT A09 from 15 ms to 70 ms.

  8. Overview of sequential energization of transformers

  9. Voltage phase angle switching

  10. Voltage and current at platformVzero A01 to A09 sequence

  11. Real and reactive power Vzero A01 to A09 Vzero A09 to A01

  12. Reactive power and voltage • higher Q are the ones where the energization starts in A01 • largest Vdip are the ones with peak voltage switching

  13. Sympathetic current/voltage dip Vzero A01 to A09 Vzero A09 to A01

  14. Conclusions • Validated model NOWF-> several radial energizations using PSCAD • voltage dip • switching angle • number of simultaneously energized transformers • energizing sequence direction • wind turbine transformers are switched-in independently • smallest voltage dips, and lowest inrush current • energizing direction, with 0° and 90° switching angle • starting with A09 the transformer at the far end of the cable radial • starting with A01 at the end of the cable radial closest to the wind park transformer • higher Q are the ones where the energization starts in A01 • largest Vdip are the ones with peak voltage switching • The reactive power from the previously energized transformers varies every time a transformer is energized; and it was found that this reaction depends on the relative location of the transformers • Standard transformer models PSCAD • Assess energization voltage dips against the UK P28

  15. Discussion • Sympathetic reaction from the neighboring transformer • Superimposed effects • Standard transformer model • On-going work • No generalization • Systematic study for each wind farm • Nine wind turbine transformers energized simultaneously • Not even 2% voltage dip was present. • Individual transformer energization in zero voltage switching • Lowest voltage dip of 0,26% • Voltage dips can be assessed by detailed simulation studies • Questionable if the UK P28 for voltage dips are at all relevant for wind farms given that wind turbine transformers are switched at worst a few times a year.

  16. Acknowledgment • This work is made as part of an Industrial Ph.D. project supported by the Danish Ministry of Science, Technology and Innovation, project number 08-041566. • The switching transient measurements used in this study were obtained in the project titled “Voltage conditions and transient phenomena in medium voltage grids of modern wind farms”, contract 2005-2-6345, supported by the Danish TSO Energinet.dk.

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