The Research On Electrical Design Of Offshore Substations For 400MW Offshore Wind Farm

With the development of domestic offshore wind farms,the selected sites for construction have been gradually moving into sea areas much further from the shore.Due to the larger site area and the longer transmission distance,the increase of the voltage drop and power losses on 35 kV transmission line are more obvious.Therefore,the traditional structure of offshore wind farm,an onshore substation with 35 kV submarine cables,is no longer economical and feasible.It now is a new and feasible ac power transmission scheme,which collects the power of wind turbines and raises the voltage by setting up an ac booster station at sea and then transfers the electric energy to an onshore centralized control center via AC sea cable.However,there are few achievements under construction and operation of offshore booster stations in China at present,so it is necessary to study and summarize the electrical design of offshore booster stations to form a reproducible and popularizing standardized electrical design that can ensure its safety and meet the economic feasibility of the project.In this paper,the electrical design of the offshore substation for the 400 MW offshore wind farm in Zhuanghe,Dalian,owned by China Three Gorges Corporation,which is first built in China,is studied.The paper gives the design details of its electrical primary system,the selection of the electrical equipment,the configuration of the monitoring and protection system,the configuration of the power supply system,and more.Then the paper forms a reproducible and popularizing standardized electrical design.Firstly,the selection requirements of electrical main wiring and main transformer are analyzed,and the appropriate electrical main wiring is selected by combining short-circuit current calculation.Secondly,the main parameters of the main electrical equipment are to be selected after analyzing both the results of the short circuit calculation as well as the special environmental requirement of the offshore substation.Thirdly,the monitoring and protection system for the primary system is designed in detail abide by related regulations and standards.Afterwards,according to the statistics of power consumption of the offshore booster station and relevant specifications,the complete design scheme of auxiliary power system is given,including 400 V station-service power system,UPS and DC power supply.Finally,this paper makes a conclusion of the achievements of this study and points out the future research direction.