Study On Reactive Power Compensation And Ampacity Calculation Of Long Distance Three-cores High Voltage Submarine Cable

Submarine cables are one of the important equipment for cross-water transmission of electricity.Reasonably configuring reactive power compensation schemes of long-distance submarine cables and accurate thermal rating of cable line is conductive to fully utilizing the present transmission lines and optimizing the future investments.The long-distance submarine cable is greatly affected by the capacitive charging current,and the reactive power compensation is usually carried out,but the reactive power compensation will change the current distribution on the line,which may cause the thermal limitation problem of the line.In addition,the metal sheath of submarine cable usually adopts the way of direct grounding at both ends,which may cause a large grounding current on the sheath and affect the ampacity of the submarine cable.In order to improve the reliability and safety of long-distance submarine cable operation,it is necessary to study the current distribution of long-distance submarine cable considering reactive power compensation and the influence of sheath current on the ampacity of submarine cable.Based on this background,reactive power compensation and ampacity calculation of long-distance submarine cables are studied in this paper.Firstly,the PI equivalent model of long-distance submarine cable line is established,and the influence of reactive power compensation in different positions on the current distribution on the line is analyzed.Based on the IEC standard,the ampacity of long-distance submarine cable line is calculated.The current distribution on the cable line with reactive power compensation and the ampacity of each section are compared and analyzed from the point of view of the whole line ampacity.The existing reactive power compensation schemes are optimized.Secondly,the inductive circulation and capacitive charging current on the metal sheath of submarine cable are calculated by analytical methods,and the current distribution on the metal sheath of submarine cable with different lengths is obtained.According to the different laying modes of submarine cable under the two working conditions of offshore wind farm and isolated island transmission,combined with the metal sheath current of the whole line.The influence of current on the temperature field and ampacity of submarine cable with different length on metal sheath is simulated and analyzed.Finally,based on the electromagnetic-thermal-current coupling simulation,the temperature field and ampacity of the submarine cable under trenchless laying method are calculated.The influence of sheath current on ampacity is analyzed,and the corresponding methods of improving ampacity is proposed.