Research On Lightning Overvoltage And Protection Of Compact GIS Substation

The double-circuit compact GIS substation has become a popular research topic for scholars at home and overseas which has the advantages of saving line corridors,reducing land occupation,and meeting the power demand of large loads.Different from traditional substations,compact GIS substation,which occupies a smaller area and has highly integrated equipment,is more sensitive to strong electromagnetic environments.Lightning is the most common strong electromagnetic environment in nature.Lightning overvoltage may cause damage to key equipment in substations and threaten the stable of the power system.The overvoltage of direct lightning intrusion wave,induced lightning overvoltage and the coupling overvoltage of cables in the 220kV GIS substation are separately studied in this paper.Based on ATP-EMTP,a lightning intrusion wave model for a compact GIS substation with double circuits on the same tower is established.The influencing factors of the intrusion wave are studied with the controlled variable method.The results show the tower closest to the substation has the highest intrusion wave amplitude when lightning approach,the amplitude of the wave increases linearly,the peak value of the intrusion wave shows an overall upward trend as the lightning current increasing.According to the study on the protection scheme of lightning intrusion wave in the substation,adding the lightning arrester on the incoming side of the double circuit line and the transformer side is the optimal configuration scheme.The lightning impact insulation level is 540kV.Based on the naive Bayesian network method,an early warning model of lightning intrusion wave insulation for key equipment in GIS substations was established.The lightning intrusion characteristic parameters of lightning current amplitude,lightning tower,and types of lightning strike were extracted.In the case of complete parameters,partial parameter missing and partial parameter errors,the insulation condition of key equipment in the substation is evaluated to match the simulation results,which has certain engineering guiding significance.The Bergeron model of the line is established in ATP-EMTP based on the MODELS language.The lightning electromagnetic field is approximately calculated according to the C-R formula,and the field-line coupling is calculated by the Agrawal model.The lightning induction model of the incoming line is mainly determined by the lightning current parameters,the lightning distance,and the height of the overhead line.The simulation results show that the lightning strike distance d is approximately inversely proportional to the induced lightning amplitude U,and the overhead line height h and the lightning current amplitude I are directly proportional to the induced lightning amplitude U.By using linear fitting method,the quantitative relationship of induced lightning overvoltage is obtained;a three-phase lightning arrester on the side of the incoming line of the substation is proposed to limit the amplitude of induced overvoltage on the line to 575.8kV,which is lower than the insulator flashover voltage.The protection scheme of four lightning rods in the substation is studied.The protection range is calculated by the polygon method and the rolling sphere method.It is concluded that there is a risk of direct lightning strikes on the buildings in the substation.Establish a model of lightning-struck substation building based on CST and study the coupling response of lightning electromagnetic pulse and cable to the building struck by lightning.The results show that the coupling response amplitude of indoor cables is smaller than outdoor cables,the further the horizontal cable is placed above the ground,the greater the amplitude of overvoltage.As the length of the cable increases,the amplitude of the induced overvoltage increases.This paper designs a cable induced overvoltage protection scheme:arranging the secondary system indoors can effectively reduce the line coupling response;shorten the length of the cable to ensure good transmission effects while reducing the amplitude of the induced overvoltage;the use of multi-core cables can reduce the amplitude of the induced overvoltage,reduce the number of lines,and optimize the spatial layout of substations at the same time.Using shielded cables,increasing shielding nets,and installing surge protection devices are applied for key equipment protection.