Research On Lightning Overvoltage Of Double Circuit Transmission Lines On The Same Tower Based On MCM And EMTP

Lightning disasters are the main cause of power system failures.Lightning inrush wave overvoltage will be generated when the lightning strikes transmission lines.Even worse,if the amplitude is greater than the line lightning withstand level,the system trips and equipment failures of substation are often caused.At the same time,in order to reduce the area of transmission lines and improve the utilization rate of transmission line corridors,the doublecircuit transmission lines on the same tower has increasingly adopted by China's power grid construction.The structure of double-circuit lines on the same tower has the characteristics of high towers and multiple conductors.The traditional method of calculating lightning overvoltage is mainly based on the early single-circuit low-circuit lines.It cannot accurately evaluate the double-circuit lines on the same tower.Therefore,the research on lightning overvoltage of double-circuit transmission lines on the same tower has important practical significance.In this thesis,a substation and its 110 k V double-circuit transmission line on the same tower are used as research objects.The Monte Carlo method(MCM)and the electromagnetic transient analysis software EMTP(Electro-magnetic Transients Program)are used to study the overvoltage of lightning intrusion The line trips and substation equipment overvoltage conditions were simulated and analyzed.Its main contents are as follows:(1)First of all,according to the current research status of lightning inrush wave overvoltage,and aiming at the randomness of lightning over-voltage generated by lightning strike transmission lines,the basic idea of MCM to solve the randomness problem is introduced.At the same time,based on the EMTP simulation software,simulation calculation models for lightning,transmission lines,towers,and substation equipment are established,and preliminary work is performed for subsequent simulation calculations of lightning trip rate and overvoltage in the station.(2)Secondly,based on MCM,considering random factors such as lightning current amplitude,lightning strike location,and line superimposed power supply voltage,combined with the improved electrical geometric model,the line lightning trip rate was simulated,and the results were compared with the rules and regulations.Contrast and analyze its influencing factors.The research shows that the calculation method of the calculation method is relatively low.Compared with the traditional calculation method of the calculation method,MCM takes into account the random factors such as the lightning current amplitude and the location of the lightning strike,which is more in line with the actual lightning strike situation of the double-circuit transmission line on the same tower.Angle,grounding resistance,and tower height have a certain effect on the line lightning trip rate.(3)Then,according to the basic situation of the substation in this thesis,considering the nonlinear characteristics of the impact ground resistance,the transmission line and the substation are modeled as a whole,and the lightning overvoltage of the electrical equipment in the station are simulated and calculated under the conditions of lightning strike-back and lightning strike,respectively.And its influence factors are analyzed.The research shows that the substation operation mode,lightning strike point,tower grounding resistance,electrical distance between the arrester and the main transformer have a greater impact on the overvoltage amplitude of the substation equipment;when the inclination of the ground and the line protection angle are small,the lightning strikes on the station The equipment threat is not large,but when the angle of the two increases,the threat of lightning to the insulation level of the equipment inside the station will increase;MOA lightning arresters have better protection for the equipment inside the station.When the current flowing through the arrester is greater than the nominal at the current value,the equipment in the station will be seriously threatened.