海上风电场中压电缆集电系统暂态过电压仿真

Transient Overvoltage Simulation of Medium-Voltage Cable Collector System in Offshore Wind Farm

为研究海上风电场真空断路器重燃造成机端变压器绝缘损坏的机理,特对真空断路器进行高频建模分析.首先利用自定义真空断路器模型建立了海上风电场中压电缆集电系统PSCAD/EMTDC仿真简化模型,研究了断路器重燃特性和分闸初相角以及电缆长度对机端变压器高压侧暂态过电压和重燃次数的影响.仿真结果表明:断路器3个特征参数中介质恢复强度对暂态过电压和重燃次数影响最大,分闸初相角为45°开断感性负载断路器发生重燃现象时产生的过电压最大,过电压幅值可达3.26 p.u.,陡度可达12.46 p.u..最后文中提出在机端变压器高压侧同时串联扼流线圈,并联小电容,增加氧化锌避雷器过电压保护装置.仿真结果表明加装过电压保护装置后暂态过电压幅值和陡度以及重燃总次数得到了明显的抑制.

In order to reveal the mechanism of how the re-ignition of a vacuum circuit breaker in an offshore wind farm causes the damage of the insulation of the generators with step-up transformers,the high-frequency modeling and the analysis of the vacuum circuit breaker are performed in this paper. First,a simplified simulation model of the medium-voltage cable collector system PSCAD/EMTDC for the offshore wind farms is constructed by using a self-defined vacuum circuit breaker model. Then,the effects of the re-ignition characteristics of the circuit breaker,the initial phase angle of switching and the cable length on the transient overvoltage on the high voltage( HV) side of the generators with the step-up transformers and the re-ignition number are investigated. Simulation results show that the dielectric recovery strength of the three characteristic parameters of the circuit breaker has the greatest influence on the transient overvoltage and the re-ignition number,and that,when the initial phase angle of switching is 45° and the re-ignition phenomenon caused by the interruption of an inductive load circuit breaker occurs,the overvoltage reaches the maximum and its amplitude and steepness are up to 3. 26 p. u. and 12. 46 p. u. respectively. Finally,the scheme of installing the series of choking coils,the parallel small capacitor and the overvoltage protection device of zinc oxide arrester on the HV side of the generators with the step-up transformers at the same time is proposed. Simulation results show that,after the overvoltage protection device is installed,the overvoltage amplitude and steepness as well as the re-ignition number are effectively suppressed.