大段长高压电缆护层保护器暂态特性分析与参数优化设计

Transient Characteristic Analysis and Parameter Optimization of Sheath Protector for Large-Length High Voltage Cable

大段长高压电缆在运行时会产生过高的护层感应电压,这对电缆护层保护器的过电压防护特性提出了更高要求,因此需要针对大段长电缆护层保护器暂态特性进行分析研究。基于PSCAD仿真软件,建立了典型220 kV高压电缆线路仿真模型,得出了在短路过电压和雷击过电压情况下,高压电缆长度对护层感应电压暂态特性的影响。通过绝缘配合与能量保护相结合的方式,得到了保护器参数取值范围及电缆线路短路电流与长度的适配曲线,提出了护层保护器参数优化设计的具体方法,并进行了试验测试。测试结果表明:当电缆线路出现短路故障时,随着电缆长度的增加,护层感应电压先线性增长,随后在保护器残压阈值的限制作用下逐渐趋于"饱和"状态,现有保护器能量吸收能力难以满足大段长电缆需求;改进后的护层保护器能量吸收能力显著提升,20 k A短路电流时允许的电缆长度大幅提高,满足大段长高压电缆线路安全运行的要求。

Excessive sheath induced overvoltage occurs during the operation of large-length high voltage(HV)cables,which puts forward higher requirements for the over-voltage protection characteristics of the sheath protector. Therefore,it is necessary to analyze and study the transient characteristics of the sheath protector for large-length cables to provide a reference for the design and selection of the protector. Based on PSCAD simulation software, a typical 220 k V HV cable simulation model was established,and the influence of the cable length on the transient characteristics of the sheath induced voltage in the case of short-circuit overvoltage and lightning overvoltage was obtained. Through the combination of insulation coordination and energy protection,the parameter range of the protector and the curve of short circuit current and the cable length were obtained. The specific method for parameter optimization of the sheath protector was proposed and the test was carried out. The results show that when the short-circuit fault occurs in the cable system,the sheath induced voltage first increases linearly with increase of the cable length,and then tends to be"saturated"under the restriction of the residual voltage threshold of the protector. The energy absorption capacity of the existing sheath protector is difficult to meet the needs of large-length cables,while the energy absorption capacity of the improved sheath protector is significantly enhanced,and the allowable cable length at 20 k A short-circuit current is greatly increased to meet the requirements of safe operation of large-length HV cables. It has been verified by tests that the performance indicators of the new protector meet the requirements of GB standard.