基于ATP-EMTP的10kV配电系统不同中性点接地方式电气特性仿真分析

Simulation Analysis of Electrical Characteristics of Different Neutral Grounding Methods in 10kV Distribution System Based on ATP-EMTP

中性点接地方式的选择对10 k V配电系统的运行及故障处理具有重要作用。笔者据此详细阐述了10 kV配电系统中性点接地方式,并根据实际参数建立了10 k V配电系统中性点接地仿真模型,分析了不同方式下的电流电压特性,得出以下结论:小电阻接地的故障点电流远高于其他接地方式,且故障和非故障线路的零序电流差异较大,而小电流接地方式下的零序电流基本一致,对故障选线造成困难;小电阻接地方式下,工频过电压和弧光接地过电压约为不接地方式的82%、51%,可采用绝缘水平较低的电气设备,减少10 k V配电系统投资;对于该系统,小电阻接地优于不接地和消弧线圈接地方式。结合以上结论,笔者从继电保护配置、过电压、通信干扰以及人身安全等方面给出了小电阻值的选值:5Ω~10Ω,对该系统中性点接地方式改造有一定的工程指导意义。

The grounding mode plays an important role in the operation and fault handling of 10 kV distribution systems. Based on this,the theory of multiple neutral grounding methods for 10 kV distribution system is elaborated. The grounding simulation model of 10 kV distribution system is established according to the actual parameters. The current and voltage characteristics of different grounding modes are analyzed. We get the conclusions as follows: firstly,the fault current of the small resistance grounding is much higher than other grounding methods. And the zero sequence current difference between the fault and the non-faulty line is large,but under the small current grounding mode is basically the same,which makes the fault line selection difficult. Under the small resistance grounding mode,the power frequency overvoltage and arc grounding overvoltage are about 82% and 51% under the ungrounded mode,which is beneficial to the use of electrical equipment with lower insulation level and reduce the investment of 10 kV distribution system. Therefore,for this system,the small resistance grounding method is better than the ungrounded and arc suppression coil grounding method. Combined with the above results,the anthor gives the selection value of small resistance value from the aspects of relay protection,overvoltage,communication interference and personal safety: 5 Ω ~ 10 Ω,which has certain engineering guidance for the grounding mode modification of the system.