基于MODELS的工频弧光接地过电压的仿真

弧光接地过电压是中性点不接地系统中危害最大的过电压之一.目前,关于弧光接地过电压的研究大都采用系统仿真,基于工频熄弧理论,通过控制开关的闭合来模拟电弧的熄灭和重燃,观察弧光接地过电压情况.由于电弧的熄灭和重燃具有强烈的统计特性,电弧不一定是在工频过零时熄灭,也不一定是在电压达到最大值时重燃.因此,按一个工频周期来设定开关的开闭时间模拟弧光接地过电压时,模型不够准确.鉴于这种情况,在对弧光接地过电压产生机理深入研究的基础上,提出了一种新的开关控制方法,采用EMTP中的控制系统暂态分析TACS模块和MODELS模块对开关的控制部分进行处理.运用MODELS模块中特定的MODELS语言编写控制程序,输出一个信号作为TACS开关的输入控制信号,当满足给定电压和电流门槛值时,开关便会相应地闭合及断开.不必按一个工频周期来设定开关的开闭时间,提高了仿真模型的精确性.将其应用于10 kV中性点不接地系统及小电阻接地系统的弧光接地过电压的研究,取得了预期效果,具有很好的应用前景.

Simulation of PF arc grounding over-voltage based on MODELS

The arc grounding voltage is one of the worst over-voltages in the non-ground neutral system. At present, system simulation is the main method about the study on the arc grounding over-voltage. Based on the power frequency (PF) arc blowout theory, arc quenching and rekindles are simulated by controlling the switch on or off to observe the situation of arc grounding over-voltage. MATLAB power system simulation toolbox and electromagnetic transient simulation software EMTP is mainly used as the simulation tool. There is a common characteristic when using the two softwares to simulate arc quenching and rekindles, the moment of switch opening and closing is set according to one power frequency period. As a matter of fact, the arc is not sure to extinguish at the moment of PF current passing zero, the arc is also not sure to rekindle at the fault phase coming to the maximum recovery voltage because of intense statistics property of arc occurring. For this reason, the simulation model based on the theory of power frequency arc-blowout theory is not accurate. In such a case, based on the intensive study on mechanism of production of arc grounding voltage, a new method is proposed in this paper. Transient analysis of control system TACS module and MODELS module of EMTP is employed to dispose of the controlling section. The controlling program is compiled by the special language of MODELS module. The output signal of MODELS module is as the input controlling signal of TACS switch. When the voltage and current meet the threshold value, the switch will be on or off correspondingly. It is not necessary to set the opening or closing time according to a power frequency cycle, simple and flexible, improving the accuracy of simulation model. When it is applied to the arc grounding over-voltage study in 10 kV non-ground neutral system and system grounded by small resistance, a good expected result is got, having a better prospect.