Constant power (Scte) loads such as large induction motors or power converters in customer facilities of distribution systems have a significant effect on the fault currents and thus on the relative location of voltage sag sources. This paper evaluates the methods for determining the relative location of voltage sag sources at the point of common coupling (PCC) of Scte loads. The results of simulating 800 voltage sag events on IEEE 13 bus unbalance system (modelled by ATP) show that many of the methods fail at classifying upstream (US) faults at the PCC of Scte loads. Therefore, a new method is introduced using the ratio of current magnitudes and changes of power angle in positive sequence components, during and before the voltage sag, with a determined threshold for the currents and a specified tolerance for the power angle obtained from voltage sags generated by different fault types. The results obtained in the proposed index for similar simulation cases show that the method applied to monitors installed at the PCC of the Scte loads is very accurate. Also, the proposed index is effective for higher resistance faults and changes in the short circuit capacity (SCC) of the main grid.

中文翻译：

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配电系统中恒定功率负载的公共耦合点处的电压突降源的相对位置

配电系统用户设施中的恒定功率（Scte）负载（例如大型感应电动机或功率转换器）会对故障电流产生重大影响，从而对电压骤降源的相对位置产生重大影响。本文评估了在Scte负载的公共耦合点（PCC）处确定电压骤降源的相对位置的方法。在IEEE 13总线不平衡系统（由ATP建模）上模拟800个电压骤降事件的结果表明，许多方法无法对Scte负载PCC的上游（美国）故障进行分类。因此，在电压暂降期间和之前，使用正序分量中的电流幅度之比和功率角变化引入一种新方法，具有确定的电流阈值和从不同故障类型产生的电压骤降获得的功率角的指定公差。在拟议指标中针对类似模拟案例获得的结果表明，应用于安装在Scte负载PCC上的监视器的方法非常准确。而且，提出的指标对于较高的电阻故障和主电网的短路容量（SCC）的变化有效。