The potential short-circuit current in active distribution network features time-variance with the increasing distributed generations. This feature makes the online estimation of fault level necessary. In this paper, a novel online estimation method is proposed to be implemented by either phasor measurement unit (PMU) or the measurements from protection relays. The equivalent circuit of the radial distribution network with distributed generators (DGs), e.g., wind turbines and photovoltaic cells, is derived with necessary simplifications. The natural disturbances downstream are used to evaluate the parameters of the equivalent circuit so that the potential fault level can be estimated in advance of the actual fault occurrence. A fuzzy logic identifier is presented to rank the confidence of the measurements incurred by the disturbance and to distinguish the qualified disturbance to launch the estimation. The mechanism based on multi-measurements and confidence indices was applied, to improve the accuracy. A typical distribution network in the United Kingdom (UK) with DGs was taken, as an example, to validate the proposed method under various load fluctuation. The results confirm the effectiveness of the proposed method, which is suitable for online estimation of short-circuit fault level in active distribution networks.

中文翻译：

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有源配电网短路故障等级在线估计

有源配电网中的潜在短路电流随着分布式发电量的增加而具有时变性。这一特性使得在线估计故障等级成为必要。在本文中，提出了一种新颖的在线估计方法，可以通过相量测量单元 (PMU) 或保护继电器的测量来实现。带有分布式发电机 (DG)（例如，风力涡轮机和光伏电池）的径向配电网络的等效电路是通过必要的简化推导出来的。下游的自然干扰用于评估等效电路的参数，以便在实际故障发生之前估计潜在故障级别。提出了一个模糊逻辑标识符来对干扰引起的测量的置信度进行排序，并区分合格的干扰以启动估计。应用基于多测量和置信指数的机制来提高准确性。以英国 (UK) 具有 DG 的典型配电网络为例，在各种负载波动下验证所提出的方法。结果证实了该方法的有效性，适用于有源配电网短路故障等级的在线估计。在各种负载波动下验证所提出的方法。结果证实了该方法的有效性，适用于有源配电网短路故障等级的在线估计。在各种负载波动下验证所提出的方法。结果证实了该方法的有效性，适用于有源配电网短路故障等级的在线估计。