The looped structure of the transmission and subtransmission networks results in the bidirectional fault current passing through the protection relays. The detection of the current direction is relegated to the directional protection unit. The traditional directional overcurrent relays utilize the reference voltage phasor for the detection of the fault direction, which increases total cost due to the need for both current and voltage measurement units. In this article, a new current only directional algorithm based on the instantaneous frequency is introduced. The proposed method is robust to noise and changes in the grid parameters, such as a change in the power frequency and direction of normal power flow. To evaluate the algorithm, plenty of simulations and actual experiments are carried out in different fault conditions. Also, its performance is compared with some other directional algorithms. The results confirm that the proposed algorithm can detect fault direction with a high degree of accuracy.

中文翻译：

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定向继电器的基于瞬时频率的算法

传输和子传输网络的环形结构导致双向故障电流通过保护继电器。电流方向的检测属于方向保护单元。传统的方向过流继电器利用参考电压相量来检测故障方向，由于需要电流和电压测量单元，这增加了总成本。本文介绍了一种新的基于瞬时频率的仅电流方向算法。所提出的方法对噪声和电网参数的变化具有鲁棒性，例如电源频率和正常潮流方向的变化。为了评估算法，在不同的故障条件下进行了大量的仿真和实际实验。还，将其性能与其他一些定向算法进行比较。结果表明，所提出的算法可以高精度地检测故障方向。