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Mal-operation of distance protection relays during power swing (PS) condition can endanger the power system stability. Therefore, it is crucial to distinguish between short-circuit faults and PS by a power swing blocking (PSB) function to prevent undesired tripping of distance relay. This paper develops a novel and straightforward PSB method based on the rate of impedance angle change (RIAC). Not only can the proposed approach fairly discriminate both symmetrical and asymmetrical faults from PS, but also it can appropriately preserve protection scheme security during PS under single-pole tripping (SPT) on a transmission line. Furthermore, there is no need to perform extensive dynamic stability studies for setting the PSB function parameters. Unlike the rate of impedance change approaches utilized two blinders, the developed approach only needs an inner blinder. Thus, it can be used for networks running near their operational limits. The proposed method is evaluated through a modified IEEE-PSRC benchmark system in PSCAD/EMTC environment. The obtained results verify superior performance of the proposed method to traditional impedance rate of change method under different scenarios. [ABSTRACT FROM AUTHOR]

This article presents a novel straightforward and real-time algorithm to measure power system frequency. The main idea of this approach is to improve accuracy of the estimated frequency during off-nominal frequency conditions. The proposed approach includes two stages: 1) the DFT algorithm is used to estimate voltage amplitude and phase angle by assuming that the frequency is the same as its value at the previous step, and 2) based on Taylor approximation and using the least error square algorithm, the error due to the frequency difference is calculated and thus the estimated frequency would be updated. One of the main features of the proposed approach is that it can be easily implemented on the available industrial hardware requiring low computational burden. The proposed approach is also robust against noise and harmonics and can track the deviations of the power system frequency as well. The performance of the proposed approach is evaluated through simulation studies and also verified based on implementing it on a prototype synchronizing relay. [ABSTRACT FROM AUTHOR]

Power transformers are of the most critical and expensive equipment in the power system industry. Meanwhile, they are exposed to a variety of faulty and abnormal operating conditions. Therefore, to prevent extension of these events they are protected by different protective schemes. Among the various types of the transformer faults, detecting turn-to-turn faults is the most challenging one for the protection systems. Industrial experiences and standard documents reveal that the existing protection systems include severe shortcomings, and still more efforts are required to offer a reliable method for detecting such faults. To this end, this article puts forward the proposal of a novel turn-to-turn fault detection method to satisfy the basic protection requirements of dependability, security, and speed. This method properly detects the low-level turn-to-turn faults while is stable during system transients and external faults. Performance of the proposed method is evaluated through various experimental and simulation studies. The obtained results verify superior operation of the proposed method under different faults and conditions. [ABSTRACT FROM AUTHOR]