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A practical relay algorithm for detecting High Impedance Fault (HIF) is proposed, in which an operational procedure in conjunction with a novel computational algorithm is proposed that has solved the problem of determination of HIF relay's settings, in order that both dependability and security are maintained. In addition, these settings can be tuned according to the changes in the feeder conditions, e.g. topology and load amounts. The discrimination is based on the existence, steadiness and randomness of harmonic energy content of the current waveform. The proposed algorithm is implemented on a DSP. Applying the data for HIF from field tests and for other similar phenomena from simulations has resulted in acceptable security and dependability for the proposed method., (2010 ISA. Published by Elsevier Ltd. All rights reserved.)

This paper presents a novel protection and fault location combined algorithm for mixed overhead transmission lines (OHLs) and underground cables (UGCs). The method is based on applying the Morphological Gradient (MG) to the modal component of synchronized measured currents at both ends of the mixed line to detect the transient components generated by the fault. The proposed method utilizes the sign of superimposed components for discriminating internal and external faults and the difference between the times related to these transient components to detect fault location. The method has been evaluated through various simulations, whereas it has a very low computational burden, it is suitable for online applications. Results have shown high performance of the method against different fault inception angles (FIA), fault resistances, fault types, fault locations, combinations of OHL‐UGC, and even current transformer saturation, noise presence, long cable section, and different sheath‐ground connections. [ABSTRACT FROM AUTHOR]

In this paper, a novel agent based dynamic Volt/Var control approach is introduced, by which the voltage security (i.e., voltage profile and mid- and long-term stability) can be improved and also power loss is reduced under postdisturbance condition and in a wide-area manner. The proposed scheme employs organized multiagent system to preserve voltage magnitude of all busbars within permissible range and reduction of power losses after any disturbance through appropriate coordination of reactive power sources. To accelerate exploitation of on-load tap changers (OLTCs) as well as suppressing the possibility of encountering voltage instability which may be initiated by them, a preventive scheme based on sensitivity analysis is proposed which determines efficient number of multitap changes of OLTCs. To evaluate the effectiveness of the introduced algorithm, different scenarios have been performed in Nordic 32 test system, where the numerical results in all cases demonstrate the effectiveness and reliability of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this paper a predictive scheme for dynamic voltage control is proposed, which maintains voltage security (both voltage stability and voltage profile) of power system, in a wide area manner. The proposed algorithm, upon detecting any voltage violation (both under- and/or over-voltages), employs organized multi-agent system (OMAS) in order to coordinate the employment of reactive power devices in returning voltage magnitudes of all buses to the acceptable range and steady behaviour. In order to achieve high benefits of power system response, each agent takes advantage of a predictive scheme, which is based on the corresponding bus voltage trend. By this predictive characteristic, each agent coordinates its command for remedial action with the prediction of bus voltage destination. Moreover, this predictive characteristic is extended to consider incoming remedial actions (or to compensate the latency in activation of previously decided remedial actions). These predictive characteristics lead to making a smooth waveform and reducing the number of needed remedial actions. The performance of the proposed scheme against different scenarios in Nordic32 test system is presented, where the results illustrate effectiveness and robustness of the proposed scheme. [ABSTRACT FROM AUTHOR]

• Proposing an ultra-fast algorithm for busbar protection. • Responding well to simultaneous faults and internal and external faults with different fault resistances and different FIAs (even 0°). • Applicable to various bus systems including one-and-half bus systems with arbitrary number of bays. • Having immune performance against the presence of noise down to 10 dB. • Having sustained performance as data window moves. This paper presents a new method for fast busbar protection based on S transform of current signals in a substation. In this method high-frequency components of current signals, generated by faults, are extracted by applying fast S transform at the points where current transformers (CTs) of substations are installed. Then, the results are processed and by employing the proposed decision rules, external faults (bay faults and line faults) are discriminated from internal ones. According to the simulation results, the proposed algorithm has high security and dependability and very fast operation and it is immune to fault type, fault inception angle (FIA) and fault resistance. [ABSTRACT FROM AUTHOR]