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Distance relay should be blocked during a power swing, but it should operate reliably when any fault occurs even during a power swing. Therefore, this paper introduces a high-speed algorithm based on wavelet transform (WT) to discriminate between a power swing and symmetrical/asymmetrical faults. The algorithm uses a fast mother wavelet, with a 3-coefficient high-pass filter, to decompose the voltage and current signals into their corresponding frequency levels. In this regard, two distinct levels are chosen. The first level of the voltage signal and the eighth level of the current signal are chosen to detect a fault and a power swing, respectively. Depending on the percentage change in the spectral energy of these discriminative signals, the distance relay can discriminate between a power swing and any fault that may occur during a power swing. To evaluate the performance of the introduced algorithm, several faults, including high resistance faults, and power swings cases are simulated on a typical extra high voltage transmission system using MATLAB environment. The simulation results show that the introduced algorithm has a high speed and an efficient performance, even if the signals are noised; where a power swing is detected in a suitable time and faults are detected in a cycle or less.

This paper presents a newly designed scheme based on neural networks to detect loss of excitation (LOE) in synchronous generators. The proposed scheme uses more accurate mechanism and needs fewer parameters in order to achieve fast and reliable detection of LOE. Furthermore, being able to discriminate between LOE and stable power swings is a major concern to enhance the performance of traditional LOE protection. Therefore, the designed network is trained to discriminate between both cases clearly. For training and testing the proposed neural network, MATLAB program has been used for simulation. In addition, by using comparison analysis between the designed network and the previous ones and the traditional MHO relay, the results ensure that the proposed scheme has more secure and fast characters in detecting and discriminating LOE.

Power swing may cause distance relays to operate incorrectly. Hence, this work presents a fast algorithm dependent on wavelet transform to differentiate a power swing from any fault that may occur in series compensated transmission lines. In this algorithm, the Piecewise Linear Spline Wavelet is used to analyze current/voltage waveforms into distinctive levels of frequencies. The eighth level of the single-phase current signal is used to identify power swing and thus to block the operation of the distance relay, whereas the first levels of the three-phase voltage signals are used to identify any fault case even in the presence of power swing, and thus to deblock the distance relay. To assess the efficacy of the presented algorithm, lots events of faults and power swings are examined on a test system modeled in MATLAB/Simulink. The results prove the advantages of the presented algorithm in terms of speed, reliability and efficiency.

This paper presents a high-speed protection scheme for power transmission lines based on wavelet transform (WT). It is a noncommunication protection scheme as it depends completely on locally measured currents. It utilizes WT, which acts as a multi-level bandpass filter, to extract two distinct bands of frequency from the fault induced high frequency (HF) transient currents; the first band is high while the second band is relatively lower. The spectral energies of the extracted signals are then calculated to form two discriminating signals of the relay (operative and restraint). Based on the ratio between these discriminating signals the relay can distinguish whether a fault is internal or external to the protected line. The performance of the introduced protection scheme was evaluated by simulating several faults on 400 kV–50 Hz transmission system using an electro magnetic transient program (EMTDC). The simulation results showed distinct performance of the scheme irrespective of the fault type, fault inception angle, fault position and fault resistance. Moreover, it is not affected by a system configuration and system source parameters.

This paper presents an adaptive protection scheme for optimal coordination of overcurrent relays (OCR) in interconnected power networks with an improved formulation. The scheme adapts to system changes; new relays settings are implemented as load, generation-level or system-topology changes. The software developed for this application is described. The developed scheme is applied to the IEEE 30-bus test system. Results showed the importance and necessity of this scheme in maintaining the optimal performance of the relays under all conditions.

In this paper the problem of directional overcurrent relays coordination in interconnected power networks is presented and solved using the optimization theory. Linear programming with Simplex two-phase method is applied to minimize the operating time of the relays. The insignificance of weighting factors and far-end fault consideration in the problem formulation is proved, through a mathematical example, by simulation, mathematically, graphically and by sensitivity analysis. The current transformer (CT) selection is achieved based on the maximum load and fault currents in order to prevent the miscoordination problem resulting from CT's saturation. A complete algorithm for calculating the optimal operating times is introduced and applied to sample examples.

Six-phase transmission is an optimal solution for increasing the power transmission capability of overhead power transmission lines over existing rights-of-way. This new technology, however, requires a new protection techniques. Therefore, this paper introduces a new technique based on wavelet transform for accurate fault location of six-phase transmission lines. The technique utilizes a wavelet to capture the fault induced high frequency transient currents superimposed on the power frequency currents in a modal domain. The fault location is determined based on the relative arrival times of these high frequency transient signals at the relaying point. The introduced technique is tested and validated through simulation studies. The results show that the technique is accurate in fault location irrespective of the fault type, fault inception angle, and fault resistance. Moreover, it is insensitive to the line terminals and transposition.

This paper introduces a microprocessor and wavelets based non communication relaying approach dedicated for on line six-phase power transmission lines fault detection, classification and faulted phase(s) selection. The approach uses wavelets for capturing the fault induced high frequency signals of currents and/or voltages. The captured high frequency signals are then used in conjunction with their energies to determine the faulted line and consequently for making a trip decision. For this purpose, a suitable wavelet for on line protection is chosen and tuned at a suitable band of frequencies. In order to investigate a real time performance of the introduced approach a microprocessor based laboratory prototype has been implemented and tested. The obtained results show that the approach is high speed in faulted phase(s) detection and insensitive for the fault inception angle, fault resistance, and line terminals.

Six-phase power transmission has many advantages over three-phase transmission but the additional three phases complicate the fault analysis and the required protection. This paper introduces a wavelet-based protection approach for high-speed six-phase power transmission lines relaying. The approach is based on capturing the fault induced high frequency transients, superimposed on the power frequency currents, at a certain band of frequency. The transient energies of the captured signals are then determined and used for fault detection, classification and faulted phase(s) selection. Simulation studies show that the introduced approach is insensitive for the fault inception angle, fault resistance, and system source configuration.