Hossam E.A. Talaat

An adaptive protection scheme for optimal coordination of overcurrent relays

Abstract 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.

Out-of-step detection based on pattern recognition

Abstract This paper presents a new approach for out-of-step detection of synchronous generators with the ability to initiate early tripping for non-recoverable swings while avoiding tripping on recoverable swings. The approach is based on the K -means clustering pattern recognition technique. The capabilities of the developed algorithm are tested through computer simulation for a typical case study. While being feasible for on-line implementation, the introduced algorithm shows high classification performance.

Predictive out-of-step relaying using fuzzy rule-based classification

This paper presents a new approach of out-of-step relaying based on fuzzy classification. The proposed scheme is equipped with one transducer which is fed by local measurements. The out-of-step relay is designed by selecting the appropriate features, partitioning the pattern space into fuzzy subspaces and inducing a fuzzy if-then rule for each subspace by applying the training set. Then, the designed relay is tested through numerical simulation for a typical study system. Compared to other artificial intelligence (AI)-based schemes, the developed scheme exhibits simpler design, faster on-line operation and better reliability.

Optimal allocation and sizing of Distributed Generation in distribution networks using Genetic Algorithms

This paper addresses the optimization problem of integration of Distributed Generation (DG) in distribution networks. Three Genetic Algorithms (GAs) have been developed to minimize the power losses of the system. The First GA enables the optimal sizing of the DG units given their locations. Alternatively, the second GA determines the optimal locations of the DG units assuming equal sizes of the units. The third GA enables the determination of both optimal sizes, on discrete values, and optimal locations. The results prove the effectiveness of the developed genetic algorithms in finding the optimal penetration level and optimal locations and sizes of the DG units to yield minimum losses of the system.

Distance protection for six-phase transmission lines based on fault induced high frequency transients and wavelets

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, causes some protection problems. This paper introduces a new technique based on wavelet transform for high-speed distance protection of six-phase transmission lines. The technique utilizes a wavelet to capture the fault induced high frequency transient currents superimposed on the power frequency modal currents. The trip decision is based on the relative arrival times of these high frequency signals at the relaying point. The introduced technique is tested and validated through simulation studies. The results show that the technique is accurate and high-speed in fault detection irrespective of the fault type, fault inception angle, and fault resistance. Moreover, it is insensitive to the line terminals and transposition.

Novel alpha-transform distance relaying scheme

This paper presents a simple novel distance relaying scheme based on the 3-D alpha (/spl alpha/)-hyperplane of (V/sub /spl alpha//- I/sub /spl alpha//- P/sub /spl alpha//) representing the relay location measurement at the bus. The nonlinearly transformed voltage, current and apparent power carries information about the fault location and fault condition as bolted or high impedance faults (HIF). The paper describes the tripping mechanism and fault detection conditions in the /spl alpha/-hyperplane for transmission line distance relaying. The scheme is both simple and novel and takes into consideration the quasi dynamic nature of the faults, fault impedance nonlinearity and transmission line capacitance backfeed and resonant oscillations causing amplitude modulation of transmission line segment phase currents. The relay can be easily implemented using analog/digital or hybrid hardware. The relay is based on a transient model and includes all asymmetry and nonlinearity associated with different fault types, fault location, preloading and voltage power angles. The detection is based on transformed /spl alpha/-variables (V, I, P).

A rule-based expert system for distribution system service restoration

This paper presents the application of a rule-based expert system to the service restoration of distribution networks. The principal objective of the developed restoration plan is to minimize the number of switching operations without violating loading constraints in all elements of the network while retaining its open loop structure. The obtained results are encouraging.

Fault detection on radial and meshed transmission systems using fast Hilbert transform

Abstract This paper presents two simple fault detection schemes for radial and meshed transmission systems based on Fast Hilbert transformations of voltage and current signals at the substation terminal. The novel schemes ensure detection accuracy, selectivity and distinction between the two fault types as a bolted/fixed impedance or a high impedance non-linear fault.

Optimal Output Local Control of Multimachine Power Systems

ABSTRACT The local output control of a multimachine power system to improve the dynamic stability studied in this work. A reliable algorithm has been developed to determine the local feedback gains so as to minimize a functional of the error between output vectors of the system separately equipped with optimal controller and the local output controller and also the error between their control efforts. The proposed techniques keeps, on-1ine, a complete autonomy of each interconnected machine by requiring only local variables, which are physically available, to generate the control signal. Eigenvalue analysis and simulation test results for four machine-network are presented to illustrate the efficacy of the method.

Intelligent maximum power tracking and inverter hysteresis current control of grid-connected PV systems

This paper proposes a maximum power point tracking scheme using neural networks for a grid connected photovoltaic system. The system is composed of a photovoltaic array, a boost converter, a three phase inverter and grid. The neural network proposed can predict the required terminal voltage of the array in order to obtain maximum power. The duty cycle is calculated and the boost converter switches are controlled. Hysteresis current technique is applied on the three phase inverter so that the output voltage of the converter remains constant at any required set point. The complete system is simulated using MATLAB/SIMULINK software under sudden weather conditions changes. Results show accurate and fast response of the converter and inverter control and which leads to fast maximum power point tracking.