H.A. Darwish

Bio: H.A. Darwish is an academic researcher from Menoufia University. The author has contributed to research in topics: Emtp & Circuit breaker. The author has an hindex of 4, co-authored 7 publications receiving 153 citations.

Modeling and experimental verification of high impedance arcing fault in medium voltage networks

Abstract: A high impedance arcing fault due to a leaning tree in medium voltage (MV) networks is modeled and experimentally verified. The fault is represented in two parts; an arc model and a high resistance. The arc is generated by a leaning tree towards the network conductor and the tree resistance limits the fault current. The arcing element is dynamically simulated using thermal equations. The arc model parameters and resistance values are determined using the experimental results. The fault behavior is simulated by the ATP/EMTP program, in which the arc model is realized using the universal arc representation. The experimental results have validated the system transient model. Discrete wavelet transform is used to extract the fault features and therefore localize the fault events. It is found that arc reignitions enhance fault detection when discrete wavelet transform is utilized

Enhanced Commutation Circuit Design of hvdc Circuit Breaker Using EMTP

Abstract: In this paper, electromagnetic transient program (EMTP) aided design tool for active commutation circuit of an HVDC circuit breaker is presented. The breaker arc is modeled using the modified Mayr equations, and its interaction with the active commutation circuit is considered in a novel manner. Based on this simulation, an iterative methodology is developed to determine the most suitable elements of the commutation circuit. The performance of the designed breaker is tested using an equivalent test circuit. Then, the breaker interruption capability is examined for different current levels to validate its effectiveness. The test results have shown that the proposed design procedure is competitive to the experimental one

Real-time testing of hvdc circuit breakers Part 1: bench test development

Abstract: In this paper, a new real-time testing technique for hvdc circuit breakers using the Electromagnetic Transient Program (EMTP) is presented. Full-size controlled converters are accurately modeled and different system topologies with hvdc circuit breakers are considered. Breaker miscellaneous switching duties are examined. The test results show that most of the system transients produced by the dc link and converter controls influencing breaker interruption are considered. Nearly exact realtime tester for hvdc breakers is developed for the first time.

Operation evaluation of DWT-based earth fault detection in unearthed MV networks

Abstract: A novel selectivity technique to estimate the faulty feeder in MV networks was introduced in [1]. This technique depended on the directionality of discrete wavelet transform (DWT) detail coefficient of a residual current of each feeder with respect to the DWT detail coefficient of the residual voltage. The algorithm efficacy has been examined with high impedance arcing fault due to leaning trees. In this paper, the algorithm performance is tested with resistance earth faults over a wide range of the fault resistance values (1 mOmega to 100 kOmega) as well as concerning practical fault cases such as arcing faults. The fault cases occurring at different locations in an unearthed 20 kV network are simulated by ATP/EMTP. Test cases confirm the efficacy of the proposed technique.

Real-time testing of hvdc circuit breakers part II: real-time cases

Abstract: A new real-time testing technique for hvdc breakers using the Electromagnetic Transient Program (EMTP) has been proposed. In this paper, different topologies of hvdc systems with full-size controlled converters are accurately modeled and the hvdc circuit breakers are appropriately located. Then, miscellaneous switching duties are examined. Metallic Return Protecting Breaker (MRPB) and fault clearing processes are fully analyzed for the first time. The test results validate the efficacy of the proposed real-time testing procedure.

HVDC Circuit Breakers: A Review Identifying Future Research Needs

Abstract: The continuously increasing demand for electric power and the economic access to remote renewable energy sources such as off-shore wind power or solar thermal generation in deserts have revived the interest in high-voltage direct current (HVDC) multiterminal systems (networks). A lot of work was done in this area, especially in the 1980s, but only two three-terminal systems were realized. Since then, HVDC technology has advanced considerably and, despite numerous technical challenges, the realization of large-scale HVDC networks is now seriously discussed and considered. For the acceptance and reliability of these networks, the availability of HVDC circuit breakers (CBs) will be critical, making them one of the key enabling technologies. Numerous ideas for HVDC breaker schemes have been published and patented, but no acceptable solution has been found to interrupt HVDC short-circuit currents. This paper aims to summarize the literature, especially that of the last two decades, on technology areas that are relevant to HVDC breakers. By comparing the mainly 20+ years old, state-of-the art HVDC CBs to the new HVDC technology, existing discrepancies become evident. Areas where additional research and development are needed are identified and proposed.

Microgrid Protection Using Communication-Assisted Digital Relays

Abstract: Microgrids have been proposed as a way of integrating large numbers of distributed renewable energy sources with distribution systems. One problem with microgrid implementation is designing a proper protection scheme. It has been shown that traditional protection schemes will not work successfully. In this paper a protection scheme using digital relays with a communication network is proposed for the protection of the microgrid system. The increased reliability of adding an additional line to form a loop structure is explored. Also a novel method for modeling high impedance faults is demonstrated to show how the protection scheme can protect against them. This protection scheme is simulated on a realistic distribution system containing a high penetration of inverter connected Distributed Generation (DG) sources operating as a microgrid. In all possible cases of operation the primary and secondary relays performed their intended functions including the detection of high impedance faults. This system is simulated using Matlab Simulink's SimPowerSystems toolbox to establish the claims made in this paper.

Detection of High Impedance Fault in Power Distribution Systems Using Mathematical Morphology

Abstract: A high impedance fault (HIF) is characterized by a small, nonlinear, random, unstable, and widely varying fault current in a power distribution system. HIFs draw very low fault currents, and hence are not always effectively cleared by conventional overcurrent relays. Various schemes are proposed to detect such faults. This paper presents a method to detect HIFs using a tool based on mathematical morphology (MM). The method is implemented alongside the conventional overcurrent relay at the substation to improve the performance of this relay in detecting HIFs. It is rigorously tested on standard test systems using PSCAD/EMTDC® to generate test waveforms, and Matlab® to implement the method. Simulation results show that the proposed method is fast, secure, and dependable.

Arc Fault and Flash Signal Analysis in DC Distribution Systems Using Wavelet Transformation

Abstract: Arc faults have always been a concern for electrical systems, as they can cause fires, personnel shock hazard, and system failure. Existing commercialized techniques that rely on pattern recognition in the time domain or frequency domain analysis using a Fourier transform do not work well, because the signal-to-noise ratio is low and the arc signal is not periodic. Instead, wavelet transform (WT) provides a time and frequency approach to analyze target signals with multiple resolutions. In this paper, a new approach using WT for arc fault analysis in dc systems is proposed. The process of detecting an arc fault involves signal analysis and then feature identification. The focus of this paper is on the former. Simulation models are synthesized to study the theoretical results of the proposed methodology and traditional fast Fourier transform analysis on arcing faults. Experimental data from the dc system of a photovoltaic array is also shown to validate the approach.