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.

HVDC Circuit Breakers: A Review Identifying Future Research Needs

Energy sustainability and environmental preservation have become worldwide concerns with the many manifestations of climate change and the continually increasing demand for energy. As cities and nations become more technologically advanced, electricity consumption rises to levels that may no longer be manageable if left unattended. The Smart Grid offers an answer to the shift to more sustainable technologies such as distributed generation and microgrids. A general public awareness and adequate attention from potential researchers and policy makers is crucial. This paper presents an overview of the Smart Grid with its general features, functionalities and characteristics. It presents the Smart Grid fundamental and related technologies and have identified the research activities, challenges and issues. It demonstrates how these technologies have shaped the modern electricity grid and continued to evolve and strengthen its role in the better alignment of energy demand and supply. Smart Grid implementation and practices in various locations are also unveiled. Concrete energy policies facilitate Smart Grid initiatives across the nations. Interestingly, Smart Grid practices in different regions barely indicate competition but rather an unbordered community of similar aspirations and shared lessons.

A review of the development of Smart Grid technologies

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.

Microgrid Protection Using Communication-Assisted Digital Relays

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.

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

Feature extraction for fault signals is critical and difficult in all kinds of fault detection schemes. A novel simple and effective method of faulty feeder detection in resonant grounding distribution systems based on the continuous wavelet transform (CWT) and convolutional neural network (CNN) is presented in this paper. The time-frequency gray scale images are acquired by applying the CWT to the collected transient zero-sequence current signals of the faulty feeder and sound feeders. The features of the gray scale image will be extracted adaptively by the CNN, which is trained by a large number of gray scale images under various kinds of fault conditions and factors. The features extraction and the faulty feeder detection can be implemented by the trained CNN simultaneously. As a comparison, two faulty feeder detection methods based on artificial feature extraction and traditional machine learning are introduced. A practical resonant grounding distribution system is simulated in power systems computer aided design/electromagnetic transients including DC, the effectiveness and performance of the proposed faulty feeder detection method is compared and verified under different fault circumstances.

Deep-Learning-Based Earth Fault Detection Using Continuous Wavelet Transform and Convolutional Neural Network in Resonant Grounding Distribution Systems

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

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

This paper focuses on a Smart Fault Diagnostic Approach (SFDA) based on the integration among the output results of recognized dissolved gas analysis (DGA) techniques. These techniques are Dornenburg method, Electro-technical Commission standard (IEC) Code, the Central Electricity Generating Board (CEGB) Code based on Rogers' four ratios, Rogers method given in IEEE-C57 standard, and the Duval triangle. The artificial neural networks (ANN) model is constructed to monitor the transformer fault conditions and trained for each technique individually. The fault decision of each ANN model supplies the proposed integrated SFDA. The integration between these DGA approaches not only improves the fault condition monitoring of the transformers but also overcomes the individual weakness and the differences between the above methods. Toward a better diagnostic scheme, a new SFDA is developed based on the integration of the most three appropriate DGA methods. Further gas concentrations have been considered as raw data (California State University Sacramento (CSUS) as an example) to enhance the proposed SFDA performance. Comparison of each DGA concept with respect to the proposed one is reported, where the results provide evidences of the efficacy of the proposed SFDA.

Integrated ANN-based proactive fault diagnostic scheme for power transformers using dissolved gas analysis

A preliminary description of a new arc representation has been introduced in . In which, the Modified Mayr (P-/spl tau/ model) arc equations are solved in the transient analysis control system (TACS) field of the electromagnetic transient program (EMTP) and represented in the power network by TACS controlled voltage source. In this paper, substantial improvements of this representation are carried out. A performance comparison with the EMTP built-in Avdonin model is incorporated to validate the proposed representation effectiveness. SF6 breakers with experimentally defined arc parameters are used to perform this comparison. The thermal limiting curve is computed by the proposed and the built-in models and compared with the measured characteristic. Also, universality of representation is verified via carrying out different arc model examples of circuit breaker and transmission-line arcing faults. The study results validated the proposed representation regarding accuracy and universality.

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Universal arc representation using EMTP

Electrical faults due to leaning trees are common in Nordic countries. This fault type has been studied in and it was found that the initial transients in the electrical network due to the associated arc reignitions are behavioral traits. In this paper, these features are extracted using the discrete wavelet transform (DWT) to localize this fault event. Wireless sensors are considered for processing the DWTs on a residual voltage of different measuring nodes that are distributed in the network. Therefore, the fault detection is confirmed by numerous DWT processors over a wide area of the network. The detection security is also enhanced because the DWT responded to a periodicity of the initial transients. The term for locating the faulty section is based on the polarity of a specific frequency bandpower computed by multiplying the DWT detail coefficient of the residual current and voltage at each measuring node. The fault due to a leaning tree occurring at different locations in an unearthed 20-kV network is simulated by the alternate transients program/electromagnetic transients program and the arc model is implemented using the universal arc representation. Test cases provide evidence of the efficacy of the proposed technique.

DWT-Based Detection and Transient Power Direction-Based Location of High-Impedance Faults Due to Leaning Trees in Unearthed MV Networks

This paper reviews the major contributions to the high impedance fault (HIF) detection field throughout a 48-year period, from 1960 up to 2008, from classic approaches to heuristic alg ...

Nagy I. Elkalashy

Papers

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

Integrated ANN-based proactive fault diagnostic scheme for power transformers using dissolved gas analysis

Universal arc representation using EMTP

DWT-Based Detection and Transient Power Direction-Based Location of High-Impedance Faults Due to Leaning Trees in Unearthed MV Networks

Approaches in High Impedance Fault Detection - A Chronological Review