• Energy Research

In low-voltage systems, ground-faults do not necessarily involve the actual earth, but fault currents may return to the source via conductors; such conductors, which provide a clear path toward the source, are defined in applicable codes and technical standards as equipment grounding conductors or protective conductors. The above situation is for example typical of the North American low-voltage multiple grounded distribution systems, also referred to as TN-C-S, in international standards (IEC). In this paper it is substantiated that under ground-fault conditions even healthy equipment, sharing the same protective conductor with faulty equipment, as well as any metalwork in the building, acquire electrical potentials. Such potentials have a decreasing magnitude toward the electrical source and keep the same constant value on equipment located downstream the ground-fault location. The presence of non-zero potential differences between exposed-conductive-parts is a salient trait of TN systems and may constitute a hazard particularly in special locations, such as bathrooms with showers or bathtubs. In such areas, in fact, the resistance-to-ground of persons may be greatly reduced by moisture, water or the absence of clothing. This paper illustrates the advantages of supplementary equipotential bonding connections in such locations as a possible solution in the reduction of latent potential differences.

The application of residual-current principle, as carried out by zero-sequence current protective devices, is one of the most efficient ways to reduce the hazard of electric shock in case of a failure of the equipment's basic insulation to ground. Highly sensitive and regularly tested residual-current-operated circuit breakers without integral overcurrent protection (RCCBs) devices are rightfully recognized worldwide by standards and codes as an effective means to protect persons against direct and indirect contact with energized parts by disconnecting the supply in a timely fashion. These devices are also referred to as ground-fault circuit interrupters. The protective action of the RCCBs, however, can be nullified not only due to internal malfunctions of the device but also due to particular ground-fault conditions. In these dangerous situations for persons, for example, accidental direct contact with two parts at different potentials, the residual current flowing through the RCCB is below its residual operating value, and therefore, it cannot trip. This hazardous circumstance exposes persons to dangerous touch voltages despite the presence of an efficient protective device, which cannot be blamed for not intervening. This paper seeks to clarify these particular fault conditions occurring even in the presence of healthy RCCBs.

The photovoltaic output power varies according to the solar radiation and ambient temperature because the operation of the photovoltaic arrays depends on them. Therefore, achieving the maximum photovoltaic power under different shading patterns is a key factor in the performance improvement of photovoltaic systems. An efficient Maximum Power Point Tracking technique is needed to distinguish the global maximum power point from the local ones, as the traditional techniques are prone to fail. This paper proposes two hybrid meta-heuristic algorithms to improve the maximum power point tracking technique of partially shaded photovoltaic systems. The first proposed maximum power point tracking technique is based on the Whale Optimization Algorithm and Differential Evolution algorithms. The second proposed maximum power point tracking technique is an improved version of the first proposed technique. Both proposed techniques are highly proficient in enhancing the photovoltaic system's efficiency in shaded and unshaded conditions. The maximum power point tracking technique is studied for evaluating the performance based on two traditional algorithms, Whale Optimization Algorithm and Differential Evolution, and two hybrid proposed algorithms. The simulation results show the second proposed maximum power point tracking technique finds the global power points faster and offers better performance than the first proposed technique, which itself outperforms two traditional maximum power point tracking techniques concerning a faster rate of convergence and higher efficiency.

En este artículo, se propone un nuevo restaurador de voltaje dinámico (DVR) alimentado por energía solar fotovoltaica basado en un inversor de fuente Trans-Z (TransZSI) para mejorar la calidad de la energía de los sistemas fotovoltaicos (PV) en la red. El DVR es un compensador electrónico de potencia que se utiliza para inyectar la tensión deseada en el punto de acoplamiento común (PCC) según la perturbación de tensión. En el DVR propuesto, en lugar del VSI tradicional, se presenta TransZSI con méritos sobresalientes de buck/boost, un rango más amplio de ganancia de impulso de voltaje, menos componentes pasivos y menor tensión de voltaje. Para una detección eficiente, una mitigación precisa de las perturbaciones de voltaje y también una disminución de los armónicos de voltaje inyectados, se propone una plantilla de vector de unidad híbrida con un método de control de impulso constante máximo (UVT-MCBC) para TransZSI-DVR. El rendimiento de la TransZSI-DVR propuesta con UVT-MCBC se ha analizado en condiciones de pandeo severo, ligero pandeo con armónicos, hinchamiento e interrupción. Los estudios comparativos y los resultados de la simulación han demostrado la efectividad de la TransZSI-DVR propuesta, a diferencia de la ZSI-DVR y la VSI-DVR tradicionales. El TransZSI-DVR en el sistema fotovoltaico ha mitigado la caída/hinchazón/interrupción del voltaje. También ha mejorado la calidad de la energía tanto de la tensión inyectada al PCC como de la tensión de salida del sistema fotovoltaico. Dans cet article, un nouveau restaurateur de tension dynamique (DVR) alimenté par PV solaire basé sur l'onduleur Trans-Z-source (TransZSI) est proposé pour améliorer la qualité de l'énergie des systèmes photovoltaïques (PV) sur le réseau. DVR est un compensateur électronique de puissance utilisé pour injecter la tension souhaitée au point de couplage commun (PCC) en fonction de la perturbation de tension. Dans le DVR proposé, à la place du VSI traditionnel, TransZSI avec des mérites exceptionnels de buck/boost, une gamme plus large de gain d'amplification de tension, moins de composants passifs et une contrainte de tension plus faible, est mis en avant. Pour une détection efficace, une atténuation précise des perturbations de tension et une diminution des harmoniques de tension injectées, une méthode de modèle de vecteur d'unité hybride avec contrôle d'amplification à constante maximale (UVT-MCBC) est proposée pour TransZSI-DVR. La performance du TransZSI-DVR proposé avec UVT-MCBC a été analysée sous un affaissement sévère, un léger affaissement avec des harmoniques, une houle et une interruption. Les études comparatives et les résultats de simulation ont montré l'efficacité du TransZSI-DVR proposé, par opposition aux ZSI-DVR et VSI-DVR traditionnels. Le TransZSI-DVR dans le système PV a atténué l'affaissement/la houle/l'interruption de tension. Il a également amélioré la qualité de l'alimentation de la tension injectée à la tension de sortie du système PCC et PV. In this article, a new solar PV fed Dynamic Voltage Restorer (DVR) based on Trans-Z-source Inverter (TransZSI) is proposed to improve the power quality of on-grid Photovoltaic (PV) systems. DVR is a power electronic compensator using for injecting the desired voltage to the Point of Common Coupling (PCC) as per the voltage disturbance. In the proposed DVR, in place of traditional VSI, TransZSI with outstanding merits of buck/boost, a broader range of voltage boost gain, fewer passive components, and lower voltage stress, is put forth. For efficient detection, accurate voltage disturbances mitigation, and also lessening the injected voltage harmonics, a hybrid Unit Vector Template with Maximum Constant Boost Control (UVT-MCBC) method is proposed for TransZSI-DVR. The performance of the proposed TransZSI-DVR with UVT-MCBC has been analyzed under severe sag, slight sag with harmonics, swell, and interruption. The comparative studies and simulation results have shown the effectiveness of the proposed TransZSI-DVR, as opposed to traditional ZSI-DVR and VSI-DVR. The TransZSI-DVR in the PV system has mitigated voltage sag/swell/interruption. It has also improved the power quality of both the injected voltage to the PCC and PV system's output voltage. في هذه المقالة، يقترح مرمم جهد ديناميكي جديد يعمل بالطاقة الشمسية الكهروضوئية (DVR) يعتمد على العاكس عبر المصدر Z (TransZSI) لتحسين جودة الطاقة للأنظمة الكهروضوئية (PV) على الشبكة. DVR هو معوض إلكتروني للطاقة يستخدم لحقن الجهد المطلوب إلى نقطة الاقتران المشترك (PCC) وفقًا لاضطراب الجهد. في مسجل الفيديو الرقمي المقترح، بدلاً من VSI التقليدي، يتم طرح TransZSI مع مزايا بارزة من باك/بوست، ومجموعة أوسع من زيادة زيادة الجهد، ومكونات سلبية أقل، وإجهاد جهد أقل. للكشف الفعال، والتخفيف الدقيق من اضطرابات الجهد، وكذلك تقليل توافقيات الجهد المحقون، يتم اقتراح قالب متجه وحدة هجين مع طريقة التحكم في التعزيز الثابت الأقصى (UVT - MCBC) لـ TransZSI - DVR. تم تحليل أداء TransZSI - DVR المقترح مع UVT - MCBC تحت ترهل شديد وترهل طفيف مع توافقيات وتضخم وانقطاع. أظهرت الدراسات المقارنة ونتائج المحاكاة فعالية TransZSI - DVR المقترحة، على عكس ZSI - DVR التقليدي و VSI - DVR. قام TransZSI - DVR في النظام الكهروضوئي بتخفيف ترهل/انتفاخ/انقطاع الجهد. كما أنها حسنت جودة الطاقة لكل من الجهد المحقون لجهد خرج نظام PCC و PV.

In this paper, the implementation of a simulation model for studying the effect of cross-bonding of metallic sheaths and/or non-magnetic armor of single-core medium voltage cables in the same circuit is discussed. With the use of single-core cables, the resistive losses due to the induced circulating currents in cable sheaths or armors causes an increase of cable temperature that reduces its ampacity. In addition, the risk of electric shock due to induced voltages may be present if a person is exposed to the armor/sheath at the unbounded end. For this reason, special bonding techniques are used to significantly reduce these currents. The authors have implemented a model that could be used to help optimize the cross-bonding configuration for single-core cables employed in high-current industrial applications. The model has been experimentally validated thanks to actual data from a medium-voltage underground line.

Forensic engineers have several duties, in some cases to be performed in conflictual situations (e.g. depositions). The competencies of the forensic electrical engineer include the knowledge of engineering standards and best practices, familiarity with applicable laws and regulations, as well as wise decision making. In this paper, functions and duties of the forensic electrical engineer preparing for a trial are discussed and quantitative methods of technical evaluation are proposed.

Microgrids are often considered as the solution for affordable and clean energy in the distribution sector. This article presents the small-signal stability analysis of a distributed generation unit in an autonomous microgrid operation. The purpose of the proposed strategy is to optimally improve the capacity of the power system to restore the reasonable operating condition following a small physical disturbance. The proposed strategy is the joined execution of both the modified antlion optimization algorithm (MALO) and artificial neural network (ANN), and hence it is abbreviated to MALANN. In this article, the proposed controller comprises two control loops, namely the inner current control loop and the outer power control loop. The MALO technique is incorporated to generate the dataset of possible proportional integral (PI) gain parameters. By using the accomplished dataset of MALO, the ANN is trained, and convincing estimate execution is brought out through the entire machine working condition. The proposed strategy is implemented in MATLAB/Simulink, and the results are examined with two test cases and compared with various solution techniques such as base method and ant-lion optimization. The results prove that the stability analysis is reasonably accurate, and the controller offers a reliable system's operation.