Development of a Smart Supercapacitor Energy Storage System for Aircraft Electric Power Systems

This paper presents the development of a supercapacitor energy storage system (ESS) aimed to minimize weight, which is very important for aerospace applications, whilst integrating smart functionalities like voltage monitoring, equalization, and overvoltage protection for the cells. The methodology for selecting the supercapacitor cells type/size is detailed to achieve the safest and most energy-dense ESS. Additionally, the development of the interface electronics for cells’ voltage monitoring and overvoltage protection is presented. The proposed design implements a modular distributed architecture coordinated using communication buses to minimize the wirings and associated complexity and to enable system reconfiguration and expansions, as well as fault diagnoses. Validating the proposed ESS functionalities has been done via experimental testing and the results are presented and discussed.

Silicate conductive composites with graphite-based fillers

Electroconductive composites are modern materials that are commonly used in many industries such as construction industry and machine-building industry. For example, these materials can be useful as sensors for monitoring changes in constructions, shielding stray currents from electrification networks, shielding electromagnetic radiation in operating rooms, cathodic protection against moisture or overvoltage protection of buildings. The topic of this post is the research of electrically conductive silicate composites with graphite-based fillers. In this research will be tested composites with different ratio and types of graphite and monitor their electroconductive properties like impedance, and physical-mechanical properties like compressive and tensile strength. The post describes basic properties and interactions of silicate electrically conductive composites with graphite fillers. It was found that by adding 10 % wt. graphite into silicate composites, impedance is reduced by 50% and compressive strength by 40%. The flexural tensile strength depends mainly on the roughness of the particles, where the coarser flaky particles transfer the load better and increase the strength while very fine graphites reduce the flexural tensile strength. Furthermore, it has been found that very finely ground synthetic graphites are most suitable for achieving low impedance of composites.

Evaluation of the Influence of Lightning Overvoltage Propagation on Wind Turbine and “Mix” Overhead-Cable Lines

Due to the growing demand for new and renewable energies and a favorable geographical position, Vietnam is constructing many wind farms. Besides the advantages of being environmentally friendly and the primary endless source of materials, wind farms have disadvantages, for example, high-structured wind towers are usually built in high, empty places and the resistivity of large soil is vulnerable to lightning damage. In this research, we investigate the effects of overvoltage due to lightning strikes on the wings of wind turbines and propagation causing overvoltage on the insulation of cable in the control cable and mixed-lines. The paper also considers the overvoltage protection measures propagated into the insulation equipment and cable insulation using EMTP-RV simulation software

Study of the Lightning Overvoltage Protection Effectiveness of High Voltage Mixed Overhead Cable Power Lines

In this paper, the effectiveness of lightning overvoltage protection of cables in high voltage overhead cable lines has been analyzed. Because of the high overvoltage level, the cables are protected by surge arresters and by metallic sheath earthing. However, in practice, quite a lot of cases of electricity-evoked damage to the cable outer sheaths are observed, proving that the effectiveness of the protection used is insufficient. As a result, the cables are exposed to environmental factors, especially moisture penetration, which contributes to cable degradation. To explain the causes of this situation, simulation studies were carried out to determine the relevant factors affecting the level of expected overvoltages. The circuit-field model of the overhead cable line in EMTP-ATP, COMSOL and MATLAB software was used for determining overvoltages on the main cable insulation and the outer protective sheath. The studies reveal that the efficiency of the cable insulation overvoltage protection is ensured regardless of the lightning strike location and the crest value of its current. However, the obtained results confirm that no matter the applied protection, the cable outer sheaths may be exposed to overvoltages with higher values than those of the main insulation. Although the analysis was performed for 110 kV lines, the conclusions are general and are also applicable to power lines with higher rated voltages.

Appraisal of electrical wiring and installations status in Isoko area of Delta State, Nigeria

Electricity is the prime mover of every economy; hence there is a need to maintain its generation, distribution and consumption. This study was carried out to appraise the status of electrical wiring in the Isoko area of Delta State, Nigeria. A total of 300 residential buildings, 200 makeshift shops and 100 artisan workshops were sampled and their structures, state of connection, overvoltage protection (cut-out fuse) and earthing were accessed. 100 questionnaires were distributed to electricians involved in electrical wiring and installations in the study area. Results obtained from the questionnaires revealed that only 71% of the residential buildings, 23% of the makeshift shops, and 8% of the artisan workshops made use of electric cables that met the NIS recommendations. For electric cable connections, it was observed that there was a lapse in the connections; mostly in the artisan workshops, as some service cables were not properly tightened to the distribution lines. Only 75% of the residential buildings, 53% of the makeshift shops, and 5% of the artisan workshops had approved rating cut-out fuse. It was observed that in artisan workshops, welding machines were connected directly to the service lines. Furthermore, the results revealed that 42% of the residential buildings, 87% of the makeshift shops and 99% of the artisan’s workshops lacked proper earthing. These results revealed electrical risks in many makeshift shops and artisan workshops and the need for the relevant authorities to act fast to minimize power outrage and prevent electrical tragedies in the study area. Keywords: Artisan, electrical wiring, energy theft, makeshift shops, residential buildings

THE USE OF FERROMAGNETIC AMORPHOUS MATERIALS 5BDSR IN HIGH-FREQUENCY OVERVOLTAGE PROTECTION DEVICES

The paper discusses the prospects of using nanocrystalline amorphous materials in the electric power industry. In particular, in the field of protection of electric power equipment of substations from high-frequency pulses. The effectiveness of using such materials to activate the anomalous skin effect in multilayer conductors is shown. The resulting conductors increase their resistance at lightning frequencies, thereby making it possible to create devices that effectively suppress high-frequency pulses. The authors give an example of a protective frequency-dependent device using nanocrystalline ferromagnetic material and the results of its use in trial operation. The paper shows the results of comparing round and flat frequency-dependent conductors.

Determination of voltage distribution on winding of transformer by state variable method

A transient overvoltage incident at the transformer terminal generates high-frequency voltage fluctuations that have negative impacts on the transformer. These oscillations may cause damage to the insulation of transformers. These problems are heavy, difficult to restore, and repair. Therefore, overvoltage protection for the transformers is essential. This paper pointed out that the interleaved disk winding has a larger capacitance than that of continuous disk windings. Therefore, the use of interleaved disk winding has the effect of making the voltage distribution on the winding wheels more even and increasing the overvoltage resistance of the transformer. In addition, the value of the voltage at each position of the winding when lightning impulses on the transformer terminal and the voltage distribution on the interleaved disk winding at the time when the lightning impulse has maximum value are also presented in the article. On that basis, the effectiveness of using the interleaved disk winding method in the transformer will be analyzed in detail.

Lightning Overvoltage Protection of Step-Up Transformer Inside a Nacelle of Onshore New-Generation Wind Turbines

This paper presents an electromagnetic transient analysis of lightning-initiated overvoltage stresses of the step-up transformers installed inside a nacelle of onshore, multi-megawatt, new-generation wind turbines. The increase in the wind turbine (WT) nominal power output, necessitated introducing the step-up transformer into the nacelle. A transformer installed inside a nacelle is subjected to completely different overvoltage stresses from those present if it were installed at the base of the WT tower. This has serious repercussions on its overvoltage protection (i.e., selection and installation of surge arresters) and insulation coordination. Furthermore, the overvoltage protection of medium-voltage cables (inside the tower) is also problematic when considering their length, proximity to the tower wall, and their screen grounding practices, and needs to be tackled in conjunction with that of the step-up transformer. This paper presents detailed models for the various components of the latest-generation WTs, intended for fast-front transient analysis and assembled within the EMTP software package. We further present the comprehensive results of the lightning-transient numerical simulations, covering both upward and downward (first and subsequent) strikes, their analysis, and recommendations for the optimal selection of medium-voltage surge arresters for the step-up transformers installed inside a nacelle.