The growing environmental challenge of electrical energy systems has prompted a substantial increase in renewable energy generation. Such generation systems allow for significant reduction of CO₂ emissions compared with a traditional fossil fuel plant. Furthermore, several improvements in power systems network configuration and operation combined with new technologies have enabled reduction of losses and energy demand, thus contributing to reduction of CO₂ emissions. Another environmental threat identified in electrical networks is the leaking of insulating sulfur hexafluoride (SF₆) gas used in electrical gas insulated substations (GIS) and equipment. Because of its Global Warming Potential (GWP) of nearly 24,000 and its long life in the atmosphere (over 3000 years), SF₆ gas was recognized as a greenhouse gas at the 1997 COP3; since then its use and emissions in the atmosphere have been regulated by international treaties. It is expected that as soon as an alternative insulating gas is found, SF₆ use in high-voltage (HV) equipment will be banned. This paper presents an overview of the key research advances made in recent years in the quest to find eco-friendly gases to replace SF₆. The review reports the main properties of candidate gases that are being investigated; in particular, natural gases (dry air, N₂ or CO₂) and polyfluorinated gases especially Trifluoroiodomethane (CF₃I), Perfluorinated Ketones, Octafluorotetra-hydrofuran, Hydrofluoroolefin (HFOs), and Fluoronitriles are presented and their strengths and weaknesses are discussed with an emphasis on their dielectric properties (especially their dielectric strength), GWP, and boiling point with respect to the minimum operating temperature for HV power network applications.

This paper examines the data collected from the power industry over the last six years of actual reported emissions of sulphur hexafluoride (SF₆) and the potential impact. The SF₆ emissions have been collated from the 14 different regions in England, Scotland, and Wales (Great Britain) from the six distribution network operators. The emissions of SF₆ due to the transmission network of Great Britain have also been collated from the three different transmission network operators. By collecting this SF₆ emissions data from the power industry, in both the distribution and transmission networks, an overall view of the scale of SF₆ emissions in Great Britain can be evaluated. Data from the power industry also shows the inventory of SF₆ power equipment in use over the last six years in Great Britain and shows the calculated percentage leakage rate of all of this equipment. In this paper, these figures, as reported by the electrical power industry to the UK government, have been used to estimate the likely inventory of SF₆ equipment in England, Scotland, and Wales by 2050 and the future emissions of SF₆ that could be leaked into the atmosphere by this equipment.

This article presents research results on electrical and physic-chemical properties of insulating oil used for high-voltage applications under accelerated artificial thermal aging. Unlike in previously published work, this article gives an extensive set of test data of artificially aged transformer oil under various temperatures. In addition, the aging effect of test temperature on various properties of the oil was quantified. Continuous thermal aging tests were made on transformer oil (Borak 22, Sonelgaz, Nynas, Austria) using a 5000-hr test at four different temperatures of 80, 100, 120, and 140°C. First, the electrical properties of transformer oil, such as the dielectric dissipation factor and the breakdown voltage, are measured after every 500 hr of aging. Next, the physicochemical parameters, including the acidity degree, water content, color factor, kinematic viscosity, density, and flash point, are quantified in order to find the changes in the chemical composition of the insulating oil. The results show that thermal aging significantly affects the properties of transformer oil by the formation of acidic products and the formation of water in oil, which lead to the degradation of the oil's electrical and physicochemical properties.

Dynamic wireless charging (DWC), which enables charging, while electric vehicles (EVs) are in motion, is an attractive charging way. However, additional installed power tracks underneath the lane bring a significant concern to its economic viability. This article proposes a comprehensive framework to evaluate the economic viability of the DWC lane for private EVs. The investment of local power support with renewable energy integration and energy storage is also considered in the DWC system. Charging choices of private EVs among multiple charging providers are modeled to estimate the electricity demand of the DWC system. The grid impact of the DWC system is studied via a multibus ac network. Moreover, an optimization policy is proposed to maximize the DWC provider’s profit and minimize the grid impact by adjusting the charging price and electricity procurement at each horizon. It is found that the payback period of the DWC system with the proposed optimization policy is shortened by 25% compared with the fixed charging price strategy. Even with a tight grid impact limit, the payback period will not be significantly longer under the proposed optimization policy. When the efficiency of the DWC lane increases to 90% and the cost reduces to 50%, the payback period is shortened by 19% and 22%, respectively.

Due to the ever-increasing demand for electricity in the one hand and the environmental constraints to use clean energy on the other hand, the global production of energy from remote renewable sources, particularly from large hydropower plants and offshore wind farms and their connection to the grid are expected to grow significantly in the future. Consequently, the demand to carry this electric power by high voltage direct current (HVDC) technology will increase too. The most suitable HVDC power transmission technology to deliver large amounts of power, exceeding a capacity of 5 GW per bipolar system over long distances with lower losses is by using compact HVDC gas insulated transmission lines (DC GIL) and gas insulated switchgears (DC GIS) with rated voltage (maximum continuous operating voltage) of ±550 kV and 5000 A which are presently under development worldwide. Among the critical challenges for the development of these HVDC gas insulated systems, there are the epoxy cast resin insulators that are used to separate gas compartments also called spacers. Indeed, thorough research studies have been and still being carried out to well understand and clarify the electrical insulation characteristics of HVDC spacers using mainly cylindrical samples and small insulator models, where useful results have been obtained and proposed for implementation in real compact gas insulated systems. However, few practical investigations have been undertaken on real size spacers (product scale) to verify such research outcomes and validate the reliability of the spacers to collect experiences or for commercial use. This paper reviews the current achievements of real size HVDC spacers development. It describes the basic electric field calculation and spacers design, the verification of the insulation performance and validation testing. It gives today’s commercially available compact HVDC GIS/GIL and finally it presents the envisaged future research and development.

An experimental investigation is conducted to measure and correlate the impact of the water content on the electrical characteristics of the mineral oil for transformers, particularly the breakdown voltage, the resistivity, and the dielectric dissipation factor. Regression method is carried out to compare the results obtained through laboratory experiments with those predicted using an analytical model. A treatment to reduce water content in oil involving filtration, degassing and dehydration using a SESCO mobile station was applied to the new, regenerated, and used oil samples in service. The breakdown voltage, the resistivity, and the dielectric dissipation factor of the samples were measured. Regression analysis using an exponential model was applied to examine the samples electrical properties. The results show that, after treatment, the breakdown voltage and resistivity increase as the water content decreases, unlike the dielectric dissipation factor which exhibits a decreasing trend. This trend is found to be similar for the three oil samples: new, regenerated, and used. The results of the regression analysis give close agreement with the experimental results for all the samples and all studied characteristics. The model shows strong correlation with high coefficients (>90%).