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Background and aim: Pelvic ring fractures represent a challenge for orthopaedic surgeon. Their management depends on patient’s condition, pattern of fracture and associated injuries. Optimal timing for synthesis is not yet clear. The aim of this study was to define if surgical timing influenced clinic and radiographic outcomes following open reduction and internal fixation for Tile B and C fractures. Materials and methods: 38 patients were included. Patients underwent a clinical examination with the Majeed Score, Iowa Pelvic Score and Orlando Pelvic Score. The radiographic assessment was performed according to Matta Pelvic Score. A statistical analysis of the data compared patients who were operated within 3 weeks (group 1) and those operated later (group 2). Results: Both clinical and radiological outcomes were influenced by timing of surgery. Conclusion: Pelvic ring fractures interest many polytrauma patients and, therefore, their surgical orthopedic approach is frequently delayed as consequence of the severity of the associated clinical conditions. An early surgery of pelvic rong fractures allows a better quality of reduction and osteosynthesis. (www.actabiomedica.it)

This study illustrates how selected instrument voltage transformers (VTs-I) behave in a transitory state. Some laboratory tests are conducted on medium voltage (MV) inductive voltage types to evaluate the voltage transferred from primary to secondary windings when a fast voltage impulse (1.2/50 μs) excites three machines constructively in different ways. Possible effects of metal parts present in the laboratory on the VTs-I behavior are analyzed, and other tests are conducted to determine a suitable shielding for the VTs-I. In order to interpret the experimental results, a theoretical study is performed using a simplified model of the instrument transformer. Finally, characteristic parameters are assigned values that were derived from experimental tests.

International audience; In view of the contemporary scenario and importance of alternative liquid dielectrics, IEEE DEIS Technical Committee on Liquid Dielectrics laid emphasis on pre-breakdown phenomena of ester dielectric fluids. The present article reports the background knowledge on the breakdown theories and behavior of streamers in insulating oils. The major influencing properties of the streamers aroused in liquid insulating systems are discussed keeping in view of the ester based dielectric fluids. Importantly, modelling of streamers, testing approaches, and review of pre-breakdown phenomena in ester dielectric fluids has been presented.

In the last years, the frequency and the intensity of adverse meteorological conditions are on the rise and climate changes have the potential to affect negatively the electrical systems in many different ways. Local or extended electrical outages have been and are caused by extremely severe negative meteorological events of different nature, like strong wind, wet snow, heavy rain and heat waves. Of course, such interruptions of electrical system affect also critical infrastructures with a negative impact on all the human and industrial activities. To face this reality, the Italian Regulatory Authority for Energy, Networks and the Environment (ARERA), established new more stringent rules to maintain high standards of power quality services also through more resilient electrical system. For this reason, there have been established very ambitious benchmark values for the key performance indicators, normally used to evaluate the quality of electric service. With the aim to increase the resilience of the distribution electrical networks, the DSOs are studying and developing new grid operations with improved assets adopting also advanced electrical technologies. For this reason, in the last decades were developed medium voltage cable joints much easier and faster to install. These joints can make the system more vulnerable for possible imperfections introduced during the construction phase for unperfect manpower and for the complexity of the operations.

Natural esters for electrical applications are universally recognized as environmentally friendly and less impact on non-renewable resources consumption. In the framework of an Institutional Group promoted by the University of Roma “La Sapienza”, the National Firefighters Authority, the National Institute for Insurance against Accidents at Work (INAIL) and the Department for Geological Survey of Italy (ISPRA) there were performed several experimental comparative fire/smoke simulations of both mineral and natural ester liquids.

The use of natural ester liquids in power transformers, as an alternative to mineral oils, is increasing in the last decades due to the higher interest in reducing the environmental and fire risks. This is possible thanks to the fact that natural ester liquids present much higher flash & fire points and biodegradability, also satisfying the general principles of a circular economy. Furthermore, their diathermic properties are completely comparable with those of mineral oils and this, if the active part is properly designed, may allow more efficient cooling with a consequent increase in specific power, especially in temporary overload conditions. Also, the electrical properties of mineral oils and natural ester liquids may be considered comparable, especially in terms of AC breakdown voltage and partial discharge behavior when testing these insulating liquids according to standardized methods. The breakdown voltage (IEC 60156) and partial discharges determination (IEC 61294TR) at power frequency are test procedures mainly intended to indicate the presence of contaminants such as water and suspended solid particles. Nowadays, being in progress the preparation of an ASTM Project WK65707 on PD detection in dielectric liquids and being envisaged the revision of the existing Technical Report IEC 61294 TR, in this paper are reported some considerations concerning the influence of different water contents on Partial Discharge Inception Voltage (PDIV) of one commercial natural ester liquid and a traditional mineral oil.

The Partial Discharges Inception Voltage (PDIV) determination is believed to be an important test able to describe the behavior of insulating liquids when subjected to high electrical stress. In IEC standardization body, this test procedure is described by the IEC TR 61294 (Determination of the Partial Discharge Inception Voltage). In particular, according to this standard, the inception voltage is defined as the voltage at which at least one single partial discharge (PD) occurs of apparent charge equal to or greater than 100 pC. On the other hands, partial discharges in insulating liquids are random events which occurs within vapor phase regions located somewhere in the proximity of the cathode. These vapor phase regions may be different in number and in dimension in function of the local field so that partial discharge phenomena appear in terms of PD amplitude distribution in which a single pulse greater than 100 pC cannot be relevant to the overall phenomena. With the aim to establish when a significative PD activity is present in insulating liquids, in this paper different criteria for PDIV determination have been adopted and compared. The results of these tests may be of interest when revising the IEC TR 61294 or considering the actual preparation of an ASTM Standard (Project WK65707 - New Test Method for Partial Discharge Inception Voltage Measurement of Insulating Liquids Using Plane and Needle Electrodes).

The present Special Issue is devoted to papers, which deal with the subjects of liquid dielectrics. Most of the papers included in the present Special Issue are concerned with innovative insulating liquids belonging to the family of natural and synthetic esters. The large interest in ester liquids is due to their positive property to have a much higher flash points and fire points of over 300 °C, almost two times more than traditional mineral oils; in addition, natural esters are readily biodegradable and come from renewable resources, made out of seed crops, such as soybeans. In fact, scientific researches on advances related to these liquids are needed for the development of safer power transformers as essential part of the forthcoming announced green-economy, now no longer postponed for the benefit of our planet. The main validation points for these innovative liquids remain their dielectric behavior and their aging performance and for this reason outstanding researches are still going on. Other papers included in this Special Issue deal with important studies related to breakdown, partial discharge (PD) and the effort made worldwide to improve the liquid insulation properties through the use of innovative nanomaterial additives.

The proposed research work addresses some novelties in the remote control of Low Voltage (LV) distribution networks, namely the development of new technologies and the consequent possible future advances in the sector. More specifically, both capabilities and limitations in current control systems are analyzed, and new processing and remote equipment are proposed for the automated management of distribution networks, with an aim to ensure greater quality and continuity of the electricity service. Moreover, special attention is paid to the remote-controlled equipment from the transformer station to the delivery node, and the main modernization projects proposed by various utilities are compared and commented. The ultimate goals of the different approach here introduced are to obtain a reduction in management costs as well as to guarantee better reliability and safety levels.

Partial Discharges (PD) detection in HV components has shown to be a very powerful diagnostic tool. Anyway, also the acquisition of the same signals in simple insulations, like the dielectric liquids, may give additional information for maintenance of HV components in which they are employed, as in the case of liquid insulated transformers. Among the standardized electrical tests suggested for the insulating liquids, the breakdown voltage (IEC 60156) and partial discharges determination (IEC 61294TR) at power frequency are not basic material properties but test procedures intended to indicate the presence of contaminants such as water and solid suspended matter and the advisability of carrying out drying and filtration treatment. Nevertheless, the PD detection method for insulating liquids actually standardized is based on superseded circuitry and is only addressed to measure the PD Inception Voltages (PDIV). The present paper shows the state of art in PD measurements in dielectric liquids to be taken into account when revising the actual IEC 61294TR or preparing new international Standards (ASTM).

During the summer periods of the last few years there have been unexpected increased numbers of failures of underground cable joints of the medium voltage (MV) network both of e-distribuzione and of other Italian electrical distributors. As a result of this, the University of Roma “La Sapienza” and e-distribuzione started a cooperation with the aim to investigate on causes of such failures and for finding the most appropriate countermeasures in terms of improvement of technologies, operative procedures and operation. This paper reports the main results of a temperature measurement campaign on such MV underground cable joints and an experimental inspection on both failed and not failed cable joints. In this contribution, a discharge mechanism and the ongoing adopted mitigation actions are also presented. The gained information will be useful in re-designing innovative more robust and resilient joints for medium voltage underground cables.

The latest version of the standard IEC 60156 “Insulating liquids - Determination of the breakdown voltage at power frequency - Test method” was published in August 2018 as Edition 3.0. This standard follows the two previously published versions in 1963 and 1995. The test method described in practically all IEC 60156 versions defines a procedure in which the insulating liquid is subjected to an increasing AC electrical field until breakdown occurs and it is used for both acceptance testing on unused liquids at the time of their delivery and for establishing the condition of samples taken in monitoring and maintenance of equipment. In this paper the experimental results of 50 Hz breakdown voltages of both mineral and natural ester liquids performed following the tests methods described in the new edition of IEC 60156 are shown. The tests were performed also with the use of different stirring systems.

The recent evolution in electricity distribution systems has led to the development of new intelligent structures, better known as Smart Grids, Microgrids and Prosumers. The consequent advantages regard mainly both economy aspects and environmental safeguard. In a microgrid, producers and consumers can exchange energy in peer-to-peer way. Normally, the microgrid is connected to a Smart Grid in a single common point. In this case, the microgrid can be easily disconnected from the external grid and continue to work in “island” mode. In this condition, local production must be equal to the energy consumed, unless local storage systems are installed on site. In case of a bidirectional management, the source may change in load and vice versa. In this situation, a traditional transformer may work in an overload condition and the protection system may trip, provoking, in the worst conditions, a blackout. In order to avoid this condition, some solutions are here proposed and commented.

The proposed study concerns the implementation of new strategies aimed at saving energy and reducing the global warming through the reduction of carbon emissions. For this purpose, the implementation of synergic procedures, contemporarily applied to microgrid and prosumers, are proposed and validated in the paper. The main implemented methodologies allow the real time management of different energy flows present inside buildings and, at the same time at higher hierarchic level, enable the supervision and control of the energy managed by the microgrid. The proposed general strategy optimizes contemporarily energy exchanges with the public electricity system, local electrical generation, storage and controllable loads. The developed concepts are valid in general, but also for the port systems where the purpose aims at saving energy and reducing CO2 emissions.

The IEC 61294 Technical Report, published in 1993, describes a simple test procedure to measure the PD Inception Voltage (PDIV) in insulating liquids and doesn’t cover any other items related to the PD patterns and their evolution at higher voltages. This simplified approach should be considered superseded when taking into account the several studies published in the last decades concerning the PD detection in different dielectric liquids using PD patterns and Ultra Wide Band measuring systems with the aim to find a correlation between PD phenomena, breakdown event and liquid characteristics. The use of these advanced PD patterns and Ultra Wide Band detectors may also contribute to discriminate PD in insulating liquids and PD in regular voids in oil-paper insulations.

This paper describes the work carried out by the Italian Institutional Working Group on Natural Esters; this Group has been promoted by the University of Roma ”La Sapienza”, the National Firefighters Authority, the National Institute for Insurance against Accidents at Work (INAIL) and the Department for Geological Survey of Italy (ISPRA) with the objective of further validating the real possibility of risk mitigation for humans and environment through a more widespread use of a new generation of transformers insulated with natural ester liquids. A useful contribution to the activities of the Italian Institutional Group on Natural Esters has been also given by the participation of some of the major players in the electrical sector, such as: Italian TSO, main Distributors, Natural Ester producers and transformer manufacturers. The development of this Italian Group at international level has been the set-up of the CIGRE WG D1.68 “Natural and synthetic esters - Evaluation of the performance under fire and the impact on environment”, which is actually preparing a report on this subject. The present paper reports the main results of experimental comparative fire simulations of both mineral oil and natural esters distribution transformers.

In the framework of the activities of the Italian Institutional Working Group on Natural Esters, smoke production under controlled fire conditions of such innovative insulating liquids has been studied in comparison with that released by traditional mineral oil, normally used in electrical power transformers. This comparison has been made in terms of solid particulates, carbon monoxide (CO), Total Organic Carbon (TOC), Polycyclic Aromatic Hydrocarbons (PAH), Volatile Organic Compounds (VOC) and Aldehydes in different conditions of greater or lower presence of atmospheric oxygen. The main results are reported in this contribution.

Natural esters (triglycerides) possess desirable attributes such as the higher fire points and better environmental compatibility relative to petroleum-derived insulating mineral oil, as a result, the use of such natural esters is on the rise as insulating and heat transfer fluids in electrical devices such as transformers. However, natural esters differ significantly in chemical composition from mineral oils and are more prone to oxidation than mineral oils. High susceptibility of natural esters can be addressed in part through the use of natural esters with higher monounsaturated fatty acid-high oleic natural esters. Recently several high oleic acid soybeans have been introduced commercially. These include Plenish® (Pioneer / Dupont) Vistive Gold® (Monsanto / Bayer) and Soyleic® (Missouri Soybean Association). Both Plenish® and Vistive Gold® are obtained from GMO soybeans, while Soyleic® has been developed through more traditional plant breeding. The oleic acid content of the three natural esters was found to be 79%, 71%, and 81% respectively. While polyunsaturated fatty acid (linoleic and linolenic) contents of the three natural esters were found to be 10.3%, 22.5%, and 7.8% respectively. High oleic soybean oils along with canola oil with oleic content of 75% and polyunsaturated fatty acid content of 17.2% and generic soybean with oleic content of 24.5% and polyunsaturated fatty acid content of 60.0% were subjected to accelerated aging under conditions outlined in IEC 62770 2013. Test results showed that natural esters with higher oleic and lower polyunsaturated acid contents were more stable than the natural esters with lower oleic and higher polyunsaturated content. This stability was reflected in little or no increase in kinematic viscosity and little increase in dissolved acidity. These natural esters are therefore more suitable for dielectric applications where long-term stability is of paramount concern.

High Voltage Direct Current (HVDC) technology will play a more central role in the future grid development than it had in the past due to the technological developments, the increasing use of renewable energy resources and the more ambitious European goals. These evolutions introduce new challenges in power transmission planning and have an impact on the choices of technology and the geographical location of interconnection projects. This paper will give a brief introduction on the benefits that HVDC can provide to the power system, focusing on their penetration in the European system, before dealing with a more detailed description of key HVDC projects in the Italian network.

IEC 60156 and IEC 60897 were standardized with the purpose of evaluating the breakdown voltage of liquid dielectrics both under AC and impulse voltages. AC breakdown voltage determination is a simple method but only able to provide information on the presence of contaminants. The limit of this test is the large scatter in the results and, for this reason, this IEC standard has been recently revised. Impulse breakdown voltage determination allows discrimination of different dielectric liquids, also in terms of their chemical composition. This test has only limited application because of the dimensions of the high voltage generator. The present paper shows a comparison among breakdown voltages of various mineral oils and natural esters under both AC and impulse voltages. The paper presents also an effort to describe how these two tests may reveal the electrical performance of the dielectric liquid under test.

This paper will present natural ester transformer operating data with liquid test results from the units since installation. Various facts and experiences from transformers of two Olympic cities will be shared. The results of physical-chemical and electrical testing including dissolved gas analysis will provide the performance history in the field of a group of power transformers of 138 kV design and of unique designed submersible 10 kV distribution units filled with natural ester fluid, some in service for more than 4 years.

MV underground cable systems are one of the main assets in electrical distribution infrastructures in densely populated urban areas. Experience of several distribution operators (DSOs) has shown an increasing number of failures of MV underground cable joints in the summer period. e-distribuzione, the main Italian DSO, and the University of Roma “La Sapienza” have investigated the causes of these joints failures, ran a temperature measurement campaign on cable joints and performed experimental inspections on both failed and not-failed cable joints. Field observations have been compared with the failure statistics of pre-qualification, type testing and testing after installation of power cables and accessories at KEMA Labs. The relatively high number of failures in testing proves the importance of these tests and awards an insight into failure mode. In this paper are reported the main results of a temperature measurement campaign on such MV underground cable joints and an experimental inspection on both failed and not failed cable joints. In this contribution, a discharge mechanism and the ongoing adopted mitigation actions are also presented. The gained information will be useful in re-designing innovative MV underground cable joints for a more resilient distribution system.

The 2016–2018 ongoing revision of the lEC 60156 “Insulating liquids - Determination of the breakdown voltage at power frequency” was just approved and the revised standard will be published by the end of 2018. This document will include the recommended use of a stirring system with the main purpose to reduce the scatter in the ac breakdown voltage results. The present paper reports a comparison of breakdown voltage mean values and related scatters of two different insulating liquids (traditional mineral oils and natural ester liquids) in accordance with the tests methods of the actual and 2018 upcoming revision of IEC 60156. The results presented here confirm that the modification (stirring system) introduced in the lEC standardized test method, even a simple rearrangement, is able to reduce the scatter of the mean values of the breakdown voltage of the insulating liquids. Some considerations of an alternative test method procedure introduced by the 2018 upcoming revision of lEC 60156 are also reported.

The paper provides, as a first step, a critical, although not-exhaustive, review of the steps required for assessing the resilience of electric distribution systems to natural hazards, and identifies the required metrics and models still to be defined. Aiming to contribute towards that, the paper proposes an empirical-based analytical formula for estimating the expected damage frequencies to underground cable joints, when subjected to overheating. Empirical-based formulas for estimating the damage frequency to underground cables, subjected to earthquakes are also reported in the paper. The implementation of such models within a Decision Support System able to support resilience enhancement decision making processes is briefly illustrated in the paper.

In HVDC submarine cable connections, electrodes design is paramount for technical and economic feasibility. The cathode is designed as simple as possible, if bidirectional operations are not required since reduction reactions does not produce corrosion of the material. The situation is completed reversed for the anodes submersed in seawater: in this case, the corrosion mechanism provokes removal of surface material. For this reason, in order to ensure a sufficiently high lifespan, the anode is usually made of different and more expensive materials, like titanium rods or meshes, coated with layers of a noble metal oxide, such as platinum, or a mixture of several of them. Sometimes the seawater anodes are also immersed in materials based on transition elements such as rare earths. In the present paper, an innovative prototype of seawater anodes, based on steel reinforced concrete, is presented. Moreover, its experimental comparison in seawater at corrosive phenomena is reported, comprising simple steel or titanium bars and titanium meshes protected by special multi metal oxides (MMO). These experiments have shown important reduction of the corrosion phenomena in the case of the prototype of anode made by steel concrete.

This article deals with the implementation of an automated simulator for the optimization of power-flows in blocks of buildings (prosumers) by controlling local generation, storage and consumptions in real-time and simultaneously. Among the advantages of the proposed multi-agent saver, a special emphasis is given to the benefits that may be achieved in carbon reduction and consequent environmental protection. The simulator can be operated in either “Economy” mode to maximize economic profit, or “Energy” mode, for better energy saving. The selection of the ideal strategy depends on a number of factors, among them weather forecasts, kilowatt-hour current rates and the random mechanism of electricity demand associated to the different activities performed within the building.

A prosumer (energy producer-consumer) usually exchanges energy and information with a microgrid, taking into consideration at the same time also such economic aspects as buying or selling energy to the highest bidder based on current rates per kilowatt hour. The proposed study describes the implementation of a new approach that allows to manage in real time the different energy flows inside a building according to a general strategy of simultaneous optimization of electrical generation, storage and controllable loads. On a local level, management may also include more prosumer points, each connected to the microgrid. In this instance, the microgrid supervises and optimizes, at a higher hierarchical level, the various energy flows with consequent synergic, mutual advantages of the different systems, both private and public.

The 20th IEEE International Conference on Dielectric Liquids (ICDL 2019), chaired by Massimo Pompili, was held from June 23 to 27, 2019, hosted by the Faculty of Engineering of University of Roma "La Sapienza". The ICDL 2019 is fully sponsored by the IEEE Dielectrics and Electrical Insulation Society (DEIS), supported by Cargill, Fratelli Parodi, Midel, Baur, Ekofluid, Ergon, Haefely Hipotronics, IET, Nynas, Omicron and Sea Marconi. The conference was chaired by Massimo Pompili in collaboration with Technical Program Chair Luigi Calcara and the Italian CEI (Comitato Elettrotecnico Italiano). IEEE ICDL 2019 is part of a set of conferences addressed, in particular, to physicists, chemists, engineers and, in general, to all those engaged in research and the practical applications of insulating fluids. In addition to traditional topics, this edition of ICDL included special sessions focused on the following items: • synthetic and natural esters in TSO — DSO transformer applications; • alternative gasses on SF6 having much less greenhouse impact; • electrodynamics in emerging applications.

The present paper presents the main results obtained by the Italian Working Group on Natural Esters recently promoted by the University of Rome "La Sapienza", the Firefighters Authority, the Department for Geological Survey of Italy (ISPRA) and the Department of Technological Innovations, Safety of Product, Plants and Anthropic Settlements of the National Institute for Insurance against Accidents at Work (INAIL). This WG on Natural Esters was set up at the beginning of 2016 with the aim of establish the effective possibility of reducing the risks to human health and the environment, through increased spread of innovative transformers insulated with natural esters. In the paper are presented and discussed the following topics: main properties of natural esters and mineral oils; fire risk evaluation of distribution and transmission transformers, including an experimental comparison of fire behavior of natural esters and mineral insulating oils; risk evaluation and different remedial solution for leakage and spill of natural esters and mineral insulating oils.

The 50–60 Hz breakdown voltage of insulating liquids is not an intrinsic property of the dielectric but strongly depends on the presence of contaminants, such as particles and suspended water. Both IEC and ASTM give tests procedures finalized to determine the 50–60 Hz breakdown voltages. This test is adopted as acceptance on new deliveries, testing of treated liquids prior to or during filling into electrical equipment, and monitoring and maintaining oil-filled apparatus in service. Following the IEC Standards, this test has to be performed following the IEC 60156, Ed. 2.0 published in 1995 which is presently under revision. The main reason for revising the standard for the 50–60 Hz breakdown voltage determination of the insulating liquids is the attempt to reduce the scatter in the results, the quantities of the sampling oils and the testing times. The future new edition of IEC 60156 is on the way to reconfirm the present standardized procedure but will recommend the use of a stirring system. Also in an informative annex a new advanced procedure will be included, claiming to be able to reduce the scatter in the determination of the 50–60 Hz breakdown voltages. With the aim to evaluate the mean value and related scatter of power frequency breakdown voltages of insulating liquids, testing time and quantities of samples, this paper presents a comparison of adopted test methods recommended by IEC 60156 and other methods, like the Up-and-Down- and Multiple-Level methods.

One of the parameters that has to be considered in designing underground cables is the thermal resistivity of the soil along their routes. In fact, the ampacity of the MV underground cables having different types of insulation is normally evaluated through the application of the IEC Standard 60287-x “Electric cables — Calculation of the current rating”. This series of IEC Standard is formed of three parts as in the following: part 1: Formulae of ratings and power losses; part 2: Formulae for thermal resistance; part 3: Sections on operating conditions. In Italy, the current capacity of the same MV cables is established by the Italian Standard CEI-UNEL 35027 (2009) “Power cables with rated voltages from 1 kV to 30 kV — Steady state current ratings: cables laid in air and in ground”, which are based on the above mentioned IEC Standard. These thermal ampacities of the underground cables are function of ambient temperature and the thermal resistivity of the soil. The soil thermal resistivity is a parameter not easy to evaluate and for this reason, several times, only typical values are assumed just in function of the kind of the interested terrain (organic, loam, quartz sand, etc.). This assumption ignores the fact that the thermal resistivity varies continuously day by day especially in function of humidity soil content, being strongly dependent from this parameter. This paper describes as important differences of thermal resistivity may be present in consequence of seasonal variation in moisture content of the soil. It is also shown as such variations may cause important anomalous increases of cable maximum working temperature, which may be assumed to be at the origin of unexpected failures especially in correspondence of MV cable joints. In fact, the joints are, still today, the weakest points of the underground cables where the breakdown easily occurs due to poor workmanship, moisture ingress and thermal degradation. This thermal degradation may be also due to circulation of fault current in the metallic sheaths.

Partial discharges in mineral oils take place in the form of pulse bursts within minute microcavities, which are formed at high-electric field charge injection sites. The lifetime of these transient microcavities is determined by the interval between their creation and their ultimate collapse due to dynamic instability. The vapor pressure within these microcavities has been estimated to be as high as 10 MPa and lately there has been considerable speculation as to the nature and type of gases within these microcavities. Currently, carried out experiments indicate that these gases consist principally of hydrogen, ${\rm CH}_{4}$ (methane), and ${\rm C}_{2}{\rm H}_{6}$ (ethane) with smaller traces of other lower molecular weight hydrocarbons.

Aim of the present paper is assessing the technical-economic comparison between three-conductor bundled (3B) and four-conductor bundled (4B) 380 kV overhead transmission lines (OHLs). In both cases, the widely used standard ACSR 31.5 mm is taken as the base conductor. Increasing the number of conductors with respect to the commonly used 3B improves the transport capacity, which can be properly represented in terms of loadability, i.e. the maximum allowable power that can be transmitted for an assigned value of the line length. The consequent higher power limit can be very useful in reducing transmission congestions and, thus, wind-generated energy curtailment that currently is not negligible in Southern Italy, promoting the integration of renewable energy. Moreover, reducing congestions has positive effect in relieving the differences in terms of zonal prices of the electric energy, bringing a further economic benefit for the system. The paper addresses these items performing a technical-economic comparison between a 3B and a 4B 380 kV OHL, assuming basically the same load diagram for both solutions.

Instrument Voltage Transformers (VT) are well known for their critical behavior when subjected to fast impulse voltages. Furthermore, the accuracy of VT is defined by IEC Standards only at power frequency and doesn't consider fast impulse response. Under these conditions the VT may introduce errors in voltage measurements and the transmitted signals may create overvoltages in correspondence of the secondary circuitry and by nominal withstand. The paper reports experimental analysis on Instrument Voltage Transformers response, in time domain, to a fast voltage impulse (1.2/50 µs). The main experimental results on three commercial Instrument Voltage Transformers, having similar features but manufactured by different Producers, are presented and discussed. Also some considerations are reported considering the shielding effects of such components.

The number of HVDC submarine cable connections is increasing around the world. In these applications, electrodes design is paramount for technical and economic feasibility. Cathode's design is kept as simple as possible, if bidirectional operation is not required, since reduction reactions do not produce corrosion of the material. The situation is completey reversed for the anodes submersed in seawater: in this case, the corrosion mechanism could provoke removal of surface material. For this reason, in order to ensure a sufficiently high life span, the anode is usually made of different and more expensive materials, like titanium rods, coated with layers of a noble metal oxide, such as platinum, or a mixture of several of them. Sometimes the seawater anodes are also immersed in materials based on transition elements, such as rare earths. In this paper, an innovative prototype design for seawater anodes, based on steel-reinforced concrete, is presented. An experimental comparison between steel and concrete-steel seawater anodes showing an important reduction of the corrosion phenomena is also presented and discussed in this paper. The basics of the electrodes' electrochemistry is also explained. These basic concepts have shown that the mainly critically of anodes is corrosion by oxidation. Finally, this paper reports some considerations on how to prolong the electrode lifespan of real electrodes as much as possible.

The electrical transformers insulated and cooled with mineral oils remain, still today, the most widespread and effective solution for converting electrical energy. Mineral oils are used for their excellent dielectric and thermal properties, but have a low flash/fire points and biodegradability and these factors may negatively contribute in cases of fire and toxic release with contamination of soil and surface water and groundwater. For these reasons, innovative insulating fluids, such as natural esters (vegetable oils), have been suggested worldwide.

in recent times the new desires for a safer non-flammable, environmental acceptable and less impacting on non-renewable common resources fluid has driven many users in the research and use of alternative fluids to mineral oil.

An innovative tool to prevent the negative consequences of unexpected failure of HV transformers may be based on the risk evaluation. This risk is formed by three partial components, which are: causes of failure, probability that a failure may provoke a damage and type and entity of damages (magnitude). This approach may be very useful for supporting decisions and addressing periodical investments of electrical operators and utilities having in service HV transformers. One of the more important parameter forming the total risk is the Health Index (HI) of the transformers which is normally based on periodical inspection of the units. HI is related with the capability of transformer to withstand to a cause of failure. The present paper described as the application of this practice, able to evaluate the Health Index, has allowed to prevent a possible unexpected failure of a HV transformer, avoiding negative impacts to electric system, environment and operators.

Over the last decade, dibenzyl-disulphide was found to be present in a large number of mineral insulating oils. This sulfur compound tends to react with the copper of the windings, forming harmful byproducts, such as Cu2 S. Different techniques to overcome the problem, including metal deactivation, oil change, and chemical treatment, have been applied. The long-term effectiveness of these techniques is examined and compared.

Recent years have witnessed a relatively large number of power transformer and shunt reactor failures, which were attributed to the presence of corrosive sulfur compounds in the insulating oils and their attending reactions with copper to form electrically conductive copper sulphides. The associated problems appeared to be initially resolved by the addition to the insulating oil small amounts of a metal deactivator (more commonly called passivator), a derivative of 1,2,3 benzotriazole (BTA). However, over the past four years, additional problems arose that were principally associated with the evolution of gases from the electrical insulating oils, containing the metal deactivator. These observations, recorded in the field as well as reproduced in laboratories, are examined in this paper.

The 2019 IEEE International Conference on Dielectric Liquids (ICDL 2019) will be at the University of Roma “La Sapienza” (Italy) on June 23 to 27, 2019. The ICDL 2019 is fully sponsored by the IEEE Dielectrics and Electrical Insulation Society (DEIS).

The relationships between the total copper content, both in dissolved and suspended form, and the dielectric loss characteristics were examined in transformer-type oils. It was established that the dielectric losses in the oils are a function of the total copper content. However, no measurable influence of the sulfur corrosivity of the oils was detected upon the magnitude of the dielectric losses in the oils, notwithstanding that the conductive copper sulfide deposits on the paper tapes impregnated with corrosive sulfur oils resulted in the tapes having highly augmented dielectric losses. It was demonstrated that oil chemical treatment processes that are capable of reducing copper content in the oil, result in a significant improvement of the dielectric losses of the oil.

The behavior of corrosive sulfur in mineral oils is examined in terms of the failures observed in transformers, the surfaces of the copper sulfide covered conductors and degraded paper insulating tapes. The role of dissolved gas analysis (DGA) in the evaluation of the risk of copper sulfide formation is described. The degree of corrosiveness of some sulfur compounds is examined and compared using a Kraft paper wrapped-copper test (standard IEC 62535). The occurrence of DBDS as the most relevant corrosive compound is compared with the presence of other corrosive species in insulating mineral oils. A number of mitigation techniques for corrosive sulfur are described and evaluated.

The partial discharge (PD) pulse burst behavior in natural and synthetic organic ester fluids and mineral oils of the type used in transformers has been examined, using simultaneous wide and narrow band measurement techniques. This permitted the determination and comparison of both the overall charge transfer of the PD pulse as well as that of the discrete PD pulses comprising the PD pulse burst in the evaluated dielectric fluids.