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La2Ti2O7 ceramic has a perovskite-like structure with super-high Cuire temperature (Tc ~ 1460 ℃), which is an excellent candidate for the application as a high-temperature accelerator sensor used at beyond 1000 ℃. The high temperature electrical conductivity resulting from charge carrier transport has a major influence on the sensitivity of sensors. Here, Zn was introduced as an acceptor into La2Ti2O7 ceramics for high-temperature electrical properties. All the samples show pure perovskite-like structure with P21 space group and compact microstructure. With the introduction of Zn up to x = 0.08, the insulation resistance of the ceramics was enhanced more than 1000 times. Impedance spectroscopy and modulus spectroscopy were used to investigate the high-temperature transport of charged carrier. Interestingly, the acceptor doping resulted in an increasing concentration of oxygen vacancies, but a significant increase in both electrical insulation and activation energy of the ceramics was observed. The thermal activation mechanism is responsible for the high-temperature charge carrier transport. It is suggested that although the concentration of oxygen vacancies increase, Zn doping depresses the motion of oxygen vacancies in perovskite-like structure. The results provide a method to improve the insultation of high-temperature piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

BaTiO 3 -based ceramic is considered to be a fascinating dielectric material with high reliability for ultra-thin multilayer ceramic capacitors (MLCC). Here, we fabricated a series of acceptor-doped BaTiO 3 (Mg: 0.2, 0.5, 1.0, 1.5, 2.0, and 5.0 mol%) ceramics with Al 2 O 3 and SiO 2 as sintering additives. With an increase in Mg concentration, the insulation resistance of the BaTi 1- x Mg x O 3 ceramics initially increases and then decreases, in which the 0.5 mol% Mg-doped ceramic achieves superior degradation behavior. The reason is that with the incorporation of the acceptor ion Mg2+, the charge compensation mechanism in the system changes. Initially, barium vacancy is generated, which is gradually dominated by oxygen vacancy. Analysis indicates that the segregation of the acceptor state barium vacancy to the grain boundary increases the schottky barrier of the grain boundary, while the gradual increase of the donor state oxygen vacancy reduces the reliability of the ceramic. This study provides a comprehensive overview illustrating the significant role of point defects in the potential barrier of the grain boundary in acceptor-doped BaTiO 3 ceramics. It identifies a pathway to achieve high reliability in BaTiO 3 -based MLCC. [ABSTRACT FROM AUTHOR]

It is known that cable channels, often consisting of multilayer polymer pipes, are used to protect cable lines. Taking into account the fact that cables are heated during operation, important criteria for the reliability of the cable channel are increased heat resistance and flame resistance - for the inner layer of the pipe. Even the most reliable system cannot completely eliminate the possibility of cable damage up to a short circuit in the line. In case of cable breakage, bare wires will be located on the wall of the polymer pipe. In this case, finding the place of cable breakage through the wall of a pipe traditionally made of HDPE dielectric is extremely difficult. When choosing a cable channel of a special design made of special electrically conductive PCM, even in case of damage to the conductive line, it will be possible not only to avoid further destruction, but also to determine the breakdown location. In the assortment of POLYPLASTIC Group there are fundamentally new technical, technological and constructive solutions of current-seeking pipes for cable channels produced under the trademark ELECTROPIPE OS RS OMP, which allows you to determine the place of cable breakdown with an accuracy of up to 12 m. The paper presents a comparative study of multilayer polymer pipes of the ELECTROPIPE RS series, ELECTROPIPE OS RS with an internal refractory layer and ELECTROPIPE OS RS OMP with an internal electrically conductive layer based on a special refractory composition and carbon nanotube concentrate (CNTC). The content of CNTC is 5–10 wt %. All tests were carried out on real pipe samples. The physicomechanical (tensile strength, modulus of elasticity and elongation) and electrophysical characteristics (insulation resistance), as well as resistance to flame (exposure to hot wire, a test for flammability according to the ROSSETI method) were investigated. [ABSTRACT FROM AUTHOR]

The medium-voltage components in the ignition installations for gasoline engines contain electroinsulating materials that lose their properties over time. The purpose of this paper is to measure and analyze the insulation resistance, dielectric absorption ratio and polarization index of the insulation of materials (three types of materials) used for medium-voltage distributors, for several operating periods, in automotive ignition installations. Experiments were conducted with old (operation tens of thousands of km, some with surfaces that have been cleaned) and new medium-voltage distributors, and a megohmmeter was used to measure, over time, the insulation resistance between the central terminal and the output terminals at different test voltages. The insulation resistance of the distributors depends on the use: in the old ones, they have values of tens of GΩ (e.g., up to 100 GΩ) and, in the new ones, of the order of TΩ (e.g., 4–7 TΩ). The more distributors are used, for the same distributor, there are greater differences between the measurements made between terminals and the average values (87% for used distributors, respectively, 2% for new ones). For new or less used distributors, higher values were obtained for the dielectric absorption ratio (1.26–1.27; for used ones, 0.91–0.95) and polarization index (1.15–1.25; for used ones, 0.96–1.15). The results show the importance of the volume insulation resistance of the electroinsulating material compared to the surface resistance and the insignificant improvement when cleaning the internal and external surfaces of the medium-voltage distributors. [ABSTRACT FROM AUTHOR]

The monitoring of electrical insulation resistance is one of the most important parameters characterizing the reliability of the on-board electric-power system and the safety of its operation. A significant part of the faults and failures inherent in elements of the shipboard power system is associated with reducing insulation electric resistance with respect to the ship hull caused by exposure to high humidity and temperature, as well as mechanical damage to the insulating layer, electrical cables, wires, and electrical devices. The rules of technical operation establish the lowest values of insulation resistance of the elements of the onboard electric-power system with respect to the ship hull. At the same time, the presence of highly branched electrical networks on the ship complicates the problem of centralized and localized insulation resistance monitoring. In addition, the increase in the number of power plants and possible changes in the number of concurrent consumers within the power system, as well as an increase in the contribution of high-voltage electrical onboard equipment, requires a more reliable control system for electrical insulation resistance. The author concludes that, to provide more reliable insulation resistance monitoring of the elements of an onboard power system, it seems relevant to additionally use novel principles and methods for controlling the measurement information in the monitoring system and processing this information, which differ from those traditionally used in the construction of such systems. For this purpose, as well as to improve the characteristics of the insulation resistance monitoring of the electric-power system, it has been proposed to apply the queuing theory with the assessment of its parameters. The onboard presence of a system for the continuous automatic monitoring of insulation resistance is an important component that provides the reliability and safety of ship operation by its crew. [ABSTRACT FROM AUTHOR]

Insulation resistance is a vital factor in dry DC link capacitors (DCLCs), and crucially influences their voltage equalization and energy storage performance. However, at present, there is a lack of experimental observation on the insulation resistance characteristics of DCLCs in the presence of high temperatures and operating voltages. In the present study, the insulation resistance and conductivity of DCLCs are methodically analyzed. For this purpose, the corresponding test platform is appropriately fabricated, the insulation resistance measurement experiments are performed at various temperatures and operating voltages, and the factors affecting the insulation resistance and conductivity of the DCLC are carefully examined. The results reveal that the insulation resistance of the DCLC reduces exponentially with the growth in voltage and operating temperature. When the operating voltage becomes greater than 4480 V or the operating temperature reaches higher than 70 °C, the decline in insulation resistance slows down. The conductivity of metalized polypropylene film in the DCLC increases exponentially with increasing voltage and temperature. By increasing the operating voltage from 1960 V to 5600 V and the temperature from 20 °C to 90 °C, the DCLC's insulation resistance exhibits a descending trend from 891.30 MΩ to 2.14 MΩ, while its conductivity grows from 3.49 × 10−16 S/m to 1.47 × 10−13 S/m. The results reveal that the key factors affecting the insulation resistance of the DCLC are the polypropylene film and the metal evaporated from the metal layer. This research is anticipated to provide a valuable reference for the further development of science and technology pertinent to the insulation resistance of DCLCs. [ABSTRACT FROM AUTHOR]

Insulation resistance (IR) is an essential metric indicating insulation conditions of extruded power cables. To deliver reliable IR simulation as a reference for practical cable inspection, in this paper, four IR degradation models for cross-linked polyethylene-insulated cables under thermal ageing are presented. In addition, the influences of methodologies and temperature profiles on IR simulation are evaluated. Cable cylindrical insulation is first divided into sufficiently small segments whose temperatures are simulated by jointly using a finite volume method and an artificial neural network to model the thermal ageing experiment conditions. The thermal degradation of IR is then simulated by dichotomy models that randomly sample fully degraded segments based on an overall insulation (layer) ageing condition estimation and discretization models that estimate the gradual degradation of individual segments, respectively. Furthermore, uniform and non-uniform temperature profiles are incorporated into dichotomy and discretization models, respectively, for a comparison. The IR simulation results are not only compared between different models, but also discussed around the sensitivity of IR simulation to segment sizes and degradation rates. This provides cable assessment engineers with insights into model behaviour as a reference for their selection of appropriate IR degradation models. [ABSTRACT FROM AUTHOR]

Isolators are one of the assets at PT PLN, which serve as separators between the energized and non-energized parts. Maintenance is performed by replacing damaged isolators when there are indications of reduced insulation resistance. In this journal, the insulation resistance values were measured using a Kyoritsu Insulation Tester and six porcelain isolator samples in various conditions were used. The aim was to determine the extent of the decrease in insulation resistance values, as well as the leakage current and touch voltage values based on Ohm's law formula. Based on the measurement results, the sixth isolator in partially damaged condition is the worst, supported by an insulation resistance value of 800 MΩ for a test voltage of 10kV and 400 MΩ for a test voltage of 5kV. In good condition, the measured insulation resistance value of the isolator is 1 TΩ. Based on the calculation results, in the sixth condition, the leakage current values were 6.25 mA and 25 mA, and the touch voltage values, assuming an average human insulation resistance value of 1000 Ω, were 6.25 Volts and 25 Volts. According to 0520-2.K.DIR.2014 standards, the insulation resistance values meet the requirement that 1kV insulation resistance can be sustained by 1MΩ and are still below the maximum touch voltage limit, which is < 50V effective. [ABSTRACT FROM AUTHOR]

The medium-voltage components in the ignition installations for gasoline engines contain electroinsulating materials that lose their properties over time. The purpose of this paper is to measure and analyze the insulation resistance, dielectric absorption ratio and polarization index of the insulation of materials (three types of materials) used for medium-voltage distributors, for several operating periods, in automotive ignition installations. Experiments were conducted with old (operation tens of thousands of km, some with surfaces that have been cleaned) and new medium-voltage distributors, and a megohmmeter was used to measure, over time, the insulation resistance between the central terminal and the output terminals at different test voltages. The insulation resistance of the distributors depends on the use: in the old ones, they have values of tens of GΩ (e.g., up to 100 GΩ) and, in the new ones, of the order of TΩ (e.g., 4–7 TΩ). The more distributors are used, for the same distributor, there are greater differences between the measurements made between terminals and the average values (87% for used distributors, respectively, 2% for new ones). For new or less used distributors, higher values were obtained for the dielectric absorption ratio (1.26–1.27; for used ones, 0.91–0.95) and polarization index (1.15–1.25; for used ones, 0.96–1.15). The results show the importance of the volume insulation resistance of the electroinsulating material compared to the surface resistance and the insignificant improvement when cleaning the internal and external surfaces of the medium-voltage distributors.

In the mass production of multi-element silicon p-i-n photodiodes, the problem of systematic rejection of products due to a decrease in the insulation resistance between the active elements of photodetectors has been revealed. The purpose of this work is to study the causes of insulation resistance degradation and to establish optimal methods for avoiding this phenomenon. A comparative analysis of three insulation methods was carried out: classical insulation by the surface of a non-conductive substrate and a dielectric layer; insulation by means of mesaprofile grooves with a dielectric film; insulation by means of areas of limitation of surface leakage channels isotypic with the substrate material (in this case, p+-type) formed in the gaps between active elements. The study found that the reason for the deterioration of the insulation resistance between the active elements of photodiodes is the presence of conductive inversion channels at the Si-SiO2 interface due to the use of silicon with high resistivity. One mechanism for the formation of inversion channels is the redistribution of impurities in the masking oxide (in particular, phosphorus) and their diffusion to the interface during thermal operations. Another mechanism for the formation of inversion layers is the diffusion of boron from silicon into SiO2 during heat treatment due to the fact that the boron segregation coefficient is less than one. In the manufacture of samples with insulation using non-conductive areas of the substrate, a decrease in insulation resistance was observed as the technological route was performed (after each subsequent operation, the resistance degraded). The degree of degradation can be reduced by reducing the duration of thermal operations. It has been shown that reducing the thickness of the masking oxide causes a decrease in insulation resistance. When using mesa-technology, it is possible to increase the insulation resistance by eliminating the high-temperature oxidation operation and, in fact, due to the absence of a masking coating during phosphorus deposition. Insulation by means of p+-type areas in the gaps between the active elements allows to obtain the highest insulation resistance values. The formation of these regions with a width of 100 μm in the gaps with a width of 200 μm allowed us to obtain an insulation resistance of 25-30 MΩ. To ensure the insulation of the active elements of photodiodes by this method, two thermal operations are added to the technological route. The number of thermal operations can be reduced by doping the entire silicon surface with a low boron concentration before forming a masking coating.

Herein, we present results that emphasize the importance of retaining high insulation resistance in polymer backsheets for the reliable operation of photovoltaic installations. By correlating inverter monitoring data, meteorological data, and spectroscopic information from backsheet materials of photovoltaic modules, we derive performance and degradation rates for inverters connected to photovoltaic modules with several backsheet types. The feasibility of evaluating the degradation status of photovoltaic modules in the field through spectroscopic analysis of the water content in backsheet and encapsulant is demonstrated. We show that an increase in water content is a sign for reduced leakage resistance. Ground impedance was measured alongside relative humidity and temperature for three specific backsheet types. Inverters with polyamide and fluorinated coating/polyethylene terephthalate backsheets showed a significant drop in ground impedance at high humidity, RH > 70%. A loss rate of −2 kΩ/day in ground impedance was found for inverters connected to modules with certain fluorinated backsheets. This value is twice as high as for inverters connected to modules with polyamide backsheets. Time series show that the sensitivity to moisture and water ingress increases with time, especially for modules with polyamide and certain fluorinated backsheets. The worst degradation scenario observed had an annual yield loss of 27% due to inverter outages on humid days. About 25% of inverter trip alerts after 8 years of operation included modules with the specific fluorinated backsheet. In general, the study revealed a distinct backsheet impact on ground impedance and operation of inverters and the resulting yield showing an important role of the choice of polymers for reliable and long‐lasting photovoltaic systems. [ABSTRACT FROM AUTHOR]

The results of studying the effect of thermal-treatment modes and finishing conditions on the rupture strength of woven-glass tapes and fiberglass fabrics and electrical insulation manufactured from them are reported. It is shown that the complete removal of the oiling agent "wax emulsion" from the surface of glass tapes is attained after stepwise thermal treatment at 250–400°C, but the rupture strength decreases by 80% in this case. The finishing of glass tapes with 3-glycidoxypropyltrimethoxysilane after the technical oiling agent is completely removed restores their rupture strength to the level of 35–40% of the initial value (before removing the wax-emulsion oiling agent) and makes it possible to create electrical insulation with water resistance to 1100 h at 23°C and to 7 h at 80°C. [ABSTRACT FROM AUTHOR]

This article presents the results of the development of silicon coordinate p-i-n photodiodes (PD) with improved parameters. The technological possibilities of reducing the gaps between the responsive areas of multi-element PDs were studied. PDs with reduced gaps were modeled, samples were made according to the models, the parameters of the obtained PDs and the influence of various technological factors on their values were investigated. During research, it was established that the factor that limits the possibility of reducing the gaps is the insulation resistance between the responsive elements. The decrease in the insulation resistance between the PD elements was a consequence of the formation of inversion leakage channels at the Si-SiO2 interface, which is characteristic of high-resistance p-type silicon, the conductivity of which increased with a decrease in the width of the gaps. To increase the resistance of the gaps between the platforms and reduce the influence of inversion layers, it was decided to form regions of the restriction of the leakage channels between the REs – highly doped regions isotypic with the substrate material (p+-type). They will prevent the movement of current carriers that are generated in the inversion layers on the surface of the substrate. Four-element p-i-n photodiodes with 31 μm gaps between the sites were made. The proposed PD is not significantly inferior in parameters to analogues, but it is the sample with the smallest gaps between RE among photodiodes of the same type and size in the world market. The improvement of the insulation resistance between the REs made it possible to reduce the level of dark current of the PD by twice compared to serial products, with a slight decrease in responsivity due to the introduction of additional thermal operations into the technological route. In particular, the dark current density of the RE of experimental PDs was 40-80 nA/cm2, compared to 80-250 nA/cm2 for commercial samples. Impulse current monochromatic sensitivity at a wavelength of 1064 nm for experimental samples was 0.41-0.44 A/W, and for commercial ones - 0.45-0.48 A/W.

Durability of photovoltaic (PV) modules is of great concern not only from the point of view of cost‐effectiveness but also from the point of view of safety and sustainability. The backsheet of a PV module is one of the most critical parts of the PV module from the point of view of protection and also one of the most important sources of PV modules' failure; hence, it is of great importance to understand its different forms of failure. In this paper we analyze the case of an 8‐MW PV plant, which had suffered a rapid degradation of their PV modules' backsheets. The case is especially relevant as all the PV modules are from the same model and manufacturer but with different backsheet materials (polyamide and fluoropolymer) and different times of exposure: on one hand, all PV modules originally installed in the plant (i.e., 6 years under operation when tested), and also, extra modules that had been stored indoors for replacement and had been mounted in the plant for less than 1 year when tested, serving as reference modules. In this paper we present the signs of degradation of these PV modules after different times of exposure under real operation using different on‐field and laboratory tests. We propose different techniques for rapid diagnosis of backsheet degradation so that the problem can be detected at a very early stage, before it results in major energy losses or in safety issues. [ABSTRACT FROM AUTHOR]

Insulation resistance (IR) is an essential metric indicating insulation conditions of extruded power cables. To deliver reliable IR simulation as a reference for practical cable inspection, in this paper, four IR degradation models for cross-linked polyethylene-insulated cables under thermal ageing are presented. In addition, the influences of methodologies and temperature profiles on IR simulation are evaluated. Cable cylindrical insulation is first divided into sufficiently small segments whose temperatures are simulated by jointly using a finite volume method and an artificial neural network to model the thermal ageing experiment conditions. The thermal degradation of IR is then simulated by dichotomy models that randomly sample fully degraded segments based on an overall insulation (layer) ageing condition estimation and discretization models that estimate the gradual degradation of individual segments, respectively. Furthermore, uniform and non-uniform temperature profiles are incorporated into dichotomy and discretization models, respectively, for a comparison. The IR simulation results are not only compared between different models, but also discussed around the sensitivity of IR simulation to segment sizes and degradation rates. This provides cable assessment engineers with insights into model behaviour as a reference for their selection of appropriate IR degradation models.

Insulation resistance is a vital factor in dry DC link capacitors (DCLCs), and crucially influences their voltage equalization and energy storage performance. However, at present, there is a lack of experimental observation on the insulation resistance characteristics of DCLCs in the presence of high temperatures and operating voltages. In the present study, the insulation resistance and conductivity of DCLCs are methodically analyzed. For this purpose, the corresponding test platform is appropriately fabricated, the insulation resistance measurement experiments are performed at various temperatures and operating voltages, and the factors affecting the insulation resistance and conductivity of the DCLC are carefully examined. The results reveal that the insulation resistance of the DCLC reduces exponentially with the growth in voltage and operating temperature. When the operating voltage becomes greater than 4480 V or the operating temperature reaches higher than 70 °C, the decline in insulation resistance slows down. The conductivity of metalized polypropylene film in the DCLC increases exponentially with increasing voltage and temperature. By increasing the operating voltage from 1960 V to 5600 V and the temperature from 20 °C to 90 °C, the DCLC’s insulation resistance exhibits a descending trend from 891.30 MΩ to 2.14 MΩ, while its conductivity grows from 3.49 × 10−16 S/m to 1.47 × 10−13 S/m. The results reveal that the key factors affecting the insulation resistance of the DCLC are the polypropylene film and the metal evaporated from the metal layer. This research is anticipated to provide a valuable reference for the further development of science and technology pertinent to the insulation resistance of DCLCs.

An algorithm for processing insulation resistance measurement data in an electrical network with an isolated neutral is proposed. The features of continuous monitoring of insulation resistance in electrical networks with semiconductor energy converters are considered. A description of a technical solution that meets the requirements of regulatory documents for mining equipment and provides an increase in the speed of the insulation resistance control procedure and protection of electrical equipment is given. The device-operation algorithm is based on the use of a periodic test signal. The test voltage source generates bipolar pulses of a special shape into an AC network. During each period of the test signal, two procedures are performed: charging the capacitance of the electrical network and directly measuring the leakage current in the steady-state mode for the measuring current. Based on the results of leakage current measurements at positive and negative test voltage values, the insulation resistance that is used in the protective disconnection circuit is determined. The decrease in the measurement error is provided by interference compensation during algebraic summation of signals proportional to the leakage current, but is shifted in time by half the period of the test signal. The insulation resistance is calculated by averaging the calculated insulation resistance value over a sliding interval equal to the voltage period of the monitored network. The signal averaged over a sliding interval is continuous; therefore, the measurement result is also formed continuously. The delay in determining when the insulation resistance drops is approximately half the period of the test voltage. Continuous monitoring of insulation resistance in dual-current electrical installations is the basis for safe operation of personnel and equipment. Results of modeling the operation of the insulation resistance control device in an electrical network with thyristor rectifiers are presented. [ABSTRACT FROM AUTHOR]

• A/B ratios impact barium titanate's dielectric properties. • A/B ratio of 1.002 enhances resistivity and insulation. • Oxygen vacancy and Ti3+/Ti4+ ratios vary with A/B. • Study aids in improving MLCC reliability and performance. The effect of the A/B ratio on the dielectric properties and insulation resistance of barium titanate (BaTiO 3) sintered in a reducing atmosphere was investigated in this study. The increased demand for high capacitance, miniaturized, and reliable base metal electrode multilayer ceramic capacitors (BME MLCCs) has emphasized improving insulation properties. This study added Y 2 O 3 , MgO, Mn 2 O 3 , and SiO 2 to tailor the barium titanate properties. We investigated how changes in the A/B ratio affect the microstructure, defect chemistry, and Y3+ ion occupation in BaTiO 3 , affecting dielectric properties and insulation resistance. It was observed that the activation energies for grain and grain boundary conductivity are dominated by oxygen vacancy and (V Ba ″ − V O · · ) defect pair, respectively. The Ti3+ and oxygen vacancy concentrations were directly proportional to the room and high-temperature resistivities, respectively. The sample with an A/B ratio of 1.002 had the lowest oxygen vacancy and Ti3+ ratio, resulting in a higher resistance and lower thermally stimulated depolarization current (TSDC). Thermally stimulated depolarization current results of the samples with varying A/B ratios. [Display omitted] [ABSTRACT FROM AUTHOR]

This article investigates the effects of operating current, soil properties, and UV ageing on the insulation resistance of cables used in the photovoltaic (PV) industry. Based on standardized experimental tests, the temperature-dependent conductivity was measured, and therefore the temperature–conductivity relationship for each cable type is extracted. Using the Arrhenius equation, a mathematical model was developed, which provided the basis for subsequent simulations of the cable insulation resistance based on the thermal properties of the insulation material, surrounding soil, and the current flowing through the conductor. The simulation provided insights into the dynamic changes of the insulation resistance based on the operating parameters. Moreover, the experimental UV ageing of cables used in the PV industry provided important insights regarding the downgrading of the insulation resistance upon prolonged exposure to the sun. [ABSTRACT FROM AUTHOR]

• Characterization of insulating materials plays a major role in the research where composite materials are used for the magnet insulation. • Proper identification tools is must to detect the signs of insulation degradation as the risk of insulation failure in a magnetic coil increases with time and operation. • The impurities and salt deposited inside the copper tubes can be removed by the DM water circulation and its effect is different during different humidity level. The realisation of tokamak and equivalent devices which operate on the principle of magnetic confinement is dependent on the successful design, development and subsequent reliable operation of the magnet coils. There is a high reliance of physics experiments on the magnetic field parameters which finally depends upon the magnet cost. Almost every time, main focus is laid on characterizing the magnet's performance and insulation properties and erosion rates of the magnets are rarely measured. The main objective of this work is to identify existing problems in coil insulations under various situations and to propose strategies to condition them. This has resulted in a better understanding of operating conditions for coil insulation in ADITYA-U tokamak. The work is based on dealing with the nature of underlying physical assumptions and the sufficiency of experimental observations. The detailed analysis of scenarios provides insight into the dominant humidity responsible for a drop in insulation resistance in ADITYA-U tokamak. A detailed understanding of the varying humidity conditions imposed on magnet insulators and their response has been presented in great detail. [ABSTRACT FROM AUTHOR]

Over operation time, there are a number of internal and external factors that change the characteristics of dielectric materials that are part of the electrical equipment. In areas with high pollution, an important requirement is the acidic chemical compounds in the soil in which the power cables are laid, which penetrate the insulation by infiltration, resulting in changes in the parameters of electrical insulation and causing a decrease in operating time. The paper is focused on the analysis, through a series of experimental determinations, of the effects of stresses to which the power cables laid in acidic environments are subjected, by simulating the operating conditions in the laboratory, obtaining concrete results. It also describes the direct current test installation used in the laboratory and presents the two stages of testing the cable sample inserted in the electrolyte, the first being a stage of accelerating the degradation of the insulation by supplying higher voltages to require insulation, and the second stage being the testing in the absence of the electric field, under the direct action of the chemical compounds from the installation tank. Given that in alternating current, the electric field causes an additional heating of the dielectric due to energy losses by electric polarization, the test is performed in direct current, precisely to be able to monitor the variation of insulation resistance in relation to temperature and losses through conduction currents, as a result of the Joule–Lenz effect and not as a result of the dielectric polarization process. At the same time, the power of the direct current source used is lower compared to that of an alternative current test source and does not contribute to the generation of electrical discharges during testing. [ABSTRACT FROM AUTHOR]

ABSTRACT: Background: Electrical socket outlets are used continuously until a failure occurs because they have no indication of manufacturing date or exchange specifications. For this reason, 659 electrical fires related to electrical socket outlets broke out in the Republic of Korea at 2018 only, an increase year on year. To reduce electrical fires from electrical socket outlets, it is necessary to perform an accelerated test and analyze the thermal, insulation resistance, and material properties of electrical socket outlets by installation years. Methods: Thermal characteristics were investigated by measured the temperature increase of electrical socket outlets classified according to year with variation of the current level. Insulation resistance characteristics was measured according to temperature for an electrical socket outlets by their years of use. Finally, to investigate the thermal and insulation resistance characteristics in relation to outlet aging, this study analyzed electrical socket outlets’ conductor surface and content, insulator weight, and thermal deformation temperature. Results: Analysis showed, regarding the thermal characteristics, that electrical socket outlet temperature rose when the current value increased. Moreover, the longer the time that had elapsed since an accelerated test and installation, the higher the electrical socket outlet temperature was. With respect to the insulation resistance properties, the accelerated test (30 years) showed that insulation resistance decreased from 110 °C. In relation to the installation year (30 years), insulation resistance decreased from 70 °C, which is as much as 40 °C lower than the result found by the accelerated test. Regarding the material properties, the longer the elapsed time since installation, the rougher the surface of conductor contact point was, and cracks increased. Conclusion: The 30-year-old electrical socket outlet exceeded the allowable temperature which is 65 °C of the electrical contacts at 10 A, and the insulation resistance began to decrease at 70 °C. It is necessary to manage electrical socket outlets that have been installed for a long time.

The objectives of this paper are to measure the resistance of insulation and contact, simultaneously the CB’s contact when opened/closed operations; and the quality of SF6 gas. Research of method, namely measure the resistance, simultaneously the CB’s contact, and quality of gas to be compared into the standard. Research results in the form of (a) insulation resistance is 97,000 MΩ and contact resistance was measured in ranging of 33 to 35 Ω, (b) simultaneously the CB’s contact was measured in ranging of 1.7 to 4.8 milliseconds, and (c) the quality of gas which includes several parameters, namely (i) gas pressure was measured 7.4 bar, (ii) impurity was measured in ranging of 98.4 to 98.9%, (iii) the dew point was measured in ranging of -41 to -45 0C and moisture content was measured in ranging of 80 to 104, and (iv) the value of products decomposition was measured in ranging of 33 to 100. Based on these results concluded, that the overall of part of circuit breaker with mediated by gas of SF6 is still a very viable when re-operated.

PVC is widely used as an electrical insulation for low-voltage indoor wiring and underground cabling. These cables are attacked by contaminants and chemicals present in the soil. The elevated temperatures and pressures inside the soil also adds up to stresses and deteriorates their insulations and sheaths and this eventually goes on damaging the conductors. So their performance in the contaminated service environment should be investigated considering extreme conditions in order to predict and ensure reliable service life. In this research 4 different PVC cable samples (2 core 10 mm2, 4 core 10 mm2, 4 core 120 mm2 and 4 core 240 mm2) were subjected to mechanical (via small punches), thermal, chemical and electrical stress over each core of the cable. Electrical stress was applied with 1 kV AC transformer. These samples were aged for 1000 hours under International Electrotechnical Commission (IEC) 1000 hours multistress aging conditions. Visual inspection and electrical characterization was done by Breakdown Voltage and Insulation Resistance Test for insulation and sheath at different intervals to investigate early stage degradation and reduction in lifetime. The results were compared with the characterizations already reported in the literature. Physical appearance and chemical degradations were apparent from the visual inspection of end aged samples. Quantitatively the results also indicated the continual decline in the breakdown voltage and insulation resistance over the aging time. Our findings inferred that the depreciation in quality of PVC cables (insulations and sheaths) is likely due to the chemical stresses which also instigates all other stresses

Gas discharge tube (GDT) breaks down discharge with surge overvoltage during long-term use. Notably, there is a risk of short-circuit failure due to the drop in insulation resistance after a certain number of discharges, which might be mainly caused by cumulative discharge. This article builds a cumulative discharge experiment platform to analyze the failure mechanism, performed the GDT whole life cycle cumulative discharge experiment and focused on the change law of its insulation resistance and breakdown voltage. For samples that are short-circuited, X-ray observation and vibration testing perpendicular to the GDT axis are conducted to examine the internal micro-morphology without damaging their external structure. The GDT is opened and its internal structure and material properties of the GDT cavity are compared and analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) methods. The results indicated that the insulation resistance of GDT continuously decreased by several orders of magnitude in the last 10% of the life cycle, and the insulation resistance before failure is generally less than 1 $\text{k}\Omega $. Through X-ray observation of the short-circuit failure sample, two different abnormal growth phenomena in the cavity are found, including flocs between the electrodes and deposits on the tube wall. Further analysis and experiments demonstrated that the flocs between the electrodes and the deposits on the tube wall are the primary factors causing the degradation of GDT insulation performance. The formation mechanism of the two short-circuit modes is explained by the difference in the splash angle and mode of metal particles of different sizes on the electrode surface. [ABSTRACT FROM AUTHOR]

The dielectric properties of insulating liquids are very important for their application as insulation and coolant in electrical devices like transformers. It is important to monitor the health condition of transformers for uninterrupted and economical power supply. For this purpose, the simple insulating materials like pressboard and mineral oils are used. This paper presents an eco-friendly alternative to mineral oil in the form of the synthetic ester oil-based nanofluids. This paper aims to present the effect of nanoparticles on the dielectric dissipation factor and electrical resistivity of ester-based oil. In this paper, we are testing synthetic ester oils for DC resistivity and dielectric dissipation factor (Tan-delta) at different temperatures starting from room temperature up to 80°C by incorporating nanoparticles with 0.02 weight% concentration. Nanoparticles used in this study are Fe2O3, TiO2 and Al2O3. Synthetic ester oil is used as the base oil for testing. These oils are manufactured from raw materials that are basically formed by combining acids and alcohols. The heating chamber is used to heat the oil for different temperatures. Insulation resistance (IR) tester and oil dissipation factor meter are used to determine DC resistivity and dielectric dissipation factor (DDF) of simple synthetic ester oil and nano oil respectively. This paper presents the effect of nanoparticles and temperature on dielectric properties of synthetic ester-based oils. [ABSTRACT FROM AUTHOR]

Addressing the critical need for enhanced safety in the burgeoning electric vehicle market, this study presents a novel insulation detection method based on the Extended Kalman Filter (EKF) algorithm. To resolve the conflict between the response speed and detection accuracy of the insulation detection system caused by Y-capacitors, the Levenberg–Marquardt (L-M) algorithm is employed to effectively estimate the parameters of the feedback voltage model developed for an unbalanced electrical bridge. The state equation of the insulation testing system has been constructed, and the EKF algorithm is applied innovatively to monitor insulation resistance and Y-capacitance, demonstrating superior anti-interference capabilities. Simulation experiments have underscored the significant contributions of the L-M algorithm in expanding the detection scope of the system. Bench tests confirmed the ability of the approach to monitor changes in insulation resistance and Y-capacitance rapidly and accurately. Under normal conditions, the maximum relative error for insulation resistance measurement is 1.56%, with a response time of 1.5 s. • Identifying insulation system parameters via Levenberg-Marquardt algorithm. • Use extended Kalman filter for insulation resistance monitoring. • Simulations and experiments validate proposed approach efficacy. [ABSTRACT FROM AUTHOR]

Au/Pt thermocouples are considered as an alternative to High Temperature Platinum Resistance Thermometers and are one of the prime candidates to replace them as the interpolating instrument of the International Temperature Scale of 1990 (ITS-90) in the temperature range between about 660 °C and 962 °C. This work presents the results of investigation of two Au/Pt thermocouples that used exclusively quartz glass (SiO2) as insulation material. Measurements in fixed points of Zn, Al, and Ag were realized on these thermocouples as well with interchanged inner insulation made of high purity aluminium oxide (Al2O3). The conducted experiments tested the performance of Au/Pt thermocouples with the use of different insulation materials. The measured electromotive forces were found to be sensitive to the replacement of the quartz glass by aluminium oxide as an insulation material of the Au/Pt thermocouples. This change of insulation has resulted in a temperature increase up to about 0.5 K measured at the freezing point of silver. The decreasing insulation resistance of quartz glass at higher temperatures is believed to be the source of thermoelectric instability.

The paper presents an approach to testing old cable, damaged during atmospheric discharges. A description of the cable is given and a series of tests in the field is proposed in order to evaluate the cable insulation condition. First, the results of the insulation resistance and capacity obtained by the DC test voltage are given and explained. The results of the insulation resistance and capacitance tests as well as the values of the dielectric loss factor tgδ, obtained at sine wave voltage, frequencies of 0.1Hz (VLF), were then interpreted. The example shows a good value of tgδ as well as a breakthrough in cable insulation, and the characteristic changes in the measured cable parameters during the test are highlighted. The advantage of estimating the insulation state by measuring the dielectric loss factor method is emphasized. Finally, the importance of systematic data collection for a particular cable type and the ability to determine the residual life with minimum insulation stress are highlighted.

Ultra-high temperature thin-film sensors（ UTTSs ）have drawn enormous attention due to their wide application prospect in multiple physical parameters monitoring in harsh environment. As an important part of UTTSs , the insulation film between workpiece and sensors plays a crucial role to ensure the accuracy of UTTS s. High insulation resistance (IR) is essential for the reliability improvement of the UTTSs and the reduction of their testing error. However, the defects in the insulation film will form the conductive path between the sensors and their mounting surface at high temperature, leading to a rapid IR drop and stability deterioration of the insulation film. In this work, 10 μm thick alumina film was prepared with suspension made out of alumina gel and alumina nano-powder using layer-by-layer electrohydrodynamic jet (E-jet) deposition (LLED). By adopting this technique, the process defects in one layer can be remedied in situ by the next deposition layer. The prepared film shows satisfactory insulation performance at elevated temperature, and IR of the film can reach 80 MΩ, 3 MΩ and 38 kΩ at 500 °C, 800 °C and 1200 °C, respectively. The thickness-normalized IR of the alumina film at 800 °C in this work is at least 7.8 times that obtained by other methods reported in the literatures. Moreover, after subjected to three thermal cycles from room temperature to 1200 °C, the IR of the film can still remain at 14 kΩ. The high performance of the alumina insulation film in this work can be attributed to the effective reduction of the minor defects in the LLED deposition process. [ABSTRACT FROM AUTHOR]

Multilayer piezoelectric ceramics must be sintered in a reducing atmosphere, preventing oxidation of the inner base metal. Plate-like textured (Ba, Ca)(Ti, Sn, Hf)O 3 ceramics with a <001> preferred orientation were successfully developed at a low oxygen partial pressure (PO 2 :10−8 atm) using a BaTiO 3 (BT) template with sintering temperatures < 1300 °C, which is beneficial for multilayer applications using base metal co-firing with ceramics. When adding the 3 wt% BT template, the proposed samples had a Lottgering factor of 84 %, piezoelectric coefficients d 33 = 324 pC/N, -d 31 = 122 (pC/N), and Q m = 452, and the strain values increased from 0.07 % for the randomly oriented ceramics to 0.115 % at 20 kV/cm for the textured ceramics, confirming that the texturing behavior assisted the grain growth and improved both the soft and hard behaviors and insulation resistance of the proposed lead-free ceramics. These findings make a significant contribution to the production of high-power piezoelectric components. [ABSTRACT FROM AUTHOR]

Over operation time, there are a number of internal and external factors that change the characteristics of dielectric materials that are part of the electrical equipment. In areas with high pollution, an important requirement is the acidic chemical compounds in the soil in which the power cables are laid, which penetrate the insulation by infiltration, resulting in changes in the parameters of electrical insulation and causing a decrease in operating time. The paper is focused on the analysis, through a series of experimental determinations, of the effects of stresses to which the power cables laid in acidic environments are subjected, by simulating the operating conditions in the laboratory, obtaining concrete results. It also describes the direct current test installation used in the laboratory and presents the two stages of testing the cable sample inserted in the electrolyte, the first being a stage of accelerating the degradation of the insulation by supplying higher voltages to require insulation, and the second stage being the testing in the absence of the electric field, under the direct action of the chemical compounds from the installation tank. Given that in alternating current, the electric field causes an additional heating of the dielectric due to energy losses by electric polarization, the test is performed in direct current, precisely to be able to monitor the variation of insulation resistance in relation to temperature and losses through conduction currents, as a result of the Joule–Lenz effect and not as a result of the dielectric polarization process. At the same time, the power of the direct current source used is lower compared to that of an alternative current test source and does not contribute to the generation of electrical discharges during testing.

This paper presents an improved approach to testing the condition of cables in terms of further exploitation. The advantages and disadvantages of using DC and VLF test voltages are noted. A description of two damaged electric power cables in a city is given. The sequence of a realistic possible set of tests is proposed in order to assess the condition of cable insulation. Firstly, the results of the isolation resistance were explained. The results of the testing of capacitance and factor of dielectric losses at the AC 50Hz test voltage are then evaluated. At the end, insulation tests are performed with high DC voltage according to the standard. After switching on the cables, a thermographic test is performed and examples of observed irregularities are shown. In conclusion, the need for simultaneous application of several different test methods and the systematic collection of data on cable insulation is emphasized.

A measuring instrument is used to measure the insulation resistance of a cable system at a railway control centre. Moreover, online weather data is available as the source of data such as the relative humidity. A data-driven technology can be used for signal detection, signal estimation and signal forecasting. The meaningful characteristics of the data can be extracted by an algorithm so that a relationship is established between the insulation resistance of the cable and the relative humidity. In this way, the remaining lifetime of a cable can be predicted based on the previously observed values. [ABSTRACT FROM AUTHOR]

• Acceleration of post-LOCA is adequate if meeting certain conditions. • Multi-scale approach using non-destructive electrical measurements during post-LOCA. • Comparison of different non-destructive diagnostic techniques. Cables important to safety used in nuclear power plants are required to withstand environmental, operational and system conditions to which they are exposed during their design life. This may include harsh conditions resulting from a design basis event (DBE), such as a Loss-of-Coolant Accident (LOCA). The testing procedure includes accelerated thermal and ionizing radiation ageing which brings the tested samples to their end-of-life condition. Accelerated pre-ageing is then followed by accident simulation (LOCA test). The latter part of accident simulation (post-LOCA), which may take up to 1 year, is commonly accelerated based on the Arrhenius approach, however the adequacy of this approach remains a topic of ongoing discussion, lacking a clear scientific or engineering consensus. While numerous works have focused on testing various conditions during accidental and post-accidental conditions in nuclear power plants, there is notable absence of direct assessment of acceleration effects. The aim of this work was to assess the effects of accelerating post-accident conditions on electrical cables using non-destructive electrical measurements. The cables were subjected to thermal and radiation pre-ageing, LOCA test, and then were divided into two groups for post-LOCA tests: one group was tested for one year in non-accelerated post-accident conditions, while the other was accelerated using the Arrhenius approach. Diagnostic methods, including insulation resistance, capacitance, voltage withstand tests, and high-frequency parameters such as attenuation, characteristic impedance, and relative permittivity, were employed for comparing sample conditions. Results from both accelerated and non-accelerated post-LOCA simulations were consistent, indicating that the acceleration was adequate. [ABSTRACT FROM AUTHOR]

• Magnetic coils are susceptible to periodic surges created during circuit breaker operations which result in severe stress across portions of insulation. • Coil insulation failure is hastened by different mechanisms i.e., voltage surge-related rupture, partial discharge deterioration and ageing resulting from thermal and mechanical stresses. • Impulse voltage test realises the operational condition of high magnitude, low duration voltage spike during the instant switching or fault operation on the insulation of any electrical system. The electromagnetic coils form one of the main component in any electrical system and its insulation is one of the crucial element towards successful operation at rated parameters. Insulation system is designed to be highly reliable while taking coil ageing and deviation in the operation settings into consideration. Still, degradation of the insulation is often observed even at a voltage value lower than the designed value. Mainly, high voltage transients severely damages the insulation system depending upon its magnitude and occurrence site which sometimes result in its premature failure. Therefore, insulation strength of the magnets are tested periodically at various stages of coil fabrication, installation and during its operation life at ratings close to the designed parameters. Out of different electrical tests, impulse voltage test realizes the operational condition of high magnitude, low duration voltage spike during the instant switching or fault operation on the insulation system. A successful impulse voltage test confirms the insulation strength towards the safe operation of high voltage operation. An impulse voltage test on the magnetic coil of ADITYA-U tokamak is performed under different operating conditions to investigate the probable cause and severity of deviation in the periodic insulation behaviour. A detailed study of water tree dynamics is examined in this work which has helped towards maintaining the operational life of the magnetic coil in ADITYA-U tokamak. Currently, understanding of water tree in OT_1 coil insulation is limited to interpretation from the experimental measurements which is supported by available theories. Therefore, experiences summarised during the heat conditioning of coil insulation in ADITYA-U will improve the understanding of the complex tree nature and the conditions that support its existence. [ABSTRACT FROM AUTHOR]

Introduction. Electrical insulation systems make up about 0.03 % of the traction electric machines (TEM) mass, but they are of exceptional importance and affect the design capabilities and manufacturing techniques of electric machines, ultimately - on their specific weight and overall dimensions, on the reliability and durability of the TEM. Purpose. The monitoring of the stability of the manufacturing process of electrical insulating systems of the TEM based on the insulation resistance measurements. Methodology. The analysis of the manufacturing process is carried out for three versions of the case of insulation of the magnetic system of the DC traction electric motor. Practical value. Construction and analysis of special graphs (charts) of individual values and cumulative sums of insulation resistance, sliding range MR allow to find out whether the technological process of manufacturing electric insulating systems of traction electric machines is in a statistically controllable state.

A bismuth oxide-based multicomponent glass system, xH3BO3-yBi2O3-(1-x-y-δ)MO-dδrare earth oxides (REOs) with MO 5 TiO2, BaO, ZnO, Fe2O3, etc., and lanthanum series-based REOs, for making downhole high-pressure and high-temperature electrical feedthrough package has been developed using hightemperature melt-quenching and sintering technologies. By properly controlling phase structures in material-manufacturing processes, the obtained sealing materials have shown moistureresistant properties in their monoclinic and tetragonal mixed phase structures but strongly hydrophobic properties in their covalent bond tetragonal phase. Sealed electrical feedthrough packages have been evaluated under boiling water immersion and 200°C/30,000 PSI water-fluid-simulated downhole harsh environments. The post electrical insulation measurement has demonstrated to be greater than 1.0 × 1014 Ω electrical resistance. This article will show that such a high-bonding strength and high-insulation strength sealing material could be used to seal electrical feedthroughs and connectors for 300°C/30,000 PSI downhole and subsea wireline, logging while drilling, and measurement while drilling tools' signal, data, and electrical power transmissions. [ABSTRACT FROM AUTHOR]

With the increasing usage of cross‐linked polyethylene (XLPE) power cables, it is more and more important to grasp and manage their insulation status. Nowadays, the distribution cables in urban area are of huge numbers, so it is impossible to carry out the preventive test for every cable. Therefore, it is very helpful to determine cables' testing urgency in a scientific way. Meanwhile, the main cable diagnosis methods in China are insulation resistance and withstanding voltage test, but they are difficult to quantitatively determine cable insulation status. Aiming at solving above challenges, according to the cable fault records in recent years, fuzzy evaluation analysis combining with mutual information is utilised to determine the insulation testing urgency (ITU) based on cable information including service year, laying way, load type, and length. At the same time, frequency domain spectroscopy (FDS) is introduced to diagnose the on‐site cable insulation status quantitatively. Its characteristic parameters, including instantaneous electric susceptibility, DC conductivity, and hopping conductivity, are extracted by improved Havriliak–Negami (H‐N) model and studied to analyse the changing trend before and after cable deterioration. The results show that the lower ITU is, the higher testing urgency is. ITU also has negative correlation with FDS characteristic parameters. [ABSTRACT FROM AUTHOR]

Theoretical and experimental studies were conducted to investigate the impact of the cable capacitance during measurements of insulation resistance on the fast response time of a resistance-to-voltage converter. From a comparison of the results of simulation with the data obtained during the experiments, it was determined that the dependence characteristics of the settling time of resistance under measurement on the capacitance are identical to the analogous characteristics of electronic components of the resistance-to-voltage converter. It was experimentally proven that using T-shaped feedback in the resistance-to-voltage converter during the cable insulation resistance measurements reduces the settling time of the data by 1–3 times in comparison with a classical feedback system. Furthermore, when using the optimal parameters, the settling time of the resistance-to-voltage converter with T-shaped feedback depends to a lesser degree on the capacitance of the object under control.

Purpose. In the paper there are described methods of two and three voltmeter readouts for insulation resistance periodic measurement in live DC and AC/DC IT networks. A new measuring method for AC/DC networks is proposed. Application of a novel algorithm for shortening of measurement cycle is explained. Methodology. All methods of two and three voltmeter readouts consist in connection of a resistor and measurement of mean value of network’s fixed point-to-ground voltages. Results. A new algorithm implemented in KDZ-3 device enables determination of steady-state voltage of a DC network’s pole much faster than in other exploited systems. Originality. In author’s modification of two voltmeter readouts method, line-to-ground voltage mean value is measured at AC side of AC/DC network. This innovation has not been applied for implementation of periodic insulation monitoring in AC/DC IT networks yet. Practical value. The use of author’s innovation will allow to execute measurements at AC side of AC/DC IT networks which might be necessary if rectifier’s output circuits are unavailable. Shortening of measurement cycle duration of two or three voltmeter readouts method’s is of great importance in networks with high capacitance.

Purpose. The article deals with the insulation resistance of the track circuit as one of the parameters that affect the operating performance of the railway transport. To reduce the influence of the insulation resistance on the operation modes of the track circuits and the performance indicators of railway transport it is assumed to study the influence of crushed stone treatment on the value of dielectric permeability of the ballast bed. Methodology. The influence of material type for the surface treatment of crushed stone on the value of the dielectric permeability was assessed on the basis of the physical nature determination of the relative dielectric permeability. Determination of the relative dielectric permeability of granular media can only be indirect, as a consequence of incomplete adjoining of crushed stone grains and uncertainty of the pore volume. Thus, the calculations were performed by comparing the measured capacity for a medium with the known with measured medium capacity, for which it is necessary to define. That is, the more the measured capacity is changed, the more changes the dielectric permeability of the medium. Findings. Sleepers and ballast significantly change their electrical conductivity depending on the presence of moisture, ambient temperature changes, the presence of pollutants and other factors. The article analyzes the existing models to describe the dielectric properties of such systems. It has been established that coating the crushed stone ballast with organic substances influences the value of its relative dielectric permeability. The greatest effect of reducing this value is observed for the coatings based on rosin mixture and silicone. Originality. Authors proposed original method of dielectric properties increase of the permanent way by grains’ coating with nonwettable substances, on the surface of which is not formed a water film. Practical value. The article shows the possibility of minimizing the negative influence of reducing the isolation with maximum its elimination. It is proposed the solution of actual problem by eliminating the influence of insulation resistance on the modes of track circuits operation, which will eliminate the part of causes of the failure of signaling devices and reduce the number of cases of «false business».

Purpose. In the paper there are described few systems of insulation resistance continuous measurement using an imposed DC test signal delivered by diode rectifiers. Drawbacks of this technique are pointed out and ways of these shortcomings removal are proposed. Methodology. An improved version of measuring circuit based on a single-phase diode rectifier is presented. Application of logometric measuring devices is suggested. Results. A new insulation resistance continuous measuring system is insensitive to network voltages variation and asymmetry. Modified circuit enables also implementation of a simple device for alarming the monitored network’s insulation deterioration and/or earth-fault protection. Originality. Formulas describing performance of diode rectifiers under asymmetrical supply have not been available so far. Both innovations (i.e. single-phase diode rectifier and logometric meter) have not been applied widely for implementation of continuous insulation monitoring in live AC IT networks. Practical value. Use of both innovations will allow to eliminate unrequired dependence of measurement results on variable network voltages as well as their possible asymmetry. Exploitation of diode rectifier circuits for earth fault location is also possible.

This study evaluated the insulation resistance characteristics of TFR-8 (Tray Frame Retardant power cable for fire service) and VCTF (Light PVC Sheathed Circular Cord) cables under external flame, over-current, and accelerated degradation tests. In the accelerated degradation test of the cable, aging times of 10, 20, 30, and 40 years were tested according to a temperature derived using the Arrhenius equation. The insulation resistance of the TFR-8 cables was reduced from a maximum of 7.5 T ohm to 0.008 T ohm during the flame contact and recovered to its original state after cooling. However, dielectric breakdown occurred in the VCTF cable during flame contact and the cable did not return to its original state, even after cooling. In the forced convection oven test, the insulation resistance of the cable was reduced at 160 °C, whereas the insulation resistance of the cable was reduced at 125 °C in the over-current test. This result implied that the over-current had a greater impact than did heat applied externally on the degradation of the cable insulator. In the accelerated degradation tests from 10–30 years, the TFR-8 cable did not show any reduction in insulation resistance at room temperature. However, after an induced aging time of 40 years, the cable showed a rapid reduction in insulation resistance at room temperature.

Introduction. The moral and physical deterioration of medium voltage power cables with phase and zone paper-impregnated insulation requires implementation of quality systems and reliable nondestructive electric diagnostic. Informative indicator of the insulation is the time decay curve of the charging current. It reflects the processes of accumulation of space charges (absorption). The measurements are carried out the 15th since the second direct voltage supply, then – on the 30th and the second on the 60th second. The ratio of the parameters measured in these times gives the dimensionless criteria – absorption coefficients. Three measurements are made at different times, provide a more complete picture of the state of insulation than the measurement of the value of steady leakage (conduction-through), adopted in conventional prevention trials. Purpose. Research and testing methods of diagnostics of power cables with paper-impregnated insulation by absorption and phase characteristics of the belt insulation based on the total measurements. Methodology. A procedure for determining the individual characteristics of phase and zone paper-impregnated insulation based realized on the use of the equivalent circuit of a three-core cable in the metal shell and solved of an over determined system of linear algebraic equations by least squares. Results. The proposed method allows determining the absorption characteristics of the individual phase and zone insulation medium voltage power cables in the overall metal shell at a direct voltage. Individual characteristics reflect the characteristics of cables and allow a greater degree to assess the degree of aging of each of the components of paper-impregnated insulation. Originality. Regardless of the cable connection diagrams probing electric field grabs as the phase, and zone insulation. The cumulative nature of the measurement leads to the fact that the differences in the properties of insulation components are smoothed: the aggregate results of the measurements do not differ for the different schemes of the same type. The individual characteristics of isolation, defined on the basis of the proposed method are more differences than total, indicating that non-symmetrical modes of operation of the cable. Practical value. The values of individual characteristics power cables 6 kV are 3 times more total, because of what their direct measurement may be a problem. The total resistance of several insulation spaces connected in parallel, behind the individual. Smaller values of insulation resistance are measured more easily, especially on short samples cables.

The relevance of the study is conditioned by the need to determine the state and residual life duration of high-voltage cable lines to identify faulty and maintainable cables. The aim of the article is to determine a reliable scientifically grounded criterion for assessment of insulation characteristics of the cables in use and to perform a comparative analysis of the results obtained by the traditional method of diagnosing insulation with the results of a new method of assessment by the return voltage. In this regard, the article deals with the issues related to the testing of cables having oil-impregnated paper insulation, as well as with the issue of switching from planned replacement of cables to assessment of their actual state and period of residual life. The authors propose to use the method of examining the cables by the return voltage using the device for testing electrical insulation "UDEI-1" developed at the department of Electrification and Automation of the Nizhny Novgorod State University of Engineering and Economics. The article presents the results of measuring the return voltage of three cables that operated under different conditions. The cables had different technical state. The analysis of the estimation of the residual life of cables by the return voltage was carried out using such criteria as the PIRV polarization index, the LIRV electrical conductivity index, and the P-factor. The P-factor is the physical criterion demonstrating the aging of paper-oil insulation by the shape of the return voltage curve. It represents such characteristics of insulation aging as moistening. To compare the results of testing the cables by the return voltage with the conventional methods of diagnostics and to determine the actual technical condition of power cables, the authors applied the method of spatiotemporal reflectometry and the method of measuring insulation resistance with the determination of such indicators of state as insulation resistance normalized per one kilometer, absorption coefficient, and polarization index. The results of this article confirm that the return voltage gives a qualitative assessment of the state and degree of aging of cables with impregnated paper insulation. The authors proposed a new system for evaluation of cable condition by weighting coefficients. In this approach, the determination of residual life of cables with impregnated paper insulation is based on the values of the return voltage. Application of the new system gives opportunity to improve reliability of the power lines. Recommendations for the further operation of the studied cables are given. The materials of the article are of practical value for carrying out complex assessment of the technical condition of power cables by the return voltage and can be useful for drawing up a schedule for replacement or repair of cable lines depending on their actual state. [ABSTRACT FROM AUTHOR]

Premature or unplanned removal of power transformers from operation can cause significant losses to energy suppliers and consumers. Therefore, knowing the estimated lifetime and, especially, consumed and remaining lifetimes of transformer insulation is of particular importance. This paper presents the results of a study on the use of transformer winding insulating resistance as a diagnostic factor for the determination of the aM,D and bM,D parameters of the lifetimes lines for the Montsinger and Dakin ageing models. The methods to determine these parameters are presented, both by accelerated laboratory tests and by measuring the windings insulating resistance of the transformers in operation, the method of calculating Dakin line parameters based on the Montsinger parameters (and vice versa) and the calculation of these parameters based on the insulation resistance values and the temperature variation curve of the insulation. Finally, it is shown that the parameters aM,D and bM,D change their values during transformers operation and their numerical calculation is presented for 5 transformers in operation. [ABSTRACT FROM AUTHOR]

Due to the energy crisis and environmental pollution, electric vehicles have become more and more popular. Compared to traditional fuel vehicles, the electric vehicles are integrated with more high-voltage components, which have potential security risks of insulation. The insulation resistance between the chassis and the direct current bus of the battery pack is easily affected by factors such as temperature, humidity and vibration. In order to ensure the safe and reliable operation of the electric vehicles, it is necessary to detect the insulation resistance of the battery pack. This paper proposes an insulation detection scheme based on low-frequency signal injection method. Considering the insulation detector which can be easily affected by noises, the algorithm based on Kalman filter is proposed. Moreover, the battery pack is always in the states of charging and discharging during driving, which will lead to frequent changes in the voltage of the battery pack and affect the estimation accuracy of insulation detector. Therefore the recursive least squares algorithm is adopted to solve the problem that the detection results of insulation detector mutate with the voltage of the battery pack. The performance of the proposed method is verified by dynamic and static experiments. [ABSTRACT FROM AUTHOR]