Insulation Of High Voltage Equipment Research Articles

Up-gradation of the dielectric, physical & chemical properties of cottonseed-based, non-edible green nanofluids as sustainable alternatives for high-voltage equipment's insulation fluids

The use of natural ester oils as electrically insulating fluids has gained significant attention from industries and electrical utilities as they aim to replace traditional mineral oils. However, most natural ester oils are derived from edible products, which has the potential to contribute to the food crisis. Therefore, nonedible green nanofluids made from cottonseed oil (CSO) have been targeted as a keen solution to this issue. However, Al2O3, TiO2, Fe2O3, SiO2, and graphene nanoparticles at (0.025, 0.05, and 0.075 wt/vol%) were used as additives, along with surfactant Olic Ac-id and Ethanol (1:5) due to their promising impact on the dielectric and thermal properties of the nanofluid. The nanofluid synthesis process was practically conducted in HV & Chemical Laboratories using one-step and two-step methods, and their breakdown voltage results and chemical properties (e.g., fire point, flash point, cloud point, pour point, viscosity, acidity, moisture content, resistivity, and dissipation factor) were compared. The physical mechanisms underlying these properties were also analyzed and tested. For the validation of the proposed vegetable oil the results have been compared with traditional mineral oil for high-voltage equipment's. The findings suggest that the proposed nonedible green nanofluids-based cottonseed oil (CSO) has a high potential to be used as electrically insulating fluids, providing a sustainable alternative to conventional mineral oils. Overall, this study provides insights into the use of non-edible green nanofluids as a solution to the potential contribution of natural ester oils to the food crisis. The findings highlight the importance of sustainable solutions in the energy industry and the need for further research in this area.

Dielectric Performance of Natural- and Synthetic-Ester-Based Nanofluids with Fullerene Nanoparticles

According to the latest research, nanofluids as a possible future substitution for high-voltage equipment insulation have the potential to enhance the heat transfer and insulation properties of their base fluids. Dielectric properties are represented by breakdown strength (AC, DC, lightning) and dielectric performance as a set of quantities including dissipation factor, permittivity, and volume resistivity. In this study, natural and synthetic esters were mixed with C60 nanoparticles. Samples were examined for dissipation factor, relative permittivity, and volume resistivity at temperatures between 25 °C and 140 °C to monitor changes in dielectric performance with rising temperature, in accordance with IEC 60247. In addition, the samples were tested for AC breakdown voltage (using mushroom-like electrodes with a gap distance of 1 mm) and evaluated using the Weibull distribution statistical method. These measurements allowed complex evaluation of the examined mixtures and the determination of optimal concentration for each ester-based nanofluid.

Very fast transient overvoltage calculation and evaluation for 500‐kV gas insulated substation power substation with double circuit and long gas insulated substation busbar

The operation of disconnectors in gas insulated substation (GIS) or power plant will produce very fast transient overvoltage (VFTO), which is considered to have serious harm to transformer longitudinal insulation and other high-voltage equipment insulation. VFTO may also lead to secondary circuit failure. In this paper, the holistic modelling of 500 kV GIS step-up substation equipment with a double circuit and long GIS busbar in a coastal power plant is established using Electromagnetic Transient Program (EMTP). The authors calculated the VFTO waveform that may be generated in different operations of the GIS substation. The authors analyze the amplitude and frequency characteristics of the VFTO waveform at lightning arresters and the entrance of transformers and find that the amplitude of VFTO at the entrance of #1 MT is less than its impulse withstand voltage. In some cases, the VFTO waveform at the entrance of #1 MT has high-frequency content with fast attenuation. The VFTO waveform generated when operating the disconnector close to the arrester will cause the arrester to act many times and count frequently in a short time.

To the Evaluation of the Insulation State Based on the Analysis of Partial Discharges

The existing partial discharge models, their diagnostic value, and application area are analyzed in the article. The models are considered from the point of view of their improvement or the possibility of creating new diagnostic methods for electrical equipment based on the characteristics of partial discharges. As an example of the implementation of a new approach to partial discharge modeling, a quasi-deterministic model is considered, which makes it possible to obtain information on the real number of cavities in the insulation of high-voltage equipment.

Partial Discharge Location Through Application of Stationary Discrete Wavelet Transform on UHF Signals

The degradation level of high voltage equipment insulation systems can be estimated from the monitoring of partial discharge (PD) activity. The radiometric method stands out as one of the most promising methods for monitoring these discharges, however, in substations, the PD signals may be susceptible to external interference and, in some cases, hide by background noise. This work presents the application of the stationary discrete wavelet transform (SDWT) over PD signals measured by bio-inspired printed monopole antennas (PMA) operating at the UHF frequency range (300-3000 MHz). In addition to the filtering from the SDWT, the use of the SDWT scaling coefficients energy is evaluated as a support tool for the location of PD. The PD signals are investigated under low signal-to-noise ratio (SNR) and; high SNR with a high pulse repetition rate. These signals are obtained from a laboratory setup composed by a discharge generating oil cell, and acquired through a bio-inspired PMA. After the application of the SDWT over the evaluated signals, together with the energy calculation using different mother wavelets, it is verified that the proposed methodology provides an efficient filtering result, being appropriate for PD detection. From the energy of SDWT scaling coefficients, it is possible to highlight the constant delays between the detection of consecutive pulses, minimally interfering over the time differences of arrival and providing better location results.

New Insulating Fluids and Diagnostic Techniques for Paper-Oil Insulated Equipment1

In 2021, the International Council on Large Electric Systems (CIGRE) will celebrate its centenary. CIGRE Sessions are traditionally held face-to-face in Paris once every even-numbered year. However, in 2020, in response to the coronavirus pandemic, the organizers of the 48th CIGRE Session decided to hold a virtual meeting for experts, specialists, engineers, and researchers from all over the world. The result was an e-session that included engaging seminars, tutorials, and discussions. At the virtual meeting, participants discussed various problems and challenges currently affecting all areas of the energy sector. Current pressing issues include the development of informative diagnostic techniques for oil-filled equipment, as well as the potential applicability of environmentally friendly biodegradable synthetic and natural esters for use as liquid insulation in high-voltage equipment. This review presents the latest research, practical solutions and reports on the experience of applying new techniques and novel liquid insulating materials. Valuable and up-to-date information in these fields is provided by experts and specialists from all over the world.

Pengukuran dan Analisis High Frequency Current Transformer Pendeteksi Partial Discharge

The lifetime of high voltage equipment is very dependent on the condition of insulation, poor insulation means the life span of high voltage equipment is getting shorter. Partial Discharge is one of the causes of deterioration of high voltage equipment insulation. The ability to know the phenomenon of partial discharge in equipment becomes very important and adds value to the maintenance of high voltage equipment. Many explanations regarding partial discharge, partial discharge is the lack of uniformity of the electric field in the isolation or dielectric media which will result in the phenomenon of Partial Discharge where this will lead to the failure of the isolation media. Partial Discharge that occurs continuously can cause damage (breakdown) on a high voltage equipment. Therefore, before a high voltage device is used, Partial Discharge detection is necessary. Partial Discharge Detection can use the Partial Discharge measurement circuit. In testing partial discharges can be tested using a sensor with various circuits including High Frequency Current Transformers (HFCT) so that this research will discuss one part of the Partial Discharge measurement circuit, the HFCT detector. Hopefully, the HFCT detector can be further developed and can be used for better partial discharge detection.

Discrete Diagnostic Model of Many High-Voltage Equipment Insulation Defects

Discrete Diagnostic Model of Many High-Voltage Equipment Insulation Defects

A Review of Techniques for RSS-Based Radiometric Partial Discharge Localization.

The lifespan assessment and maintenance planning of high-voltage power systems requires condition monitoring of all the operational equipment in a specific area. Electrical insulation of electrical apparatuses is prone to failure due to high electrical stresses, and thus it is a critical aspect that needs to be monitored. The ageing process of the electrical insulation in high voltage equipment may accelerate due to the occurrence of partial discharge (PD) that may in turn lead to catastrophic failures if the related defects are left untreated at an initial stage. Therefore, there is a requirement to monitor the PD levels so that an unexpected breakdown of high-voltage equipment is avoided. There are several ways of detecting PD, such as acoustic detection, optical detection, chemical detection, and radiometric detection. This paper focuses on reviewing techniques based on radiometric detection of PD, and more specifically, using received signal strength (RSS) for the localization of faults. This paper explores the advantages and disadvantages of radiometric techniques and presents an overview of a radiometric PD detection technique that uses a transistor reset integrator (TRI)-based wireless sensor network (WSN).

Determination of Water Content in Liquid Insulation of High-Voltage Equipment by Different Methods

Control of the formation and behavior of water in a liquid dielectric during the operation of high-voltage equipment is of paramount importance because water provokes intensive oxidation and aging of the entire oil-solid insulation system. The electrophoretic ability of water has a strong effect on the insulating properties of dielectrics inside a high-voltage apparatus, and, in general, on its uninterrupted long-term operation. Problems associated with the determination of moisture in the complex hydrocarbon matrix of transformer oil by all available methods are considered. It is shown how different states of water in transformer oil of various grades can be determined by varying the temperature in the evaporator of the chromatographic unit. Chromatographic data are compared with data obtained by conventional methods (Karl-Fischer coulometric titration, calcium-hydride method, coulometric sensor based electrolysis).

Denoising of Radio Frequency Partial Discharge Signals Using Artificial Neural Network

One of the most promising techniques for condition monitoring of high voltage equipment insulation is partial discharge (PD) measurement using radio frequency (RF) antenna. Nevertheless, the accuracy of monitoring, classification, localization, or lifetime estimation could be negatively affected due to the interferences and noises measured simultaneously and contaminate the RF signals. Therefore, to achieve high accuracy of PD assessment, exploiting the denoising algorithms is inevitable. Hence, this paper seeks to introduce a new technique to suppress white noise, the most prevalent type of noise, especially for RF signals. In the proposed method, the ability of artificial neural network (ANN) in curve fitting is applied to denoising of different types of measured RF signals emitted from PD sources including ‘crack’, ‘internal void’, in the insulator discs and ‘sharp points’ from external hardware. The processes of denoising for named signals with the proposed method are carried out, and the obtained results are compared with the outputs of a wavelet transform-based method named energy conversation-based thresholding. In all tested signals, the proposed technique showed superior denoising capability.

Control of the Antioxidant Additive (Ionol) Content in Liquid Insulation of High-Voltage Equipment in Electric Grid Companies Using Modern Instrumental Methods

The article provides an overview of the methods of quantitative analysis of an additive. The specifics occurring when determining the additive using the most common chromatographic methods are discussed. The advantage of the near-infrared (NIR) technique is shown, which offers selectivity, rapidity, low labor intensity, high sensitivity and feasibility of being used in the automated monitoring systems.

Application of UHF Sensors in Power System Equipment for Partial Discharge Detection: A Review.

Condition monitoring of an operating apparatus is essential for lifespan assessment and maintenance planning in a power system. Electrical insulation is a critical aspect to be monitored, since it is susceptible to failure under high electrical stress. To avoid unexpected breakdowns, the level of partial discharge (PD) activity should be continuously monitored because PD occurrence can accelerate the aging process of insulation in high voltage equipment and result in catastrophic failure if the associated defects are not treated at an early stage. For on-site PD detection, the ultra-high frequency (UHF) method was employed in the field and showed its effectiveness as a detection technique. The main advantage of the UHF method is its immunity to external electromagnetic interference with a high signal-to-noise ratio, which is necessary for on-site monitoring. Considering the detection process, sensors play a critical role in capturing signals from PD sources and transmitting them onto the measurement system. In this paper, UHF sensors applied in PD detection were comprehensively reviewed. In particular, for power transformers, the effects of the physical structure on UHF signals and practical applications of UHF sensors including PD localization techniques were discussed. The aim of this review was to present state-of-the-art UHF sensors in PD detection and facilitate future improvements in the UHF method.

Experimental study and modeling of partial discharge detection system

The object of research is an electrical system for detecting partial discharges in a sample of high voltage equipment insulation. To evaluate the insulation state of electrical equipment, various methods for detecting partial discharges have been developed and continue to be improved. The role of modeling, virtual experiment and virtual laboratory lessons has recently increased in all areas of engineering. At the same time, some aspects of modeling the electrical systems for partial discharges detection are practically not studied sufficiently. Modeling is an important additional kind of practical training for a further work with measuring and testing equipment in professional activity. The aim of research is determination of the possibility of using an equivalent circuit simulation model in the research and educational process as an analogue of a system for measuring the characteristics of partial discharges. To measure the characteristics of partial discharges in samples of high-voltage insulation, a special experimental test stand was assembled. The stand allows testing the physical model of insulation by applying alternating current high voltage. To visualize individual partial discharge pulses on an oscilloscope, a high-pass filter was designed and assembled that suppresses the 50 Hz main frequency voltage, and is a 4th order Butterworth filter. The oscillogram of partial discharge pulses that occur near a surface of high-voltage electrode in an insulating gap with an electrical cardboard was obtained. It has been experimentally established that partial discharge impulses of different amplitudes arise in the insulating gap with an explicit polarity effect. The experimental oscillogram was adopted as a sample, to which the oscillogram should approach in the simulation. The electrical equivalent circuit for insulation is represented by a traditional three-capacitive equivalent circuit for a dielectric with a gas cavity. As a result of the research it was established that it is possible to obtain results close to those observed in the physical experiment. The possibility of modeling partial discharges in a dielectric in the presence of two or more gas cavities is shown.

Breakdown Voltage of CF3CHCl2 gas an Alternative to SF6 Gas using HV Test and Bonding Energy Methods

For more than two decades of Sulphur Hexafluoride (SF6) gases is used as a gas insulation in high voltage equipment especially in substations. In addition to getting an advantage as an insulating gas. SF6 gas is recognized as one of the greenhouse effect gases that cause global warming. Under the Kyoto Protocol, SF6 gas is one of those gases whose use is restricted and gradually reduced to the presence of a replacement gas for SF6 gas. One of the alternative gas alternatives which have the potential of replacing SF6 gas as an insulating gas in Gas Insulated Switchgear (GIS) equipment in the substation is Dichlorotrifluoroethane (CF3CHCl2) gas. The purpose of this paper is to enable a comparison of breakdown voltage with high voltage test and method of calculating Bonding energy to Dichlorotrifluoroethane gas as substitute gas for SF6 gas. At 0.1 bar gas pressure obtained an average breakdown voltage of 18.68 kV / mm at 25oC chamber temperature and has the highest breakdown voltage at 50oC with a breakdown voltage of 19.56 kV / mm. The CF3CHCl2 gas has great potential as an insulating gas because it has more insulation ability high of SF6 gas, and is part of the gas recommended under the Kyoto Protocol. Gas CF3CHCl2 has the capacity to double the value of electronegativity greater than SF6 gas as a major requirement of gas isolation and has a value of Global Warming Potential (GWP) and Ozone Depleting lower than from SF6 gas.

Study on the Effects of Thermal Aging on Insulating Paper for High Voltage Transformer Composite with Natural Ester from Palm Oil Using Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDS)

Mineral oil is widely used as liquid insulation in high voltage equipment. Due to environmental considerations, recently natural esters have been considered as naturally friendly liquid insulation candidates for high voltage transformers. In this experiment, transformer insulation paper was subjected to get accelerated aging test with copper strip in natural ester in a hermeneutical heat-resistant glass bottle at temperatures of 120 °C and 150 °C for 336 h, 672 h and 1008 h. The experimental results of Fourier transform infrared spectroscopy (FTIR) showed that the intensity of the absorbance peak of the O–H functional group decreased with aging, while the intensity of the C–H and C=O functional group absorbance peaks have increased with aging and the intensity of the C–O functional group absorbance peak has a tendency to increase with aging. The energy dispersive X-ray spectroscopy (EDS) experimental results showed that the weight percent of the element C increased with aging and the weight percent of the element O has decreased with aging. The experimental results show a good correlation between the degree of polymerization (DP) and the weight percent of O element. This indicates that EDS may be used as a new method for estimating the DP of transformer insulation paper.

Appropriate selection of shunt compensation reactor in parallel transmission lines: A case study

Shunt reactors are widely deployed as effective compensation means against the capacitive behavior of high voltage transmission lines. Subsequent to load rejection or light load conditions, a resonance phenomenon is highly potent due to remarkable capacitive feature of these lines. Reactor failure, threatening the interior insulation of high voltage equipment connected to the line, and early aging of insulations are some of the main concerns regarding resonance voltages. To study the phenomenon, different cases including complete disconnection of the transmission line, single and double pole operation of breakers, and short circuit faults on the de-energized line are simulated with two different knee points of reactor saturation. A sensitivity analysis is also conducted considering the soil resistivity and corona phenomenon. Different solutions such as neutral reactors and resistors, complete transposition of the circuits, capacitor bank and replacing the ground disconnector switches with breakers are examined in the worst case to limit the resonance overvoltage. In contrast to previous contributions, it is shown that when the shunt compensation reactor is not appropriately determined, none of the solution methods alone can resolve the resonance phenomenon. Hence, an exact and carefully-selected compensation level is of great significance.

Investigation of partial discharge frequency dependence in distribution system cables

Partial discharges (PDs) problem in dielectrics is a major factor that indicates whether the insulation of high voltage equipment is healthy or not. Moreover, it can be considered a degradation measurement tool. The applied frequency effect on PD action becomes an essential investigation. A model is established based on Matlab and Comsol Multiphysics. The model is verified by experimental results. The simulation results are used to illustrate the frequency dependence of PD.

Statistical Analysis of Partial Discharges

In this paper, a statistical analysis method is applied to partial discharge (PD) measurements for the quality assessment of electrical insulation in high-voltage equipment. The rod plane electrode system in magnetic field and non-magnetic field is selected as test environment. This data helps to showing scattering and concentration of values. In this study, the partial discharge values of electrode system under magnetic field is higher and more scattering than that of electrode system under non-magnetic field. Moreover, Box and Whisker method used in this study gives a lot of information compared other statistical methods.

An indicator of a defect in a high-voltage insulating structure

To monitor the insulation of high-voltage equipment, different kinds of devices, including in situ ones, are used. This paper considers the possibility of using optical indicators—light emitters mounted on the insulation structure of high-voltage lines and substations—as such devices. The principle of operation of an optical indicator is as follows. The electric field distribution over an insulation structure changes with breakage of the integrity of its separate parts; when the potential difference at a damaged section decreases, the voltage at the undamaged part correspondingly increases. A faulty condition of the insulating structure can be determined using the light intensity of an indicator installed in the section of the insulating structure or pylon, since the luminance depends on the voltage drop across its terminals. Experiments showed that such insulation failure can visually be determined without using any additional devices, for example, during routine inspections. It is shown that it is possible to produce indicators that are easy to manufacture and do not require any additional maintenance.