Insulation Oil Research Articles

Submicrosecond electron accelerator based on pulsed transformer

The article describes the test results of a submicrosecond electron accelerator based on a high-voltage pulse transformer. The transformer uses a self-supporting coil design with transformer oil insulation, which ensures high reliability of the device. A transformer-based high-voltage generator produces voltage pulses with an amplitude up to 475 kV, a pulse duration of 0.25 μs (FWHM) with a repetition rate up to 5 pps. A vacuum electron diode with a carbon fiber cathode is installed directly at the generator output and provides electron beam current amplitude up to 1.5 kA in the accelerating gap. An exit window with a titanium membrane 60μm thick is used to output the electron beam into the atmosphere. The exit window can be replaced by a converter to generate pulsed bremsstrahlung X-rays. The accelerator is designed to carry out research in the fields of studying the properties of materials in extreme conditions and the practical application of a pulsed electron beam.

A Study of Inspection for Electrical Safety Systems Case Study Four Locations in Thailand

This research presents study of inspection for electrical safety in electrical system. The four locations are observed. The objective of this research are to study the problems which may be occurred in electrical system and introduce the prevent ways. The four locations consist of 2 factories of paper and 2 animal food factories. For factory of paper, the total electrical load is 18,450 kVA which consists of 10 transformers and another 13,450 kVA which consists of 10 transformers. For the animal food 800 kVA, another is 1000 kVA which each location is a transformer. The inspected systems include transformer, main distribution board, ground and electrical wire systems. The check instruments are test oil maker, thermo scan, earth clamp tester, earth ground tester, infrared tester and outlet tester. The all data from test is analysed to compare among of four locations. For experimental results, it is of found that for transformer, the oil insulation transformer is lower than standard and silica gel is deteriorated and broken box, rubber shield and rubber gasket is broken and damage. For main distribution board, the ground value is lower than standard and the temperature of junction for breaker is high and more dust. For ground system, the ground value is lower than standard and broken. For wire system, the electrical is damaged because of heat and animal.

Compatibility of Printed Photopolymers With Nine-Month Immersion in Common High Voltage Insulation Oils

To enable the use of additively manufactured polymer materials as structural and insulating components within high-voltage pulsed power systems, a better understanding of material compatibility with common pulser material environments is required. This work examines the effect of long-duration contact of printed polymeric components with three high-voltage insulating oils (Shell Diala S2 ZX-A, Luminol TRi, and Royco 602) at room temperature (~25 °C). Test pieces printed using stereolithography (SLA) were evaluated for changes in dielectric strength, mechanical properties, and composition after submersion in insulating oil for a nine-month duration. Gas chromatography–mass spectrometry (GC–MS) was used for compositional analysis on neat and polymer-exposed oils to identify compositional changes that occurred in the oil over the course of the exposure period.

A Fault Diagnosis System of Power Transformers Using Acoustic Characteristics and Neural Network

As one of the most important facilities in the power system, power transformers undertake the crucial tasks of voltage transformation, power distribution and transmission. In the process of operation, the power transformers may have discharges, overheating, insulation degradation, winding and core loosing, solid pollution of insulation oil and some other faults. In order to address the aforementioned issues, a novel fault diagnosis system for power transformer is proposed. Through using the acoustic characteristics of the power transformer and establishing the model of the neural network, the proposed system is demonstrated with high accuracy in the experiment.

Identifying hot spots in GSU power transformers using multiple methods

A routine using multiple methods is proposed for detecting and locating hot spots in power transformers based on thermographic measurements and advanced computational and analytical techniques. The proposed method identifies oxide and hydrocarbon gases dissolved in the insulation oil of power transformers and use the well-established key gas method to provide information about the cause of the hot spots, such as partial discharge, electric arc, and overload heating. The method then uses infrared mappings and temperature measurements to find the approximate location of the hot spots and, finally, the finite element method and an analytical formulation are employed to refine the location of the hotspots and the estimation of their temperature. The proposed method was developed during the design and manufacturing of a commercial 120 MVA generator step-up transformer, produced by a well-renowned manufacturer. The authors conclude that a method is a resourceful tool for identifying hot spots and could be used by manufacturers to identify and predict design and manufacturing failures.

Influence of Aging Derivatives on Properties of Natural Ester Oil

Transformers are the critical component in the power system, which is used for transmission and distribution purposes. Traditionally mineral oil has been used as the liquid insulation medium in the transformer. Owing to poor bio - degradability and availability, it has been widely studied to replace mineral oil with natural ester oil. During the service period of the transformer, oil insulation and paper insulation gets degraded due to aging. This aging results in the formation of furanic compounds in the oil insulation, which will affect the performance of oil insulation and thus the transformer life. In this proposed work, an effort is made to analyze the critical parameters before and after the inclusion of an aging derivative of 2–furfuraldehyde (2-FAL). 2-FAL has been added in the proportion of 20 ppm to investigate the oil’s properties such as breakdown voltage, viscosity, flash point, fire point, and peak absorbance of the UV spectrum. It is observed that there is a lesser impact on the properties with the addition of 20ppm of 2-FAL. Hence it is suggested that the various concentration of 2-FAL may be added to check the quality of oil for further applications.

Experimental study on electric-field-induced droplet generation and breakup in an immiscible medium

Electrical manipulation technique to produce qualified size of droplets has received substantial attention due to its wide applications in biology, medicine and chemistry, where the droplet behaviors could be controlled by adjusting external parameters. Characterization of charged droplet generation and breakup processes is crucial for understanding the basic mechanism of droplet manipulation. In this paper, the formation and breakup processes for charged droplets in dielectric immiscible oil were investigated experimentally at micro-scale by utilizing high-speed photography. The droplet behaviors at the ambient of needle orifice were visualized and captured at various electric field strengths and flow rates while its generation and motion characteristics were analyzed. Novel formation process of micro-droplets emitted from arrayed jets was found and depicted in detail when violent liquid breakup occurred at high voltage. Furthermore, the relationships of electric field and flow rate with characteristics of charged droplet behavior were quantitatively discussed. By consideration of electric field and flow rate, a scaling law to predict droplet size distributions was derived. Besides, a dimensionless model to predict charged droplet positions was given, which showed a linear increasing trend with electric field and time. Graphic abstract

Research on On-line Monitoring and Regulation Technology of Pressure of High Voltage Transformer

In order to analyze the operating status of voltage and current transformers at high voltage levels, the methods of detecting transformer insulation level and infrared temperature are usually used, but such methods usually use manual measurement by portable instruments, and the internal defects of the transformer are difficult to find in time. This article proposes a suitable on-line monitoring method and regulation technology for the insulation oil pressure of high voltage transformers. The defects of the transformer can be judged by the change of the internal oil pressure, which can effectively find faults such as internal short-circuit, degradation, and partial discharge of the transformer. A mechanism is designed to adjust and release the pressure of expanders. The high voltage transformer pressure line monitoring device has developed based on the Internet of Things communication and solar power supply mode, which can monitor the internal operating status of the transformer in real time. When the internal pressure of the transformer suddenly increases, the designed pressure release structure of the expander will automatically rupture, release the internal pressure of the transformer, ensure the safety of the transformer body, and reduce the impact of the accident.

Relationship between the Electrical Characteristics of Molecules and Fast Streamers in Ester Insulation Oil.

The effects of C=C, ester and β-H groups on the ionization potential (IP) and electron affinity (EA) of molecules in natural ester insulation oil were investigated by density functional theory (DFT). The major contribution to the highest occupied molecular orbital (HOMO) comes from the carbon atoms adjacent to C=C. Thus, the IPs of triglycerides decrease as the number of C=C double bonds increases. The C=C in alkanes may also lower the IP. However, the β-H in triglycerides has little effect on the IP, and C=C and β-H have only a small effect on the EAs of the triglycerides because of the major contributions of atoms near the ester group in triglycerides to the lowest unoccupied molecular orbital (LUMO). This study calculated the IPs of 53 kinds of molecules in FR3, which are significantly lower compared with those of molecules in mineral oil (MO) and trimethylolpropane triester without C=C. However, the lightning impulse breakdown voltage (LI Vb) of trimethylolpropane triester is still significantly lower than that of MO at the large gap. Therefore, the transition from slow to fast streamers under low lighting impulse voltage is determined by the ester group rather than by C=C and β-H. The ester group may attract more electrons, impacting itself more compared to alkane in MO and facilitating the transition from slow to fast streamers.

Improvement of RVM Test Interpretation Using a Debye Equivalent Circuit

The aim of this document is to present how the interpretation of the RVM (Recovery Voltage Measurement) test can be improved through the use of a Debye equivalent circuit. As it is described in the literature, the interpretation of the RVM test requires expertise and if the transformer presents a high interfacial polarization it is not possible to diagnose it in detail. The Debye model is proposed in this work for enhancing RVM interpretation. This model is based on an electrical circuit that includes basic R-C components, that allows two interesting features: on one hand, insulation physical effects can be separately represented and, on the other, the values of the R-C components can be calculated from the RVM response. A method is proposed in which using a sweep with a constant number of predefined time constants branches allows us to determine the areas of influence of the different compounds present in the dielectric. Finally, several case studies are presented, in which it is correlated a dielectric oil treatment carried out and the equivalent circuit changes using a sweep allows us to analyze different branches’ sensitivity and to identify the areas of influence of each compound.

Electric Field Simulation Analysis and Insulation Structure Optimization of Transformer Elevating Seat

During long-term operation, impurities and moisture in insulation oil would be absorbed by supporting parts in the elevating seat, which would reduce its insulation strength and leaded to partial discharge. In order to analyse the changing effect of the introduction of supporting parts on long oil gap E-field and optimize the insulation structure, based on the 500kV transformer, FEM was used to calculate the distribution of electric field in elevating seat, the equalizing ball shape was designed and optimized, the influence of elevating seat diameter on the lead surface maximum E-field was analysed. The results showed that after structural optimization, the maximum E-field on lead surface near supporting parts decreased from 8.95kV/mm to 7.82kV/mm, and on the equalizing ball surface decreased from 6.20kV/mm to 5.34kV/mm, with a decrease of 12.63% and 13.87% respectively, which improved the safety and reliability of transformer operation.

Investigating a New Approach for Moisture Assessment of Transformer Insulation System

With the wide application of vegetable insulating oil in power transformers, it is essential to investigate the influence of moisture on the frequency domain dielectric spectrum (FDS) analysis in order to propose an accurate moisture assessment method for vegetable oil-paper insulation system. In this regard, various vegetable oil-paper samples are prepared in a laboratory environment. FDS curves for all samples are obtained at different moisture contents and operating temperatures. A new method to estimate the moisture content in insulation paper is proposed based on the low-frequency characteristic quantity. Also, the effect of operating temperature and water migration between the oil and paper insulation on the FDS analysis is investigated. Based on this analysis, a compensation factor is introduced to eliminate the influence of temperature on paper moisture assessment. Furthermore, an improved normalization method for the temperature effect on the FDS of vegetable oil-paper insulation with different moisture contents is proposed. The proposed moisture assessment and temperature normalization methods are validated thorough their application on an operating power transformer.

Space Charge Transport Characteristic Considering the Non-Uniform Electric Effect of Ion Mobility

Oil-paper insulation is the main insulating medium of converter transformers. Space charge can result in the distortion of electric field in oil-paper insulation, hence it's necessary to analyze the space charge transport characteristic and its influence on the oil-paper insulation. In the paper, the space charge transport characteristic considering the electric field is investigated, and an upstream finite element method is presented to calculate the space charge distribution in oil insulation of converter transformer considering the influence of injection barrier, ion mobility, trapped coefficient and carrier recombination coefficient. Finally, the insulation state of tortuous oil-path is evaluated. Experiments were conducted to analyze the relationship between ion mobility and electric field intensity, the results indicate that the influence of space charge on the electric field intensity in the tortuous oil-path can not be ignored for the design of converter transformer.

Analisis Prediktif Pemeliharaan Minyak Transformator Menggunakan Metode Markov

As one of the main assets that play an important role in the distribution of electricity, the performance of the transformer must be maintained in prime condition. Damage to the transformer insulation oil often causes failure of the transformer. Damage to transformer oil is very difficult to predict, therefore monitoring its condition is very important to do. Dissolved Gas Analysis (DGA) is one og the method to determine the condition of transformer oil, where this method can analyze the condition of the transformer based on the concentration of gas dissolved in oil. A reguler maintenance of transformer oil can prevent the transformer oil from damage or failure of insulation. However, sometimes maintenance is carried out not in a right time that results in a decrease in transformer’s lifetime. In this analysis the value of Total Dissolved Combustible Gas (TDCG) was used to calculate transfomer’s reliability and availability value. Those value then processed using the Markov method to determine the possibilities of proper maintenance time. From the calculation results in this analysis the transformer reliability value in 30 days is 0.886, then the probability of decreasing the reliability value every month is 11.4%. And the value of the availability of the transformer is 0.803 or equal to 293 days. Based on this analysis, in one year the transformer operated properly for 293 days while 72 days the transformer was in an unfavorable condition. So that maintenance should be carried out in 293 days transformer’s condition can be maintained properly.

Power frequency breakdown characteristics of new 3-element mixed insulation oil and oil-impregnated pressboard

Mixed insulation oil has attracted widespread attention in recent years due to its excellent performance. In our previous works, we proposed a novel 3-element mixed insulation oil with superior physical and electrical properties. To promote the application of the mixed insulation oil to transformers, we studied the AC breakdown characteristics of the 3-element mixed insulation oil and the mixed insulation oil-impregnated pressboards and then performed a comparison to Karamay 25# mineral oil. Oil or oil-impregnated pressboard samples with different moisture contents were obtained by moisture absorption or by controlling the drying time. The breakdown tests were carried out at different temperatures in an oil bath. The results showed that the AC breakdown characteristics of the 3-element mixed insulation oil are better than those of mineral oil and that the mixed insulation oil can maintain breakdown strength over a range of moisture contents. The breakdown mechanism of insulation oil is discussed according to the experiment results. Moreover, the breakdown characteristics of the pressboard impregnated with the 3-element mixed insulation oil are also better than those of the pressboard impregnated with mineral oil. These advantages of mixed oil promote application of the 3-element mixed insulation oil to power transformers.

Influence of cellulose paper on gassing tendency of transformer oil under electrical discharge

The intent of this work is to evaluate the influence of cellulose insulation paper on gassing tendency of transformer oil under electrical discharge conditions. For comprehensive enumeration, insulation oil was thermally stressed at 115°C as per ASTM D 1934 with a controlled thermal aging history. The thermally aged oils were considered for gassing tendency evaluation as per ASTM D 6180 (5 hours, 10 kV AC) in the presence of cellulose. Different cellulose Kraft paper proportions including 0, 10, 20, and 30% of aged oil were introduced in to discharge cell. Different cellulose proportions and aging conditions were considered to understand the impact of cellulose while understanding the decomposition aspects of insulation. Diagnostic measurements with those including dissolved gas analysis, moisture, interfacial tension, turbidity, dissolved decay contents, acidity, and dissipation factor were performed before and after gassing tendency evaluation. It was found that, cellulose paper aids significantly in increasing dissolved gases and moisture in oil during electrical discharge. Importantly, diagnostic measurements have shown the ability of paper to absorb certain decomposition products during the discharge process.

A droplet-generator-on-a-chip actuated by ECF (electro-conjugate fluid) micropumps

The traditional power sources for generating droplets are bulky devices such as syringe pumps, constant pressure systems and so on, resulting in difficult integration with other microfluidic components. To overcome this limitation, we propose and develop a droplet generator with its power sources on a chip (22 × 21 × ~ 1 mm). The compact droplet generator consists of two ECF (electro-conjugate fluid) micropumps, a T-junction channel geometry made of SU-8, a water chamber and three I/O ports. In our methodology, the two ECF micropumps are used to pump the continuous phase fluid (oil) directly and the dispersed phase fluid (water) indirectly on a chip. ECF is a kind of functional and dielectric oil, which can generate a strong and active ECF jet when its corresponding electrodes are applied to high DC voltages. Our ECF micropump is composed of triangular prism and silt electrode pairs (TPSEs) and is able to control flow rates precisely on a chip. In our device, the water in oil droplet is formed by the T-junction geometry. Using MEMS technology, we successfully fabricate the droplet-generator-on-a-chip. Span 80 and dibutyl decanedioate (DBD, Tokyo Chemical Industry Co., Ltd) are used as the surfactant and one type of ECF, respectively. Prior to the characteristic experiments of the T-junction generator, we investigate viscosity, electrical conductivity and relative permittivity of the mixtures of DBD and Span 80 at different concentrations (0 wt%, 1 wt%, 3 wt% and 5 wt%). We also research the impact of the mixtures on the performance of ECF micropumps and the wettability of SU-8 fluidic channels. After that, we confirm the flow pattern diagrams of two-phase fluids, the generated droplet diameter and the droplet production rate for our droplet-generator. Therefore, our droplet generator powered by ECF micropumps can realize the droplet generation on a chip.

Modify the Performance of Electrical Transformer by Analysis Oil Aged and Paper Insulation with Nanoparticales

A gradual change in the state and properties of the oil transformer due to aging, which generally leads to break down. Aging of the mineral oil cause permanent harmful change of the ability insulation system. Aging of the mineral oil and water content of paper insulation are simulated at the laboratory by putting the samples of the oil and pieces of insulation paper in a rig (transformer manufactured) and exposed to different temperatures (20Co, 40Co, 60Co, 80Co) for specific durations of time to analysis and improve the performance of the transformer. In this research, the electrical and physical characteristics for the mineral oil and paper insulation have been studied and then repeated by the addition of different concentration of Nanoparticales (ZnO) (0.01, 0.03, 0.05, 0.07)gm/ml then compared with the electrical properties of the pure mineral oil and paper insulation without (ZnO) nanoparticales

Fabrication of Fe3O4@SiO2 Nanofluids with High Breakdown Voltage and Low Dielectric Loss

Insulating oil modified by nanoparticle (often called nanofluids) has recently drawn considerable attention, especially concerning the improvement of electrical breakdown and thermal conductivity of the nanofluids. However, traditional insulating nanofluid often tends to high dielectric loss, which accelerates the ageing of nanofluids and limits its application in electrical equipment. In this paper, three core-shell Fe3O4@SiO2 nanoparticles with different SiO2 shell thickness were prepared and subsequently dispersed into insulating oil to achieve nanofluids. The dispersion stability, breakdown voltages and dielectric properties of these nanofluids were comparatively investigated. Experimental results show the alternating current (AC) and positive lightning breakdown voltage of nanofluids increased by 30.5% and 61%, respectively. Moreover, the SiO2 shell thickness of Fe3O4@SiO2 nanoparticle had significant effects on the dielectric loss of nanofluids.

Optimization of the numerical model of the triggerable LTD spark gap switch

In LTD generators, one of the main parts of the primary discharge circuit is the triggerable spark gap switch. For the cavities with oil insulation, the OrCAD switch model was developed [1–3] by taken into account the effect of the trigger pulse on the triggering time of these switches and its spread. According to the real design, the switch in this model is simulated as a block consisting of six independent spark gaps connected in series. However, because of such detailed description of the switch structure this initial model is quite complex causing significant complications in simulation of the full generator in case it includes numerous switches. To avoid that complexity, in the given paper we investigate the possibility to optimize the initial complex model, and present at the output much less complicated switch model with acceptable simulation error.