S. Chandrasekar

Bio: S. Chandrasekar is an academic researcher. The author has contributed to research in topics: Partial discharge & Mineral oil. The author has an hindex of 3, co-authored 9 publications receiving 22 citations.

EFFECT OF NANO-SiO2 PARTICLES ON PARTIAL DISCHARGE SIGNAL CHARACTERISTICS OF FR3 TRANSFORMER OIL

Abstract: Liquid insulation for high voltage transformer applications based on natural esters derived from abundantly available vegetable oils are becoming popular in recent times. Since these natural ester based oils have environmental advantages and superior thermal performance, electrical utilities are slowly replacing the conventional mineral oils with natural ester based vegetable oils. FR3 oil, which is a soya based natural ester oil with superior dielectric and thermal characteristics, is becoming popular as an alternate insulating medium for high voltage transformers. With recent developments in nanotechnology field, it is possible to enhance the dielectric performance characteristics of natural ester based oils, which is a major constraint for high voltage transformer applications. However few research reports are only available in the area of nanofluids based on natural esters for high voltage insulation applications. In depth analysis and collection of large data base of insulation performance of natural ester based vegetable oils is important to improve the confidence level over nano-fluids based on natural esters. Considering these facts, in the present work, partial discharge characteristics of  nano-SiO2 modified FR3 oil at different electrode configurations are investigated at different %wt filler concentrations. Important parameters such as partial discharge inception voltage, stable PD formation voltage, partial discharge amplitude at different voltage magnitude and PD signal frequency characteristics are evaluated. From the results, it is observed that the partial discharge performance of FR3 oil is significantly improved with the addition of nano-SiO2 filler. Since in recent times FR3 oil is commercially used in many transformers, these results will be useful for enhancing the dielectric strength of high voltage transformers.

Investigations on Dielectric Performance Characteristics of Natural Ester based Nano-Fluids for Power Transformer Applications

Abstract: Liquid insulation for high voltage transformer applications based on natural esters derived from abundantly available vegetable oils are becoming popular in recent times. Since these natural ester based oils have environmental advantages and superior thermal performance, electrical utilities are slowly replacing the conventional mineral oils with natural ester based vegetable oils. FR3 oil, which is a soya based natural ester oil with superior dielectric and thermal characteristics, is becoming popular as an alternate insulating medium for high voltage transformers. With recent developments in nanotechnology field, it is possible to enhance the dielectric performance characteristics of natural ester based oils, which is a major constraint for high voltage transformer applications. However few research reports are only available in the area of nanofluids based on natural esters for high voltage insulation applications. In depth analysis and collection of large data base of insulation performance of natural ester based vegetable oils is important to improve the confidence level over nano-fluids based on natural esters. Considering these facts, in the present work, dielectric properties such as breakdown strength, capacitance, tan delta, relative permittivity and volume resistivity of nano-SiO2 modified FR3 oil are investigated at different %wt filler concentrations. From the results, it is observed that the dielectric performance of FR3 oil is significantly improved with the addition of nano-SiO2 filler. Since in recent times FR3 oil is commercially used in many transformers, these results will be useful for enhancing the dielectric strength of high voltage transformers.

UNDERSTANDING THE LIGHTNING DISCHARGE WITHSTAND AND BREAKDOWN CHARACTERISTICS OF NANO SiO2 MODIFIED MINERAL OIL FOR TRANSFORMER APPLICATIONS

Abstract: The successful operation of electrical power system network depends on the performance of insulation provided in the high voltage power transformers. Recent output of many research works confirm that the nano modified insulation system provides enhanced dielectric and thermal characteristics when compared with conventional system. Now a days nano modified mineral oils are considered as an alternative to conventional mineral oils as a dielectric insulation fluid in power transformers, leading to the improved dielectric strength of apparatus with further reduction in the size and manufacturing cost. Since distribution transformers are mainly used in outdoor applications, understanding its lightning discharge withstand and breakdown characteristics of nano modified insulating fluid is a vital issue. In this paper laboratory experimental works are performed to understand the lightning discharge performance of mineral oil along with SiO2 nanofiller at different %wt concentration such as 0.01%, 0.05% and 0.1%. Standard lightning impulse voltage of 1.2/50 µs time period with both positive and negative polarity is used in the experiments. Results illustrate that the nano modified mineral oil significantly improves the lightning impulse withstand and breakdown strength of insulation system.Â

Analysis of Partial Discharge Signal Characteristics of Nano-Mineral Oil for Transformer Condition Monitoring Applications

Abstract: Transformer is an expensive and key component in an electric power transmission network. Most of the failure of transformer occurs due to degradation of insulation oil, which further leads to major economical losses and power shutdown. Advancements in nanotechnology has given horizons for the development of nanofluids for transformer insulation applications. Understanding the enhancements in dielectric properties of nanofiller added mineral oil is a hot research area. In recent times, partial discharge (PD) detection and analysis is a well recognized insulation condition monitoring technique for transformers. However, reports on PD signal characteristics of nano filler added mineral oil is scanty. This paper attempts to investigate the PD characteristics of SiO2 nanofiller added mineral oil at different %wt concentrations of nanofiller material. Major PD source normally experienced in transformers i.e. corona discharge due to non-uniform electric field was simulated in the laboratory using needle-plane electrode configuration and the corresponding PD signals were measured using wide band PD detection system. Important PD characteristics such as inception voltage, stable PD formation voltage, PD amplitude with respect to increase in voltage stress and PD signal frequency spectrum were evaluated. Results clearly show that addition of SiO2 nanofiller material in the base mineral oil enhances PD performance of mineral oil and these results will be useful for electrical utilities for developing effective condition monitoring system for transformers.

Investigations on Dielectric Properties of Nano SiO2-Mineral Oil for Transformer Insulation Applications

Abstract: Successful operation of electric power transmission and distribution network depends on the consistency of power transformers. Any unscheduled outage due to a faulty transformer leads to expensive and time consuming repair work and affects the entire power system reliability. Majority of the power transformer faults occur due to aging and degradation of oil insulation. Mineral oil is being used as a liquid dielectric in transformers for a longer period of time. In general, periodic monitoring of electrical, physical and chemical properties will certainly give information about the aging and deterioration of insulating oil. In recent times, advancements in nanotechnology has given scope for the development of nano-dielectrics for transformer insulation applications. Many research works are being carried out to understand the dielectric performance enhancements in nano-modified insulating oils for high voltage applications. In the present work, dielectric properties of nano-SiO2 modified mineral oil is investigated. Detailed reports on the characteristics of nano SiO2-modified mineral oil such as breakdown strength, loss factor, volume resistivity, viscosity, flash point and fire point are scanty. Hence, this paper attempts to investigate the above mentioned characteristics of SiO2 nanofiller added mineral oil at different %wt concentrations of nanofiller material. Results clearly show that addition of SiO2 nanofiller material in the base mineral oil enhances dielectric performance of mineral oil. These results will be useful for electrical utilities in improving the design aspects, identifying the root cause of insulation failures and carrying out the preventive maintenance activities of transformers.

Nanofluids in the Service of High Voltage Transformers: Breakdown Properties of Transformer Oils with Nanoparticles, a Review

Abstract: The continuous development of electrical systems and high voltage transformers builds the need for looking for new insulating media or to improve the insulating properties of commercially available transformer oils (TO) by various modification techniques. One of these techniques is the modification of existing mineral oils by the addition of different types of nanoparticles in various concentrations. These types of materials, suspensions of nanoparticles called nanofluids, have found numerous applications in the energy industry, especially in heat exchanger systems and solar cells. Much research has been done on attempts to replace mineral oils (MO), which are harmful for the environment, with natural ester oils (NE), but to make this possible, it is necessary to improve the insulating properties of these oils, for example by adding nanoparticles. This paper presents an extensive overview of the insulating properties; including for AC, DC and the lightning impulse breakdown voltage; for both mineral and natural ester oils containing various type of nanoparticles (NP). It is presented that the use of nanofluids could improve the efficiency of existing high voltage infrastructures with a low financial cost.

Impact of Fe3O4, CuO and Al2O3 on the AC Breakdown Voltage of Palm Oil and Coconut Oil in the Presence of CTAB

Abstract: This paper presents an experimental study on the AC breakdown voltages of Refined, Bleached and Deodorized Palm Oil (RBDPO) Olein and Coconut Oil (CO) in the presence of conductive (Iron (II,III) Oxide, Fe3O4), semi-conductive (Copper (II) Oxide, CuO) and insulative (Aluminium Oxide, Al2O3) nanoparticles without and with surfactant. The type of surfactant used in this study was Cetyl Trimethyl Ammonium Bromide (CTAB). The volume concentrations range of Fe3O4, CuO and Al2O3 was varied from 0.001% to 0.05%. Transmission Electron Microscope (TEM) was used to characterize the nanoparticles in RBDPO and CO. AC breakdown voltage tests were carried out for RBDPO and CO of which the AC breakdown voltage at 1% probability was determined based on Weibull distribution. It is found that only Al2O3 can improve the average AC breakdown voltage of RBDPO and CO. The AC breakdown voltages at 1% probability for RBDPO and CO can be improved through introduction of Fe3O4, CuO and Al2O3 at certain volume concentrations. Al2O3 provides the highest enhancement of AC breakdown voltages at 1% probability for RBDPO and CO with the highest percentage of improvement can be up to 52%. CTAB has no clear effect on the improvement of AC breakdown voltages of RBDPO and CO based Fe3O4, CuO and Al2O3 nanofluids.

Statistical Investigation of Lightning Impulse Breakdown Voltage of Natural and Synthetic Ester Oils-Based Fe 3 O 4 , Al 2 O 3 and SiO 2 Nanofluids

Abstract: The characteristics of lighting impulse breakdown voltage (LI-BDV) constitute key performance indicators of insulating materials, especially in insulations based on liquids and liquid-paper for high voltage applications Encouraged by environmental policies worldwide, new insulating liquids have been developed in recent years Among these are natural and synthetic esters that are currently considered as potential substitutes for traditional mineral oils due to their environmentally friendly properties Recent technological advances have shown that the addition of specific nanoparticles (NPs) to insulating liquids can improve both the dielectric withstand voltage and the thermal behavior of liquid insulations This paper examines the effects of some NPs on the negative LI-BDV of natural and synthetic ester liquids, namely MIDEL 1204 and MIDEL 7131, respectively The used NPs are Fe3O4, Al2O3 and SiO2 The LI-BDV measurements are executed in accordance with IEC 60060 standard, and the breakdown voltage with 1% probability risk (ie, the lowest possible breakdown voltage) was also estimated The experimental results showed that these NPs improved the LI-BDV of both synthetic and natural ester liquids and an optimal concentration of NPs can be determined Statistical analysis was also performed to check the compliance of the experimental results with the most common probability distributions, normal and Weibull distributions

Influence Analysis and Prediction of ESDD and NSDD Based on Random Forests

Abstract: Equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) measurements are a basic requirement of power systems. In order to predict the site pollution severity (SPS) of insulators, a new method based on random forests (RFs) is proposed. Using mutual information (MI) theory and RFs, the weights of factors related to the SPS of insulators are analyzed. The samples of contaminated insulators are extracted from the transmission lines of high voltage alternating current (HVAC) and high voltage direct current transmission (HVDC). The regression models of RFs and support vector machines (SVM) are constructed and compared, which helps to support the lack of information in predicting NSDD in previous works. The results are as follows: according to the mean decrease accuracy (MDA), mean decrease Gini, (MDG), and MI, the types of the insulators (including surface area, surface orientation, and total length) as well as the hydrophobicity are the main factors affecting both ESDD and NSDD. Compared with NSDD, the electrical parameters have a significant effect on ESDD. For the influence factors of ESDD, the weights of the insulator type, hydrophobicity, and meteorological factors are 52.94%, 6.35%, and 21.88%, respectively. For the influence factors of NSDD, the weights of the insulator type, hydrophobicity, and meteorological factors are 55.37%, 11.04%, and 14.26%, respectively. The influence voltage level (vl), voltage type (vt), polarity/phases (pp) exerted on ESDD are 1.5 times, 3 times, and 4.5 times of NSDD, respectively. The influence that distance from the coastline (d), wind velocity (wv), and rainfall (rf) exert on NSDD are 1.5 times, 2 times, and 2.5 times that of ESDD, respectively. Compared with the natural contamination test and the SVM regression model, the RFs regression model can effectively predict the contamination degree of insulators, and the relative error of the predicted ESDD and NSDD is 8.31% and 9.62%, respectively.

Breakdown in Nanofluids: A Short Review on Experimental Results and Related Mechanisms

Abstract: Nanofluids seem to gradualy become an alternative to traditional insulating liquids, such as transformer oil. In this paper, a short review of experimental results as well as of possible breakdown mechanisms and of some of the factors affecting the breakdown strength of the said fluids is conducted. Most of the reports suggest that the addition of nanoparticles in insulating liquids improves the breakdown strength. However, some reports that contradict the above are also to be found. In view of this, an outline of future research is discussed. This review does not encompass all possible effects, parameters and factors affecting nanofluids but it is solely concerned with breakdown strength.