The paper is based on the experimental investigation of accelerated stresses on insulation of power transformer. The effects of individual thermal and electrical stresses have been graphically presented. The factors a...The paper is based on the experimental investigation of accelerated stresses on insulation of power transformer. The effects of individual thermal and electrical stresses have been graphically presented. The factors accelerated thermal aging factor (ATAF) and accelerated electrical aging factor (AEAF) have been introduced, it helps to understand the contribution of thermal and electrical stresses and degradation trends of insulating properties. The accelerated aging factors have been mathematically correlated with different properties of insulation such as moisture, breakdown voltage (BDV), tan delta and resistivity. These parameters were determined experimentally for fresh oil samples and for samples subjected to accelerated aging.展开更多
Three electrorheological fluids (ERFs) of recently synthesized Polyaniline.HCl and Cellulose fluids as well as a commercial product from Fludicon? (Germany), were evaluated with a two-electrode probe unit and by Diele...Three electrorheological fluids (ERFs) of recently synthesized Polyaniline.HCl and Cellulose fluids as well as a commercial product from Fludicon? (Germany), were evaluated with a two-electrode probe unit and by Dielectric Analysis (DEA). The study was a part of an ongoing medical device development project. The dielectric response times were calculated using the critical peak frequency in a corresponding Debye plot of Tan Delta (loss factor/permittivity) vs. log frequency. The DEA revealed the response times (tau, τ) in ms. The Fludicon? ERF was DEA durable (repeat cycles produced same results) and the τ was temperature dependent: 16 ms at 25°C and 0.16 ms at 80°C. The Cellulose ERF was somewhat DEA durable and the τ was 5.5 ms at 25°C and 0.21 ms at 80°C. The response times were logarithmic with the temperature (°C) with a correlation coefficient of >0.98 for the Cellulose and Fludicon? ERFs. The Polyaniline ERF had a τ of 53 ms at 25°C in the 1st DEA run and there was no indication of a τ for the remaining DEA tests.展开更多
Dynamic mechanical behaviour of resorcinol-formaldehyde matrix and its composites reinforced with natural fibers of Luffa cylindrica (LC) has been studied. The effects of fiber loading, alkali treatment on fiber, temp...Dynamic mechanical behaviour of resorcinol-formaldehyde matrix and its composites reinforced with natural fibers of Luffa cylindrica (LC) has been studied. The effects of fiber loading, alkali treatment on fiber, temperature and frequency on storage modulus and mechanical-loss factor of the composites were studied. The dynamic mechanical behaviour of the composites and pure matrix has been investigated in the frequency range from 0.1 Hz to 10 Hz and temperature range from 26℃ to 100℃. The experimental results show that the values of storage modulus of the composites increase with increase in fiber loading. The storage modulus of treated LC fiber composites were found to be enhanced when compared with the untreated fiber composites. It was also found that mechanical-loss factor was more when untreated LC fibers were incorporated in the composites and decreased with the incorporation of treated LC fiber. The storage modulus of all the composites increased with frequency but decreased with rise of temperature. The glass transition temperature of the composites was evaluated from the peaks of tan delta variations.展开更多
With the prevailing power scenario, every watt-second of electrical energy has its own merit in satisfying the consumer demand. At the state of such a stringent energy demanding era, failure of a power generation equi...With the prevailing power scenario, every watt-second of electrical energy has its own merit in satisfying the consumer demand. At the state of such a stringent energy demanding era, failure of a power generation equipment compounds the energy constraints which will not only result in a huge loss of generation but also have an impact on capital revenue. The unexpected failure of generator step-up （GSU） transformer is espe- cially a major disturbance in the power system operation and leads to unscheduled outages with power delivery problems. The time lag in bringing back the equipment in service after rectification or replacement may increase the criticality as the process involves mobilization of spares and maintenance professionals. Hot atmosphere existing in the vicinity of thermal power stations running round-the- clock with more than 100% plant load factor （PLF） increases the thermal stress of the electrical insulation which leads to premature failure of windings, bushings, core laminations, etc. The healthy state of the GSU transformer has to be ensured to minimize the loss of power generation. As the predication related to failure of a GSU transformer is associated with some uncertainties, a fuzzy approach is employed in this paper along with actual field data and case studies for the well-being analysis of GSU transformer.展开更多
文摘The paper is based on the experimental investigation of accelerated stresses on insulation of power transformer. The effects of individual thermal and electrical stresses have been graphically presented. The factors accelerated thermal aging factor (ATAF) and accelerated electrical aging factor (AEAF) have been introduced, it helps to understand the contribution of thermal and electrical stresses and degradation trends of insulating properties. The accelerated aging factors have been mathematically correlated with different properties of insulation such as moisture, breakdown voltage (BDV), tan delta and resistivity. These parameters were determined experimentally for fresh oil samples and for samples subjected to accelerated aging.
文摘Three electrorheological fluids (ERFs) of recently synthesized Polyaniline.HCl and Cellulose fluids as well as a commercial product from Fludicon? (Germany), were evaluated with a two-electrode probe unit and by Dielectric Analysis (DEA). The study was a part of an ongoing medical device development project. The dielectric response times were calculated using the critical peak frequency in a corresponding Debye plot of Tan Delta (loss factor/permittivity) vs. log frequency. The DEA revealed the response times (tau, τ) in ms. The Fludicon? ERF was DEA durable (repeat cycles produced same results) and the τ was temperature dependent: 16 ms at 25°C and 0.16 ms at 80°C. The Cellulose ERF was somewhat DEA durable and the τ was 5.5 ms at 25°C and 0.21 ms at 80°C. The response times were logarithmic with the temperature (°C) with a correlation coefficient of >0.98 for the Cellulose and Fludicon? ERFs. The Polyaniline ERF had a τ of 53 ms at 25°C in the 1st DEA run and there was no indication of a τ for the remaining DEA tests.
文摘Dynamic mechanical behaviour of resorcinol-formaldehyde matrix and its composites reinforced with natural fibers of Luffa cylindrica (LC) has been studied. The effects of fiber loading, alkali treatment on fiber, temperature and frequency on storage modulus and mechanical-loss factor of the composites were studied. The dynamic mechanical behaviour of the composites and pure matrix has been investigated in the frequency range from 0.1 Hz to 10 Hz and temperature range from 26℃ to 100℃. The experimental results show that the values of storage modulus of the composites increase with increase in fiber loading. The storage modulus of treated LC fiber composites were found to be enhanced when compared with the untreated fiber composites. It was also found that mechanical-loss factor was more when untreated LC fibers were incorporated in the composites and decreased with the incorporation of treated LC fiber. The storage modulus of all the composites increased with frequency but decreased with rise of temperature. The glass transition temperature of the composites was evaluated from the peaks of tan delta variations.
文摘With the prevailing power scenario, every watt-second of electrical energy has its own merit in satisfying the consumer demand. At the state of such a stringent energy demanding era, failure of a power generation equipment compounds the energy constraints which will not only result in a huge loss of generation but also have an impact on capital revenue. The unexpected failure of generator step-up （GSU） transformer is espe- cially a major disturbance in the power system operation and leads to unscheduled outages with power delivery problems. The time lag in bringing back the equipment in service after rectification or replacement may increase the criticality as the process involves mobilization of spares and maintenance professionals. Hot atmosphere existing in the vicinity of thermal power stations running round-the- clock with more than 100% plant load factor （PLF） increases the thermal stress of the electrical insulation which leads to premature failure of windings, bushings, core laminations, etc. The healthy state of the GSU transformer has to be ensured to minimize the loss of power generation. As the predication related to failure of a GSU transformer is associated with some uncertainties, a fuzzy approach is employed in this paper along with actual field data and case studies for the well-being analysis of GSU transformer.
