Manoj Pradhan - Academia.edu (original) (raw)

Papers by Manoj Pradhan

Page 1. Monitoring the SF6 Pressure Level in Metal-Enclosed Switchgear to Detect Gas Leakages Luk... more Page 1. Monitoring the SF6 Pressure Level in Metal-Enclosed Switchgear to Detect Gas Leakages Lukas Graber1* and Manoj Kumar Pradhan2 1 ETH Zurich, Switzerland 2 University of Queensland, Australia *E-mail: lgraber@ieee.org ...

In the present work, a carefully designed experimental set up has been used to measure breakdown ... more In the present work, a carefully designed experimental set up has been used to measure breakdown voltages (BDV) of LN2 under realistic conditions which are likely to be encountered in the complex electrical systems in the field. Different electrode profiles viz. sphere-sphere, needle-plane has been used to simulate various practical conditions. The Authors particularly focuses on the breakdown characteristics of LN2 under composite voltages viz. AC superimposed with positive DC, AC superimposed with negative DC. It is observed that DC bias reduces the AC breakdown voltage considerably.

IEEE Transactions on Power Delivery, 2005

Inadvertent failure of power transformers has serious consequences on the system reliability, eco... more Inadvertent failure of power transformers has serious consequences on the system reliability, economics, and the revenue accrual. An accurate estimation of transformer life can, to a very large extent, mitigate the problems, besides satisfying the conflicting requirements of optimum utilization of the equipment and safeguarding the reliability. In this endeavour, the authors have planned long duration aging experiments on scaled-down

IEEE Transactions on Power Delivery, 2003

The degradation of electrical insulation in transformers is more often due to thermal stress. In ... more The degradation of electrical insulation in transformers is more often due to thermal stress. In this paper, authors have attempted to work out a method of assessing the magnitude of temperature and the hottest region in the body of a large transformer with a reasonable degree of accuracy. A theoretical model has been developed based on boundary value problem of heat conduction in transformer winding using finite integral transform techniques. The model requires, in addition to electrical parameters of the transformer, information on the actual design data. The authors believe that this model predicts HST with precision and also indicates a possibility of online data acquisition.

IEEE Transactions on Power Delivery, 2004

The degradation of electrical insulation in transformers is traced to thermoelectric processes. E... more The degradation of electrical insulation in transformers is traced to thermoelectric processes. Existence of localized hot regions due to thermal insulating properties of electrical insulation would cause thermal runaway around these regions. In an earlier paper [1], the authors presented analytical methods for estimating the temperature and its distribution at different points of the transformer based on a closed-form mathematical technique using a generalized heat conduction (GHC) model. Certain aspects of the inhomogeniety of the several components of the winding and incorporation of distributed heat source were not addressed. Also, a rigorous treatment involving the changes in winding resistance, which was built into the thermal model as an empirical correction factor, has now been modified and incorporated in the GHC. These considerations have now improved the accuracy of estimation of hottest spot temperature.

The degradation of electrical insulation in transformers is more often due to thermal stress. In ... more The degradation of electrical insulation in transformers is more often due to thermal stress. In this paper authors have attempted to work out a means of assessing the magnitude of temperature and the hottest region in the body of a large transformer with a reasonable degree of accuracy. A theoretical model has been developed based on boundary value problem of heat conduction in transformer winding using finite integral transform techniques. The model requires, in addition to electrical parameters of the transformer, information on the actual design data. The authors believe that this model predicts HST with precision and also indicates a possibility of on-line data acquisition.

Absnocr-Inordinate temperature rise in a power IransComer due to load current h known to be the m... more Absnocr-Inordinate temperature rise in a power IransComer due to load current h known to be the most important faclor in causing rapid degradation OC ils insulation and decids thc optimum load catering ability or the loadability at a translnrmer. The Top Oil Temperature (TOT) and

In the recent past, a considerable amount of work has been published on the dynamics of aging of ... more In the recent past, a considerable amount of work has been published on the dynamics of aging of oil impregnated paper (OIP) insulation in transformers. The insulation is always subjected to stresses of different types at the same point in time. Among the more important stress are, electrical, thermal and their combination. Insulating properties of both solid (cellulose paper) and

Power and Station transformers are among the more expensive and critical elements of a power syst... more Power and Station transformers are among the more expensive and critical elements of a power system, so much so, failure of this component entails unacceptably long intermptions. Further, unscheduled, or, inadvertent failure thereof, has serious consequences on the maintenance of system reliability and revenue accrual. In principle, ensuring the reliability power transformers is a two-step process, involving the detection of an impending failure in its formative stage so as to preclude catastrophic failures and if, for any reason, an outage occurs, evolving an appropriate replacement strategy of the failed units in a minimum possible time. In diagnostic testing, physical parameters used as indices of impending failure shall he sensitive to the amount of ageing and shall possesses a reasonably high degree of correlation with dielectric strength and mechanical strength. Concerted research work is being carried out, the world over, to try and identify such properties of insulation as are sensitive to the amount of degradation. The authors of this paper aim to suggest techniques for acquisition and analysis of ageing data in order to propose a conditionmonitoring schedule.

IEEE Transactions on Power Delivery, 2005

IEEE Transactions on Power Delivery, 2003

IEEE Transactions on Power Delivery, 2004

The degradation of electrical insulation in transformers is more often due to thermal stress. In ... more The degradation of electrical insulation in transformers is more often due to thermal stress. In this paper authors have attempted to work out a means of assessing the magnitude of temperature and the hottest region in the body of a large transformer with a reasonable degree of accuracy. A theoretical model has been developed based on boundary value problem of heat conduction in transformer winding using finite integral transform techniques. The model requires, in addition to electrical parameters of the transformer, information on the actual design data. The authors believe that this model predicts HST with precision and also indicates a possibility of on-line data acquisition.