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Reliability Analysis and Overload Capability Assessment of Oil-Immersed Power Transformers

School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000, China
School of Mathematics and Computer Science, Northwest University for Nationalities, Lanzhou 730030, China
School of Statistics, Dongbei University of Finance and Economics, Dalian 116025, China
Center for Energy and Environmental Policy Research, Beijing Institute of Technology, Beijing 100081, China
School of Management and Economics, Beijing Institute of Technology, Beijing 100081, China
Author to whom correspondence should be addressed.
Academic Editor: Issouf Fofana
Energies 2016, 9(1), 43;
Received: 4 November 2015 / Revised: 23 December 2015 / Accepted: 5 January 2016 / Published: 14 January 2016
(This article belongs to the Special Issue Power Transformer Diagnostics, Monitoring and Design Features)
PDF [1957 KB, uploaded 14 January 2016]


Smart grids have been constructed so as to guarantee the security and stability of the power grid in recent years. Power transformers are a most vital component in the complicated smart grid network. Any transformer failure can cause damage of the whole power system, within which the failures caused by overloading cannot be ignored. This research gives a new insight into overload capability assessment of transformers. The hot-spot temperature of the winding is the most critical factor in measuring the overload capacity of power transformers. Thus, the hot-spot temperature is calculated to obtain the duration running time of the power transformers under overloading conditions. Then the overloading probability is fitted with the mature and widely accepted Weibull probability density function. To guarantee the accuracy of this fitting, a new objective function is proposed to obtain the desired parameters in the Weibull distributions. In addition, ten different mutation scenarios are adopted in the differential evolutionary algorithm to optimize the parameter in the Weibull distribution. The final comprehensive overload capability of the power transformer is assessed by the duration running time as well as the overloading probability. Compared with the previous studies that take no account of the overloading probability, the assessment results obtained in this research are much more reliable. View Full-Text
Keywords: current measurement; losses; power transformers; reliability estimation; transformer windings current measurement; losses; power transformers; reliability estimation; transformer windings

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Wang, C.; Wu, J.; Wang, J.; Zhao, W. Reliability Analysis and Overload Capability Assessment of Oil-Immersed Power Transformers. Energies 2016, 9, 43.

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