Power transformer main insulation design improvement using BEM and FEM

Abstract

Insulation system is one of the most important parts of power transformer. Theoretical background for insulation design is given, which includes explanation of dielectric properties of main insulation materials, their withstand to breakdown voltage, their verification by dielectric tests, and statistical data based theory for breakdown probability. Two known numerical methods (BEM and FEM) for calculation of electric field are used and for each numerical method an appropriate model of transformer is made. Safety factors for main insulation between HV and LV winding are calculated after which the oil gap width is reduced. Additional analysis of safety factors and field nonuniformity along windings is performed.Index Terms-numerical calculation, boundary element method, finite element method, electric field, power transformer

A numerical study on effect of intra and inter spaced winding configuration on performance of oil forced transformer cooling system

“…The volume of one turn of the primary winding is 7.068 × 10 À3 m 3 . The total volume of primary winding for 83 number of turns is 0.021,204 m 3 . The volume of one turn of the secondary winding is 6.498 × 10 À3 m 3 .…”

FEM Application for Evaluating and Improving the Insulation System of the 33kV Wound-Core Type Distribution Transformer

“…For each type of test, amount of voltage and time of test are regulated by the standard. For instance, separate source AC duration is one minute, and induced tests may last from twenty minutes to one hour (Mladen M., et al, 2013).…”

“…The insulation system is one of the important parts of a transformer, since its malfunctioning leads to transformer failure. The good insulation structure of a distribution transformer determines that a transformer normally operating during transformers lifetime (Mladen M., et al, 2013). In spite of the improvements done on the insulation materials used in transformer had enabled higher withstand voltages, engineers try to find new design rules to catch up with ever demanding task for increasing the profit and reduce the cost.…”

“…In spite of the improvements done on the insulation materials used in transformer had enabled higher withstand voltages, engineers try to find new design rules to catch up with ever demanding task for increasing the profit and reduce the cost. With the use of modern computers, numerical calculations have become one of the prime tools for solving complicated engineering problems with the goal for improvement in component design and better quality of the final product (Mladen M., et al, 2013). The critical parameter in the breakdown of an insulator is the electric stress, because the minimum thickness required between conductors, and the conductors and the ground, the insulation level is depending on the value of the maximum electric stress (Aydemir A., Özcan K., 2005).…”

Evaluation and improvement of the main insulation structure of 33kV distribution transformer based on FEM

“…Most of the power transformers in current use are oil-immersed power transformers [4]. Many studies tended to improve the insulation materials used in the high voltage devices in order to withstand higher voltages, yet studies and researches are progressing in order to find new insulation designs, in order to satisfy the increasing demand for the electrical energy, maximize the profit with minimum cost [5], [6]. A transformers are exposed to certain conditions during its normal operation while being in service, such as impulse overvoltages, or lighting impulse during sever weather conditions, therefor, certain tests that simulate these conditions which a transformer must be subjected to them in order to fulfill that a transformer can withstand such conditions.…”