METHODS FOR REDUCTION OF STRAY LOSS IN HIGH CURRENT LV REGIONS OF LARGE POWER TRANSFORMERS USING FEM ANALYSIS
Linu Alias
PG Scholar Department of EEE, Anna University Regional office, Madurai – 625007, Tamil Nadu, India
V Malathi
Faculty Department of EEE, Anna University Regional office, Madurai – 625007, Tamil Nadu, India
40-52
Vol: 5, Issue: 3, 2015
Receiving Date:
2015-05-16
Acceptance Date:
2015-06-14
Publication Date:
2015-07-16
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Abstract
In large power transformers, more than 20% of the total load loss is the stray loss in structural
components. The biggest part of stray loss takes place in the transformer tank. As the transformer
ratings increase, the stray loss problem becomes increasingly significant resulting in higher
temperatures and local hot spots that reduce the transformer life. Analytical and numerical methods
have been applied for the evaluation of stray loss. Stray losses in transformer covers depend on the
distribution of leakage flux produced by strong induced fields. Due to the heavy current flow in Low
Voltage (LV) windings, the strong magnetic flux linking the transformer tank causes over heating of
the tank walls which are near the high current bushings of transformer. While considering the LV side
the current may even goes to around 9000A for a generator transformer for the kind we have
considered. This work presents a 3-D Finite Element Analysis of the tank walls to verify the solution
of overheating problem. The overheating results are analyzed and discussed for the case of a
290MVA 235/15.75 KV generator transformer.
Keywords:
stray loss, induced fields, local hot spots, leakage flux, generator transformer,
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