Particle Contamination Levels in Oil-Filled Large Power Transformers

A study of particle levels in transformer oil was conducted, covering about 200 samples taken from field and factory units. Factory samples were included to determine a relative base condition on which to compare field data. Particle distribution curves show size and count relationship in transformers. The particles were studied also by Atomic Absorption Spectroscopy to measure the content of iron, copper and other common metals expected. Particle analysis can supplement more standard laboratory techniques to judge the condition of oil in operating power transformers. The diagnostic value of such analysis, especially in determining pump performance problems, is illustrated with examples.