Power Oil Transformers - Gas Generation Defects

The article analyzes scientific research in the field of power transformer gas generation defects detecting by methods of Gas Dissolved Analysis (DGA) of transformer oil (chromatographic analysis) and measurement of short-circuit impedance differences. Power transformer defects that cause gas generation and are identified by the results of DGA should be divided conditionally into several groups: defects with circulating currents in windings and short-circuited contours, induced by scattering flux created by wind-ups, defects with an increase in the transient resistances of the grounding nodes of the structural elements, defects with partial discharges of oil gaps and on the surface of solid insulation, defects with a violation of the contact connections of the conductive circuits, defects with overheating and aging of solid insulation and transformer oil. The difference in short-circuit impedance, measured from the sides of the higher and lower voltages, brought to one side of the transformer, is directly dependent on the magnitude of the circulating currents created by the scattering fields, expressed as a percentage, that is, the percentage of the number of uncompensated turns of the windings with current.