Diagnostic degradation process of power transformer insulation system: Harmonic current impact to capability of transformer #7 Pulogadung s/s

Harmonics is a phenomenon that occurs at power systems caused by a non linear load. It would generate high frequency waves resulting from the multiplication of its fundamental waves. Transformer losses can be divided into losses with loads (load losses) and zero load losses (no load losses). Losses that are caused by harmonic current will cause an increase of copper losses and stray flux losses. Whereas harmonic voltage will cause an increase of losses on the transformer´s core. In combination, the existence of harmonic in the transformer´s load will cause the temperature at the top oil increase; hence it will also increase the hot spot temperature. It also cause the technical age of the transformer become shorter due to degradation of the insulation performance. In this paper, the harmonic load´s influence on decreasing capacities and increasing temperature of the transformer will be discussed. Transformer number #7 on Pulogadung substation connected with industrial and household load will be used as example, and several plausible risks will also be discussed.