Low Energy Degradation Triangle for power transformer health assessment

Dissolved gas analysis (DGA) remains one of the best non-intrusive methods of assessing transformer health and internal faults. However, few approaches identify consistently the incipient faults initiated by low energy degradation processes. The Low Energy Degradation Triangle (LEDT) method formulates three low energy dissolved gases hydrogen (H2), methane (CH4) and carbon monoxide (CO) into a triangular representation to identify early state changes from normal to unhealthy. The approach has been applied to records of DGA from over 200 generator step-up transformers, to large transmission transformers and industrial units. A degradation parameter derived from the LEDT gave early prediction of the failure of more than 90% of transformers that failed or were removed from service. The approach appears to have benefits for transformer health assessment. It also illustrates an association in some transformers between degradation and geomagnetic disturbances. Additionally, the LEDT indicates there is little benefit from oil treatment after low energy degradation has commenced.