Abstract

SINGH, A.  and  SWANSON, A.G.. Development of a plant health and risk index for distribution power transformers in South Africa. SAIEE ARJ [online]. 2018, vol.109, n.3, pp.159-170. ISSN 1991-1696.

The health index is a part of the life cycle management tools for key assets. It allows for customization of maintenance plans for transformers depending on their condition. This optimises resources and allows for early detection of faults while allowing sufficient time to plan interventions to address problematic transformers. The index addresses the weighting between long term assessments (paper degradation), and short to medium term assessments (dissolved gas analysis). In addition to the Total Dissolved Combustible Gases method of dissolved gas analysis, methods looking at the ratio of the various gases present in the oil were employed for more accurate dissolved gas analysis interpretation. Oil quality indicators were also used in the index as the life of the paper relies on the quality of the insulating oil, which if allowed to oxidize, sludge and degrade would put the transformer in worse condition, it should also be represented in any health assessment of transformers. A case study was presented and indicated that with the correct weightings of the criteria, the plant health index would correctly predict whether a transformer would fail. For the transformers where the plant health index did not predict failure, a network performance and ancillary equipment score was introduced and combined with the plant health index for a risk index. It was shown that healthy transformers on poorly performing networks could be better categorised. It was also shown that a score for the ancillary equipment could be used to better categorise the transformers. The risk index allows for better inspection, maintenance and replacement of equipment.

Keywords : health index; risk index.

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