Improved risk analysis through failure mode classification according to occurrence time

Nowadays, risk-based asset management is commonly adopted throughout electricity utilities as a business model. Potential risks are registered, and after selection the influence of the risk is assessed. This paper discusses the possible shortcomings with regard to current risk assessment methods. Based on an improved risk assessment approach, it is shown that risk might be underestimated when the economic loss of failures are not incorporated in the assessment. Furthermore, with the advent of the intelligent networks of the future (intelligent grid), the more user-centric requirements should anticipate an improved risk assessment approach for asset management. Moreover, emerging dynamic pricing, demand-side-management, two-way information transfer, etc., might provide tools to measure the reliability indicator “Energy Not Supplied” even at distribution network levels. In this contribution, a case study of 50/10 kV transformer failures is analysed according to the failure occurrence time and loss of load. The results are applied as input for an improved risk assessment approach, which, ultimately, reveals that risks are likely to be underestimated. In conclusion, we show that without considering the occurrence time of failure, the risks of failures will be underestimated for 7% to 13%.