Transformer and System Reliability
National Grid Electricity System Operator
National Grid TO Innovation Team
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Innovation Funding Incentive
Gas Distribution Networks
At present the risk and criticality approach to transformer maintenance and
replacement is based on a relatively crude 3 point scale of criticality and a
matrix. This method may be capable of improvement if a real network model is
used together with an understanding of possible interactions between failures.
Generally a transformer outage is of little consequence, but two or more
simultaneous outages on certain parts of the network could have severe
consequences. Identifying these situations and the sensitivity to linked failures is
important for the correct and timely replacement of the most critical units. As far
as can be determined there is nothing significant published on the interaction of
transformer reliability and overall system reliability. One of the final parts of the
transformer lifetime project which is in progress was to look at this area but it is
unlikely that there will be time on this project to start this work.
This project will deliver a methodology for assessing the maintenance and
replacement strategies for transformers against system reliability requirements.
In particular the derivation of transformer replacement priority from asset health
index and perceived system criticality can be greatly refined using a detailed
knowledge of transformer failure modes (common mode, sympathetic and
hidden failures). The availability of such a methodology will ensure an optimum
and justifiable prioritisation of transformer replacement and maintenance.