Dinorwig Thermal Cycling and Cable Rating
National Grid Electricity System Operator
National Grid TO Innovation Team
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Innovation Funding Incentive
Gas Distribution Networks
Over recent years the 400kV electricity connection for Dinorwig
Power Station has suffered from poor reliability problems
associated with abnormally high Dissolved Gas levels in the
cable fluid. These levels have forced National Grid Electricity
Transmission to switch out the Dinorwig-Pentir 1 circuit in 2012
resulting in a circuit outage to replace the ‘gassing’ stop joint
accruing costs of circa £150k per day.
An identical issue occurred in 2011 on the Dinorwig-Pentir 2
circuit with identification of another ‘gassing’ stop joint.
These incidents have prompted an action to probe further into
the likely root cause as well as further studies to understand
the resultant effects (pertaining to stop joints) from an aspect of
The project aims to undertake a detailed study on the thermal
cycling effects on the Dinorwig cable circuits with particular
emphasis to the stop joints. The live data captured on site will
enable a model to be developed of the stop joint using Finite
Element Analysis. The results of this analysis should yield
better understanding on the expected performance of these
stop joints under differing load patterns as well as shed light on
any relevant amendments regarding assumptions made in the
current cable ratings model.