Transformer Oil Passivation and Impact of Corrosive Sulphur (TOPICS)
National Grid Electricity System Operator
National Grid TO Innovation Team
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Innovation Funding Incentive
Gas Distribution Networks
Formation of corrosive sulphur in oil and subsequent copper sulphide deposition
in paper has led to a number of large transformer failures worldwide. It was the
cause of the failure of Lackenby SGT4 and other transformers will be removed
from the system early because the problem is believed to be advanced.
Part of the complex process leading to transformer failure involves the
mobilisation of copper containing material into the paper insulation surrounding
the windings, which is known to be influenced by the presence of corrosive
sulphur species in the oil, and extreme operating conditions.
Although there have been many attempts to better understand the mechanism
by which formation of copper sulphide occurs none have yet been conclusive.
They have not led to sufficient understanding to allow diagnosis of the problem
without inspection and better mitigation methods may still arise if the mechanism
is better understood.
The key objective of this project is to reduce the risk of transformer failure and
unreliability resulting from corrosive sulphur in oil.
This key objective will be met by:
- Better understanding of the mechanism by which copper sulphide failures
occur and the effectiveness of passivation
- Fully understanding the effects, both chemical and electrical, of passivation
on transformer insulation performance
- Investigating the reasons for silver corrosion in tap changers and to
formulate monitoring/assessment strategies in order to provide a measure of