Copper sulphide long term mitigation and risk assessment

Summary

This TB describes mechanism of copper sulphide formation, provides guidelines for risk assessment and recommendations to network owners and operators how to manage power transformers with sulphur corrosion problems. A number of failure cases caused by sulphur corrosion, i.e. deposition of metallic sulphides in transformer active part are described in TB, together with failure cases statistics. Main mitigation techniques applied to reduce or eliminate risk of transformer failure induced by sulphur corrosion are: addition of metal passivator, oil change and treatment of the oil to remove reactive sulphur species. Effectiveness, side effects and drawbacks of these mitigation techniques are described, together with results of mitigation survey. Cost-effective risk mitigation strategies and recommendations for mitigation in relation to transformer condition assessment are provided in this TB.

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