Modelling the tape corrosion process for oil-filled underground cables
National Grid Electricity Transmission
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Network Innovation Allowance
The conventional sampling method (currently adopted by National Grid) is a phenomenological one which is far from optimised. On the other hand, research in mechanics of materials has provided a solid understanding and large amount of data for corrosion fatigue. The factors that control corrosion fatigue of the tin bronze tapes include the oil pressure, temperature and its range of change (caused by change in loading), and the environmental factors of the cable’s laying environment, such as the presence of ammonia, chloride, sulphur and moisture. This project will enable National Grid to take these controlling factors into account in the life prediction and sampling strategy. There are five milestones in the proposed project: a) the dominant failure mechanism of the reinforced tape is confirmed; b) the empirical and mechanism-based models for calculating (cross-reading) cable condition and remaining life are identified; at the same time c) a database for nominal input data from literatures including environmental corrections is setup; d) a sampling strategy is established, and e) National Grid’s specific data to refine the modelling accuracy is included.
- Confirm the dominating mechanism leading to tape failure and consequent oil leak
- Develop a computational (cross-reading) method for calculating residual life before failure
- Identify input parameters required by the computational method from data of leak and non-leak case studies, history of oil pressure, temperature and temperature change environmental variables
- Quantify the risk of using nominal data and mechanism-based models in the life prediction
- Develop a database of input parameters for the computational model from both the research literature and the National Grid reports and database.
- Practical risk mitigation recommendations regarding to cable tape corrosion
- Quantitative understanding on the mechanisms of tape failure
- Innovative methodology and framework for cable condition assessment
- A deterioration model able to capture the dominant mechanisms of the tape corrosion problem
- Database which provides key input for the model
- Sampling and decommissioning strategy which will enrich the database
- Risk mitigation recommendations based on understanding the dominant mechanisms of corrosion