Measurement and modelling of pitting depth distribution for phosphor bronze tapes used in underground power transmission cables

Phosphor bronze tapes used in underground power transmission cables are affected by pitting corrosion that can lead to cable failures. In the present work, the probability distribution of corrosion pit depth on phosphor bronze tape is investigated by using Monte Carlo simulations and compared with the measured pit depth distribution of such tapes which have been in service for about 45 years. The pit depth as a function of time is modelled as 𝑦(𝑡) = 𝛼(𝑡)^𝛽 where y is the pit depth, α and β are pitting proportionality and exponent factors. A Monte Carlo simulation is performed to generate the pit depth distribution by keeping β as constant and varying α using three parameter Generalized Extreme Value (GEV) distribution. We observed that the simple power law is capable of predicting the evolution of pit depth distribution and also the distribution under different environmental conditions. This predictive pit depth distribution model will be a valuable tool to decide the extent of pitting corrosion in phosphor bronze tape used in underground power transmission cables.