Mechanism of saline deposition and surface flashover on outdoor insulators near coastal areas part II: Impact of various environment stresses

This is the second in a two-part paper series dealing with sea salt transportation and deposition mechanisms, and discussing the serious issue of degradation of outdoor insulators resulting from various environmental stresses and severe saline contaminant accumulation near the shoreline. The deterioration rate of outdoor insulators near the shoreline depends on the concentration of saline in the atmosphere, influence of wind speed on the production of saline water droplets, moisture diffusion and saline penetration on the insulator surface. This paper comprises two parts. The first part, deals with the impact of different environmental stresses on insulator surface degradation, including wind speed and direction, cold fog and rainfall. The second part concerns the flashover process related to saline contamination of the surface under constant and variable cold fog wetting rates and equivalent salt deposit density (ESDD). The experiments were performed on high voltage insulators based on the model presented in Part-I. Based on the proposed model, the influence of wind speed and direction on the pollution accumulation rate and impact of wetting rate on discharge current and surface flashover process were investigated. The equations S=S
₀
e
^(Vdep0/αh)
[e
^(-αx/v)-1
] and D=D
₀
e
^(Vdep0/αh)
[e
^(-αx/v)-1
] are derived from the model for saline concentration and deposition show good reliability and well represent the results obtained. Test results also show that due to the different wetting and contamination deposition rate, surface discharge current characteristics of tested insulator in rain are different with that in cold fog, which lead to different surface flashover voltages. An experimental setup was mounted for artificial saline contamination deposition. The proposed model can be therefore used to investigate insulator flashover near coastal areas and for mitigating saline flashover incidents.