Application of Special Arresters on 138 kV Lines of Application Power Company
Special zinc oxide series gapped line arresters were installed on Appalachian Power Company 138 kV lines having high tower footing resistance and severe lightning exposure. This effort was part of an experiment to explore means of reducing lightning flashovers in exposed locations where low ground resistances are not feasible. Because of possible future voltage uprating of these lines, the arresters were built in the form of high strength nonporcelain mechanical struts, designed to limit phase conductor swing. This paper describes the field installation of these experimental arresters and their instrumentation and reports operating experience in 1983.
New type lightning protection schemes of substation incoming lines and their simulations
Lightning failures on incoming lines have serious impact on the safety of power substation. In some mountain areas, where the lightning activity is strong and the soil resistance is high, it is difficult to have its enough efficiency in taking traditional protective measures against lightning discharges. Two new protection measures of incoming lines are proposed and analyzed in this paper: line ZnO arrester and coupling grounding wire. Rationally installed ZnO arresters brings about both safety and economical effect on the protection of incoming lines. The coupling grounding wire is installed under the phase conductor. The electromagnetic coupling effects are improved because of coupling ground wire. The electromagnetic transient calculations are made to analyze these two measures' protective effects. According to the results of simulation, the over-voltage on the equipments is reduced significantly with the installation of line arrester. And the coupling grounding wires improve lightning protective level effectively. The computational methods are introduced and the results are compared.
Experimental energy barriers to anions transporting through nanofiltration membranes.
Environmentally relevant contaminants fluoride, chloride, nitrate, and nitrite face Arrhenius energy barriers during transport through nanofiltration (NF) membranes. The energy barriers were quantified using crossflow filtration experiments and were in the range of 7-17 kcal·mol(-1), according to ion type and membrane type (Filmtec NF90 and NF270). Fluoride faced a comparatively high energy barrier for both membranes. This can be explained by the strong hydration energy of fluoride rather than other ion properties such as bare ion radius, fully hydrated radius, Stokes radius, diffusion coefficient, or ion charge. The energy barrier for fluoride decreased with pressure, indicating an impact of directional force on energy barriers. The influence of temperature-induced pore radius variability and viscosity on energy barriers was considered. The novel link between energy barriers and ion properties emphasizes the importance of ion hydration and/or partial dehydration mechanisms in determining transport in NF.