Research Of Numerical Simulation Of Cathodic Protection System

Comparative analysis was given by measurement results and simulation which associated finite element software ANSYS with electrochemical polarization. A variety of factors such as boundary selection, medium-electric resistivity, boundary conditions of cathode and anode, power source etc were considered to the calculation of potential distribution.Generally, the region of calculation should be finite while FEM was used. Cathodic protection systems of buried pipelines or dipped-water pipelines are infinite formed by media at depth direction and at the surface where pipelines are except for areas formed by air above ground or water surface. The calculation refered to boundary selection. If we choosed small boundary, calculation may be quite different from actual distribution. But, if we choosed large boundary,we wasted machine-hour and should prepared for the lack of memory. So, we should make a comprehensive consideration on calculation cost and calculation accuracy. A research was carried on to estimate how did relative depth, relative width and relative length influence the polarization distribution under the condition that medium-electric resistivity,caliber and distance between cathode and anode were unchangeably. Meanwhile, influences of resistivity, caliber and distance between cathode and anode to the boundary selection were taken into account in this article. The results showed that with the increasing of relative depth and relative width, potential of pipe surface that near anode increased but that far from anode decreased. The potential of entire pipe surface became uniformity, which approached to the real distribution. Whereas, the influence of relative length can be ignored. Critical size of boundary selection can be small in the moment that medium-electric resistivity increased, caliber increased or distance between cathode and anode decreased.Besides breakage rate of pipeline coating, media environment and distance between cathode anode can influence the potential distribution of pipeline surface for cathodic protection system of long-distance pipeline. Potential of pipe surfaces became uniformity and had a better protection while coating breakage rate decreased, medium-electric resistivity decreased and distance between cathode and anode increased. Meanwhile, pipe diameter increased, potential distribution became positive and more uneven.Pulsating direct current is usually set as the source of current of cathodic protection in order to save energy resource or get further emission of power line. The results showed that with the increasing of frequency of pulsating direct current, site that far from anode received more cathodic current and potential distribution became more uniform. The crevice dimensions influenced medium loop resistance a lot. Crevice resistance decreased while slit width increased. Resistance along pipe length increased while distance between baffle and pipe decreased. Potential of site directly facing the crevice had a large decrease. Simulation result of actual cathodic protection system reached a good agreement with measured results except there was a few difference of value in some site...