Basic Research On Cathodic Protection Output Adjustment Of Underground Pipeline Under Disturbance

As a simple and easily-operated protection method, Impressed Current Cathodic Protection is being wildly used. Particularly in combination with the coating protection method, it can greatly extend the working life of buried pipeline and save construction costs. The principle and theory of Impressed Current Cathodic method is not so complicated. But involves the practical application of engineering, the usual approach is complemented of a simple calculation and adjustment attempts. Sometimes, the specific role of the environment, and time-varying changeable conditions are not so clear. The results of simple design calculation may not be applicable and exact. If the safety factor obtained is too large, it will cause unnecessary over-investment, with reduced protective effect. To make more excellent cathodic protection system operation, we should distinguish and do researches of the real impact ones in numbers of environmental factors to find the optimal working state of the system and the measures which can achieve this aim.From the above, after the study of corrosion of buried pipeline and the environmental effects, this paper will focus on the research of effect given to actual distribution of potential and current on pipeline surface by the role of stray current. And based on the work features of potentiostat, we distinction the part of stray current which reach the surface of the pipeline. We hypothetical that such part of stray current-also named plus current is from a Virtual Current Source. When it reaches the surface, it gives a polarization or depolarization effect to the pipe metal and increase or offset the protection current output by the real Cathodic protection system.Based on this increase or offset effect, the cathodic protection system output parameters should be altered. In solving the specific problem of output parameters adjustment, in the paper, based on the similarity of steady current field and electrostatic field, derivation the based mathematical model used to get potential distribution on high axisymmetric pipe surface by the Boundary Element Method (BEM)Take account of the specific role of interference current into the basic model, we can obtain the relationship between the request output elements and the actual output elements under the condition of constant surface potential distribution, we can also get the corresponding formula. In using this relationship and formula, we can finally get the output elements adjustment tendency of cathodic protection station under interference current effecting and achieve the aim of basic research.