Numerical Calculation Of Cathodic Protection Potential Distribution On Pipelines Between Well And Metering Station

In the design of cathodic protection system of pipelines,one of the important exemplifications of cathodic protection results is cathodic protection potential distribution.Therefore,it is very important to grasp the potential distribution of pipelines.Because of the poor reliability and poor economic security of teaditional calculation method,numerical calculation method has been widely used in the field of corrosion.Cathodic protection results can be accurately predicted using numerical calculation method,so it can be used to choose cathodic protection parameters at the initial stage of the design of cathodic protection system.It can also be used to solve the "under-protection" and "over-protection" problems which occur during the operation of the cathodic protection system.Therefore,numerical simulation technology about cathodic protection of the gathering and transportation network can provide theoretical guidance for the design,construction,measurement and maintenance of cathodic protection.In this paper,firstly the physical model about cathodic protection potential distribution of pipelines is obtained by simplifying actual cathodic protection system.Then,the control equation of constant electric field potential distribution is deduced according to the basic theory of electrostatic field.Poisson equation is used as the governing equation of this model.At the same time,the boundary condition of the model is determined according to the actual situation.In resolving the governing equation,firstly,boundary integral equation is deduced based on the Green's formula.At the same time,the boundary is discreted by boundary element method and mirror method.Tube unit is used as discrete element,and each unit is regarded as constant unit,and then the discrete equations are obtained.Then,potential distribution on the pipelines is obtained by processing coefficient matrix,auxiliary anode parameters,and cathodic polarization curve.Finally,the calculation program of potential distribution on pipelines is written using MATLAB software.The cathodic protection experiment system is designed indoor,and cathodic protection potential of pipelines is measured by power cut method.At the same time,under the same experimental parameters,potential distribution of pipeline cathodic protection is simulated by Beasy software.Finally,the correctness of MATLAB program is proved by comparing the results obtained in three ways.Then,the experimental system is used to study potential distribution of pipelines in different anode positions of single pipeline,different anode positions of two pipelines and different angles of two pipes.Models are built under conditions involving single pipeline and two pipelines.Numerical calculation is carried out to study the influence of the length of anode,soil resistivity,distance between anode and pipeline,depth of anode,anode current output,angle of two pipelines and etc.on cathodic protection potential of pipelines,and a relationship is attained ultimately.