Evaluation System Design On Real-time Dynamic Ampacity Of Soil Buried Power Cables

Direct buried is one of the main ways which power cable is laid.The ampacity of power cable is an important parameter in design and operation.Too large ampacity designed will reduce the power cable lifetime,on the other hand,too conservative ampacity designed will increase the investment of cable.Power cable amapcity is closely related to the environment,and because of the real-time dynamic change of the parameter of environment,it becomes more important to accurate evaluate the real-time dynamic ampacity.Through the research of the evaluating methods and the real-time environmental parameter monitoring,this paper builds an evaluating system about the real-time dynamic ampacity of the soil buried power cable.This system monitors,transmits and displays the environmental parameters.By using the software,this system completes the calculation of the ampacity.The conclusion plays a guiding role to improve the efficiency and reliability of the power cable.The main research work of this paper is as follows:By using Bessel function,the paper establishes the calculation model of the electromagnetic loss of the direct buried power cable,and calculates the electromagnetic loss of the cable cores and metal sheaths.Based on C language,GPRS modules,STM32F4 demoboard and a variety of sensors are used to design the real-time monitoring system to collect and transmit the real-time environmental factors' datum,such as temperature,humidity,wind speed and intensity of illumination.By comparing the results of the heat pipes test with the finite element calculation,the paper proves that the finite element method is effective in calculation of temperature field of the direct buried power cable.Combined with the finite element method and iterative method,the paper provides the evaluating design of the real-time ampacity by using the real-time monitoring system of environmental factors.This assessment provides the theoretical support for the whole evaluating system.By using VB and the finite element simulation software ANSYS,the paper designs a evaluating system of the real-time dynamic ampacity which calculates the cable ampacity,and also monitors,transmits and displays the environmental parameters.By analyzing factors which affect the ampacity of direct buried power cable,such as the air temperature on the surface,backfill,arrangement and grounding mode,the number of loop,thermal resistance coefficient of the soil,deep,loop spacing,the paper draws the conclusion which provides beneficial suggestions to improve the efficiency and reliability of the power cable.