Research On The Heating Mechanism And Temperature Rise Monitoring System Of Underground Power Cable

How to make the power cable in urban city improve their overall transmission capacity under the precondition of not largely increas ing the number, is not only an important task for urban planning, but also an important issues which is urgent to solve to the whole power system research. Under the circumstances of no external damage, power cable service life is largely dependent on the cable temperature during the daily operation. The power cable under high load operation, which will be at a high temperature, not only harm to its operation life, but also cause extreme explosion accident when it is serious. This paper research a variety of factors which cause the underground power cable overheating, based on the two aspects of the heating production and dissipation during the daily operation. And design a buried power cable temperature monitoring system based on the mechanism in the research.First of all, this paper studies the cable temperature and capacity in IEC60287. The conductor loss, insulation dielectric loss, metal sheathing loss and armored layer loss calculation method is applied in this paper for the study of heating cable: they all can be as the inter nal heat source of the heating cable. In the aspect of heat dissipation, the dissipation path of the buried cable is studied, and the finite element analysis method is introduced to analyze the heat dissipation of buried cable. Through a calculation example, the calculation process of various losses of a certain type of cable is given.Secondly, for the common two buried cable laying method in engineering: in soil and in drainage pipe laying finite element simulation modeling are build. Simulation model is applied on the load for the cable conductor loss and dielectric loss, metal sheathing loss and armored layer loss. Several factors affecting the heat production and dissipation of the cable are analyzed: the distance between the cable, the cable current, the buried depth, the heat transfer coefficient of the soil and the air temperature. Then the mechanism of the factors is obtained. The steady state and transient state of the cable are analyzed respectively. The BP neural network is applied to predict the temperature of power cable, after the random samples of training and testing, the temperature prediction results appeared to be good.Finally, the temperature rise monitoring system of underground power cable is set up. The hardware of the system adopts the "HKA-D series of distributed optical fiber sensing measurement analyzer" of one company in Shanghai. Measure and process the cable temperature by using the distributed optical fiber temperature sensor. The temperature rise monitoring system of underground power cable is different to previous cable temperature on-line monitoring system, in addition to the conventional basic function such as cable temperature real-time acquis ition and display, historical trend display, add the additional function that use the current values and the air temperature values to predict the temperature of cable, and alarm SMS message prompt function. The forecast function is based on the analysis of the cable temperature field simulation data, using BP neural network to realize the function of the unknown temperature prediction. The software part use the force control configuration software to build, and use OPC communication for real-time communication between configuration software force control and data analysis software MATLAB, the neural network to cable temperature prediction function is embedded to the configuration interface.