Design And Application Of On-line Temperature Monitoring System For Power Cable

In recent years,in order to meet the growing demand for electricity load,the proportion of power cables in the construction of urban and rural power grids has increased dramatically,which leads to the dramatic increase of the difficulty and workload of the power cable detection and maintenance.In the large metallurgy,chemical industry,power plant,substation and other enterprises,as the improvement of the level of automation and the increase of electricity load,the number of cable in use is larger and larger.A large number of cable are set in the long and complicated cable trench.Under the consideration of long time operation of these cables in the high voltage and current environment,it is likely to cause the rise and abnormal of the temperature,which may result to the cable joint explosion and fire.In this paper,the design process of software and hardware for a cable temperature monitoring system is introduced.First of all,the method of temperature measurement and temperature monitoring system are discussed.At present,the domestic and international general conductor temperature acquisition technology can be divided into two categories,contact temperature sensing technology and non-contact temperature sensing technology.Point type temperature sensor,line type temperature sensor,optical fiber sensing technology and on-line monitoring technology of power cable based on the thermal effect,considering the spot temperature sensor has general applicability,and low cost,easy popularization through the comparison of several of the above sensing technology analysis,this paper focuses on the spot temperature sensor.The design of the whole system consists of a PC microcomputer technology as a host computer,a MCU as the lower computer to collect multi-point temperature data,the system is based on the distributed-coordinated idea and the concept of the circuit testing system of multi-point temperature acquisition.The temperature is transmitted to the main control PC for data integration processing,and the lower computer can also operate independently to monitor the distribution points of temperature acquisition points.Secondly,the hardware and software of the system are designed in this paper.The main part of the hardware circuit CPU selects AT89S52 microcontroller.Temperature detection uses DS18B20 chip,which sends the temperature to CPU(AT89S52).CPU accepts the data of DS18B20,and sends the data to ZLG7290 chip,which can be digital displayed.CPU alarm processing program,the temperature will be accepted,and set the maximum and minimum values of the data,the temperature range of the limit,it starts after comparison if the data is off the range.Digital tube display data presentation,number of temperature can be controlled by a small keyboard.The lower computer program will realize the function of hardware,and arrange the monitoring software and each executive module scheduling reasonably,the main program calls 5 sub procedures: digital display procedure,keyboard scanning and key processing procedure,temperature testing procedure,interrupt control procedure,MCU and PC serial communication procedure.As writing the main program,it only needs to call the sub procedures,and then make adjustments on the allocation of the register which works on eliminating the conflict between the I/O.The program should use as many instructions as possible instead of the jump instruction.The PC is designed of the intelligent algorithm of BP neural network,and the temperature of power cable conductor is calculated by the environmental temperature and the temperature of cable skin.The algorithm is feasible through training and verification.Finally,the paper debugs and applies the system,summarizes the announcements of the system.