Research On On-line Monitoring System For Power Cables Based On Metal Shielding Layer Carrier Communication

With the development of China’s urbanization process, the proportion of underground power cable in transmission and distribution lines is increasing. Cable fault may cause huge economic losses to the enterprise and society, even the casualties. Therefore, monitoring state of cable, preventing cable fault, has theoretical value and practical significance. Due to favorable electrical properties, crosslinked XLPE power cable is welcomed by masses of users. Its manufacturing technology is becoming mature, gradually develop to the field of high voltage and extra high voltage, it’s proportion in the urban’s power transmission and distribution network is growing and has presented the tendency of alternative oiled paper insulated cables.Power line carrier communication uses power line as communication medium, has the advantage of less investment, wide scope of coverage, need not extra wiring, easy to expand and transform, is widely used in electric power communication network. The traditional power line carrier communication uses electric power lines as the channel, make use of power cable metal shielding layer for carrier communication is a new technology developed in recent years, has became a research hotspot in the electric power and other relevant institutions at home and abroad, it is successfully used in the urban communities’ distribution automation.This paper use Matlab program for simulating power cable metal shielding layer of carrier communication system. Through simulation, get the results of changes of the waveform and the bit error rate curve of each node during the transmission of the source in the model. And use crosslinked XLPE power cable as the research object, take advantage of metal shielding layer of cable as communication channel, base on power line carrier communication technology, build on-line monitoring system of power cable, design hardware circuit and do relevant experiments. The main research content are as follows:Firstly, introduce each layer’s structure and function of crosslinked XLPE power cable, analyse transmission characteristic and noise environment of metal shielding layer channel,introduce modulation and demodulation technology commonly used in the power line carrier communication. Secondly, use Matlab program for analyzing shielding layer communication system, adopt 2FSK and DSSS technology respectively, design six kinds of simulation models, analyse the signal changes in the process of transmission, obtain bit error rate curve of models. Once more, design on-line monitoring system hardware circuit of power cable, including power circuit, signal acquisitioin circuit, signal processing circuit and signal display circuit, etc. Then, design software programs of on-line monitoring system of power cable, including two parts of lower computer system software and upper computer system software. Finally, debug module and overall test the designed on-line monitoring system, measure experiment waveform, analyse experimental data. The experiment results show that, this system has simple connection, low hardware cost and good monitoring result, it’s suitable for the occasion of signal transmission for underground power cable and submarine power calbe without composite optical fiber communication in the early days. This paper’s studies has certain reference value for on-line monitoring of power cable and urban districts’distribution autiomation.