Research And Application Of Low Voltage Power Line Carrier In Electric Energy Meter Reading System

Low voltage power line carrier communication utilizes the existing distribution lines to transmit communication signals,which needn't to invest and build special communication channels.It has the advantages of high mechanical strength,good reliabilityand maintenance free.With the construction of the "three sets and five big" strategic for the national grid and the popularization of the regulation "one household and one table,the meter reading to the household",the intelligent meter reading technology with the power line carrier as the main communication carrierhas been widely used,which greatly improves the service quality of the power company,reduces the line loss,produces huge social benefits and economy benefit.However,the power line is designed for the low loss transmission of 50 Hz or60Hz alternating in the recent time.It does not have the necessary conditions for satisfying the symmetry and uniformity of the ideal communication channel.At the same time,the power line channel is an open channel,and the random access and disconnection of various electrical devices are produced by the impedance mismatch,noise interference,and noise interference.The problem of electromagnetic interference is very serious,which results in a relatively large attenuation range.On the power line,the transmission of different frequency signals is different,and the channel obviously shows the frequency selection characteristics.With the different load conditions,the power line channel presents obvious time-varying nature,which increases the complexity of communication environment.Therefore,in-depth research on the channel characteristics of low-voltage distribution lines is the key to improve the quality of low-voltage power line communication.This paper mainly investigates the input impedance characteristics,channel attenuation characteristics and noise characteristics of high frequency(1MHz~30MHz)power line channel in three aspects.(1)This paper introduces the influence factors of the low voltage distribution network structure and the characteristics of the high frequency impedance change of the circuit components.According to the transmission line theory,the line impedance and the input impedance characteristic model of the low voltage distribution network isestablished.Then,the actual measurement of the input impedance and the residential area is selected in the laboratory.The same distribution line is simulated by Matlab and the input impedance characteristics are compared and analyzed by themeasured data of distribution line parameters.(2)The spatial variation of current traveling wave and voltage traveling wave under the high frequency signal is analyzed by the transmission line theory.On this basis,the time domain model and frequency domain model of the high frequency signal of the distribution network are established,and the attenuation degree of the representative different distribution network environment measurement signals is selected.Finally,the laboratory simulation verification of the measurement results are obtained.(3)According to the source of the noise,the characteristics are classified.Through the actual measurement of the noise of the distribution lines,the complex noise in the field environment can be simulated by a variety of basic noises,and the noise of the low-voltage power line is analyzed by computer simulation.Finally,the organizational structure and function expansion of the power line carrier meter reading system are introduced,and the advantages and characteristics of the system are briefly analyzed.