Measurement of Differential Mode Impedance and Longitudinal Conversion Loss for In-Factory High-Speed PLC System using Three-Phase Power Distribution System

The differential mode impedance (DMZ) and the longitudinal conversion loss (LCL) are important parameters to introduce high-speed power line communication (PLC) systems. Therefore, we should evaluate the DMZ and LCL in a factory environment because the three-phase power distribution system has been employed in factories. The admittance matrix elements at the power distribution board were determined from S-parameter measured with a vector network analyzer. An isolation probe was developed to measure S-parameters under high voltage applying conditions. Measurements were carried out at 60 points in 4 factories. The admittance matrix was represented by the equivalent circuit composed by six impedances, then the DMZ and the LCL were calculated from the mean value of the impedances. The results showed that the absolute value of DMZ was lower than the characteristic impedance of the PLC transmission line, and the LCL value was similar to the LCL in house environment where a two-phase power distribution system was employed.