Atti dell'8º forum nazionale delle misure

This paper presented the development and characterization of a PLC coupling system, based on the use of capacitive dividers embedded in commercial cable separable connector (SC) of MV cables heads. The new SC-based coupling solution is aimed at providing a possibility of exploiting a different electrical element installed in secondary substations for PLC signal coupling, when VDS is not available, so to reduce costs for signal coupling equipment. The research work explored the possibility of using the proposed coupling solution to transmit PLC signal in accordance with IEEE STD 1901.2-2013, evaluating the communication success rate with different modulations and center frequencies; in detail the attention was focused on OFDM modulation in the FCC above CENELEC frequency band, i.e. between 154.6875 and 487.500 kHz. Moreover, two cases were analyzed, i.e. OFDM signals with 18 or 36 sub-carriers. To design the coupler, commercial SCs were characterized by using impedance measurement at all terminals and a circuital model was obtained. An ad-hoc electronic board was designed with adjustable parameters. The board was appropriately sized to maximize performance in MV. The designed interface board was built and tested in laboratory. A dedicated test bench was set up to evaluate the performance of the system. First, frequency response tests were performed. It was shown that it is possible to obtain a very flat frequency response in the case of signals with a bandwidth of 80 kHz. In detail, it was shown that it is possible to establish effective communication with the SC with high values of success rate while maintaining a high SNR; it was also possible to communicate with 18 subcarriers even 8-PSK type modulations in all ranges. Measurements with 36 subcarriers showed that it was possible to communicate with high success rates up to QPSK, while only at higher frequencies could 8-PSK modulated signals be received correctly.. The proposed SC based solution, together with the previous developed by the authors for VDS installed in the MV switchgears of distribution network’s substations, confirm the feasibility of coupling PLC signal by means of elements already installed in MV networks thus reducing cost of installations of dedicated PLC couplers.