Power line sensing via power line communication-based time-domain reflectometry

Abstract

This thesis starts with a discussion on the suitability of typical power line communication (PLC) pulses for fault sensing in power lines via pulse-compression time-domain reflectometry (TDR). For this purpose, a TDR system is carefully outlined, discussing its limitations and ultimately resorting to pulse compression. Next, closed-form expressions for pulses and autocorrelation functions of typical PLC modulation schemes are presented. Furthermore, the suitability of the considered PLC pulses for providing proper TDR measurements is discussed in terms of resolution, effectiveness of the pulse compression, distortion, and range. In sequel, key characteristics and limitations of TDR systems based on the Hermitian symmetric orthogonal frequency-division multiplexing (HS-OFDM) scheme for power line sensing are discussed. In this sense, a HS-OFDM based TDR system is outlined. Next, pulse compression and channel estimation reflectogram processing approaches are carefully described and the effects of TDR system parametrization and multiple access schemes on the HS-OFDM-based TDR system performance are addressed. Finally, a TDR system based on the orthogonal chirp-division multiplexing (OCDM) scheme is proposed for power line sensing. After the system model description, a multiple access scheme that exploits the convolution theorem of the modified discrete Fresnel transform for enabling distributed reflectometric and transferometric power line sensing is introduced. A comparative numerical analysis among the considered PLC pulses is carried out for frequency bands comprising narrowband (NB)- and broadband (BB)-PLC. First, PLC pulses are compared in terms of number of obtained reflectograms over time and reflectogram quality. It is shown that NB-PLC pulses are suitable for most distribution network scenarios, being the use of BB-PLC left for cases where very fine resolutions are desired. Further numerical analyses are then presented for supporting the carried out discussion on multicarrier TDR systems based on both HS-OFDM and OCDM schemes. It is shown that channel estimation outperforms pulse compression for HS-OFDM-based TDR systems. A comparison among the OCDM- and HS-OFDM-based multiple access schemes is then performed. Numerical results show that the proposed OCDM-based multiple access scheme achieves the highest number of measurements over time, besides yielding the same range resolution as the HS-OFDM-based counterparts. Finally, the proposed OCDM-based multiple access scheme is slightly outperformed by the HS-OFDM based on code-division multiple access and by the HS-OFDM based on frequency-division multiple access at some power line modems consisting the distributed sensing system in terms of signal-to-interference-plus-noise ratio (SINR).