On the Suitability of PLC Pulses for Power Line Fault Sensing via Time-Domain Reflectometry

This work discusses 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, we first carefully outline a TDR system operating over a power distribution network, discussing its limitations and ultimately resorting to the pulse compression procedure. Next, we present closed-form expressions for pulses and their autocorrelation functions of typical PLC modulation schemes, namely Hermitian symmetric orthogonal frequency-division multiplexing (HS-OFDM), impulsive ultra-wideband (UWB), and chirp spread spectrum (CSS). Furthermore, different metrics are used on the provided expressions in order to evaluate the suitability of the considered PLC pulses for providing proper TDR measurements, i.e., \textit{reflectograms}, in terms of resolution, effectiveness of the pulse compression, distortion, and range. Considering the scenarios of European underground low-voltage and US overhead medium-voltage power distribution networks, we finally carry out a comparative numerical analysis among the considered PLC pulses in terms of the aforementioned metrics for frequency bands comprising narrowband- and broadband-PLC, with a highlight on compliance to regulatory constraints. Based on the achieved results, we show that the use of UWB pulses allows the obtaining of a larger number of reflectograms in a given time interval, while HS-OFDM and CSS pulses provide higher reflectogram quality and better resolution for a given occupied frequency bandwidth. Also, we show 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.