Quantifying the Environmental Sensitivity of SSTDR Signals for Monitoring PV Strings

Current spread spectrum time-domain reflectometry (SSTDR) fault detection methods in photovoltaics compare measurements with a fault-free baselin.Yet, environmental factors, such as illuminance, temperature, and humidity, affect these signals and can negatively affect our ability to detect and locate faults. This article explains and quantifies the effects of environmental factors on SSTDR measurements. We demonstrate that illuminance, temperature, and humidity each significantly affect reflections from photovoltaic panels, which require the use of up to 240 baselines to prevent environmental variation from obscuring faults. We present a method to determine the number of required baselines in any given climate and motivate future work in baseline prediction.