Fault detection by signal response in PV module strings

A fault detection and location method in PV module strings was experimentally studied. Even if the conventional diagnosis methods such as I–V measurement or Voc measurement could find the fault existence, those methods could not locate the fault position in the string. In this paper, the time domain reflectometry (TDR), which applies the voltage signal into the string and observes the signal response waveforms, was applied to the PV strings containing faults to detect the fault and locate its position. The results showed the disconnections and the degradations with series resistance increase between modules were detected with the response signal voltage rise and the signal rise timing shift. The signal voltage rise meant the impedance change in the string and the shift meant the disconnection / degradation positions, respectively.