Patent ID: 8466706

Claim:
An apparatus assembly for monitoring individual strings of series-connected photovoltaic (PV) panels that collectively form a PV array, comprising: a combiner box connected to the strings of PV panels, each of the strings being connected to a corresponding panel feed in the combiner box; a plurality of protection devices each connected to corresponding panel feed; a current source configured to inject a known current into a first of the panel feeds that receives current from a first of the strings; logic and control circuitry coupled to the panel feeds and to the current source, the logic and control circuitry being configured to: measure a voltage across a resistive element in series with the first panel feed, cause the current source to inject the known current into the resistive element responsive to a measured voltage across the first string not exceeding a predetermined minimum voltage level, calculate and store a resistance value representing a resistance of the resistive element as a function of the known current and the measured voltage; and output terminals for connection to a DC-to-AC inverter.