PV System Commissioning

The Tests

  • Polarity of each module string to verify that wires are marked and connected properly—check before connecting to the inverter, since reverse polarity could harm it.
  • Open-circuit voltage (Voc) to confirm that series strings are properly wired. All parallel strings’ Voc should be within 5% of each other and within manufacturer’s tolerances for the given irradiance and cell temperatures of the test conditions.
  • Short-circuit current (Isc) to confirm that all strings’ short-circuit currents are within 5% of each other.
  • Grounding continuity to verify that adequate grounding has been established by measuring the array to earth ground resistance. A very high resistance means that there’s a bad connection (for example, an improperly torqued ground screw) in the grounding system.
  • Insulation resistance testing (sometimes referred to as “megger testing”) confirms that there is no short-circuit connection between the positive and negative conductors and ground (see “Insulation Resistance” table for the pass/fail criteria and test voltages as recommended by IEC62446).
  • Performance verifications ensure that the inverter is supplying the predicted output under operation based on the irradiance, ambient and cell temperatures, AC and DC voltage drop, and the inverter’s efficiency.