Question 1

What does an IV curve tell you about a solar PV module or string?

Accepted Answer

An IV curve plots current against voltage across the full operating range of the module or string, from short-circuit current (Isc) at zero voltage to open-circuit voltage (Voc) at zero current. The shape of the curve reveals shading losses, soiling, cell degradation, bypass diode faults, series resistance increases, and mismatch — defects that a simple Voc or Isc measurement cannot distinguish.

Question 2

What equipment do I need to trace IV curves on a solar string?

Accepted Answer

You need a dedicated IV curve tracer rated for your system voltage (1000 V or 1500 V DC) and capable of sweeping through the full current range of your string. Suitable instruments include the Sonel PVM-1530, Emazys Z300 HE, Entec E-1500, and Sonel IRM-1. A calibrated irradiance and temperature reference sensor is also required for translation to STC.

Question 3

When should IV curve tracing be performed on a PV system?

Accepted Answer

IV curve tracing should be performed at commissioning (IEC 62446-1 Category 2 baseline), after any significant fault event, during periodic O&M inspections where underperformance is suspected, and following module replacements to verify string consistency.

IV Curve Tracing

IV Curve