When measuring the open-circuit voltage (Voc) of a PV string, the measured value is lower than the temperature-corrected expected value. What is the most likely cause?

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Multiple choice — select the best answer

AThe string has more modules than designed
BOne or more modules in the string are bypassed or shaded
CThe irradiance is higher than STC
DThe inverter MPPT voltage is set too high

✓ Correct answer: B. One or more modules in the string are bypassed or shaded A string Voc lower than expected typically indicates a module is being bypassed (by its own bypass diode due to shading or damage) or a module is missing from the string, reducing the series voltage.

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Topic: Commissioning & O&M

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When measuring the open-circuit voltage (Voc) of a PV string, the measured value is lower than the temperature-corrected expected value. What is the most likely cause?

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