System Maintenance & Troubleshooting Flashcards

A string of PV modules shows significantly lower output than adjacent strings on the same array. The first diagnostic step should be to:

Answer: Measure open-circuit voltage (Voc) of each module in the string

Measuring Voc on each module individually isolates whether the issue is a single failed module, partial shading, or wiring fault.

During routine maintenance, a technician finds that an inverter's ground fault protection device (GFPD) has tripped. The safest next step is to:

Answer: Disconnect the array and inverter, then inspect wiring for ground faults before resetting

A tripped GFPD indicates a real or suspected ground fault; the system must be de-energized and inspected before resetting to prevent fire or shock hazard.

Which condition is MOST likely indicated when infrared thermography reveals a hot spot on a single cell within a PV module?

Answer: Cell crack, delamination, or bypass diode failure

Localized hot spots on individual cells typically indicate physical damage such as cracks, delamination, or a failed bypass diode forcing current through a resistive cell.

A battery-based off-grid system shows that batteries are consistently undercharged after several sunny days. The MOST likely cause is:

Answer: Charge controller set-point voltage too low for battery chemistry

If the charge controller's absorption or float voltage set point is lower than the battery manufacturer's specification, the batteries will never reach full state of charge.

When performing IV curve tracing on a PV string, a 'stepped' curve with multiple knee points most likely indicates:

Answer: Partial shading or module mismatch within the string

Multiple inflection points on an IV curve are characteristic of partial shading or module mismatch, where bypass diodes in some modules are conducting.

A grid-tied inverter repeatedly disconnects and reconnects throughout the day. Utility voltage logs show voltage rising above 253V (120% of nominal 211V) during peak generation hours. The BEST corrective action is to:

Answer: Work with the utility to address the voltage rise issue or reduce array output via curtailment

Overvoltage on the utility side is a grid-interaction issue; the solution involves utility coordination for voltage regulation or implementing Volt-Watt curtailment, not raising trip thresholds beyond safety limits.

What is the primary purpose of performing a 'tug test' on module mounting hardware during a maintenance inspection?

Answer: To confirm that racking connections and fasteners are properly torqued and secure

A tug test physically verifies that clamps, bolts, and racking connections have not loosened due to thermal cycling, vibration, or corrosion.