NABCEP System Maintenance & Troubleshooting 4

Question 1

A soiling loss study on a utility-scale PV plant shows a 3% monthly energy loss. The O&M team wants to determine the optimal cleaning frequency. This decision should primarily be based on:

Accepted Answer

A cost-benefit analysis comparing cleaning costs against the value of recovered energy

Answer

The economically optimal cleaning interval is determined by comparing the marginal cost of cleaning against the marginal revenue from recovered energy production.

Question 2

While measuring insulation resistance of a PV array with a megohmmeter (megger), a technician should test at a DC voltage that is:

Accepted Answer

At least equal to the maximum system voltage rating per NEC and the instrument manufacturer's guidance

Answer

Insulation resistance testing must be conducted at a voltage level appropriate for the system's maximum rated voltage to stress-test the insulation adequately per NEC and IEC standards.

Question 3

An MPPT charge controller in a PV-battery system continuously operates in bulk charge mode and never transitions to absorption. The MOST likely cause is:

Accepted Answer

PV array is undersized relative to battery bank capacity, and charge current is insufficient to raise battery voltage to the absorption set point

Answer

If the array's available current is too small relative to the battery's capacity, the battery voltage may never rise to the absorption set point, keeping the controller in bulk mode.

Question 4

A PV module with a failed bypass diode that is NOT conducting will cause which condition during normal operation?

Accepted Answer

The affected cell group will develop excessive heat as a hot spot, potentially damaging the module

Answer

A non-conducting (open) bypass diode means shaded or underperforming cells must pass full string current, dissipating power as heat and creating damaging hot spots.

Question 5

When inspecting conduit runs during a maintenance visit, a technician finds conduit fill has increased due to an added circuit by a previous contractor. The primary concern regarding NEC compliance is:

Accepted Answer

Whether total conductor cross-sectional area exceeds the NEC Chapter 9 conduit fill allowance

Answer

NEC Chapter 9 limits conduit fill to protect conductors from overheating and facilitate pulling; exceeding the fill limit is a code violation requiring larger conduit or separate raceway.

(NABCEP) Certified North American Board of Certified Energy Practitioners Specialist Practice Test

(NABCEP) Certified North American Board of Certified Energy Practitioners Specialist Practice Test

NABCEP System Maintenance & Troubleshooting 4