CSLB C-46 Solar ContractorPhotovoltaic System InstallationEasy
A solar technician is performing a ground fault test on a DC PV array. They measure the resistance between the positive DC conductor and ground, and then between the negative DC conductor and ground. Both readings show a very high resistance (e.g., >1 Mohm). What does this indicate?
- AThe insulation of the DC conductors has failed completely.
- BThe PV modules are not producing power due to low irradiance.
- CThe PV array is properly isolated from ground, indicating no ground fault.
- DA severe ground fault is present, requiring immediate shutdown.
Show answer & explanationAnswer & explanation
Correct answer: C. The PV array is properly isolated from ground, indicating no ground fault.
A high resistance reading (ideally infinite, but practically very high like >1 Mohm) between any current-carrying conductor and ground indicates good insulation and proper isolation. This means there is no unintended current path to ground, which is the definition of a healthy system without a ground fault.
Why the other options are wrong
- A. Failed insulation would result in low resistance readings to ground.
- B. Irradiance affects power production, not the insulation resistance to ground.
- D. A severe ground fault would show very low resistance, indicating a direct path to ground.
PV Ground Fault Detection (Insulation Resistance Test)
A test to measure the electrical resistance between current-carrying conductors and ground to ensure proper insulation and detect unintended current paths.
- High resistance (e.g., >1 Mohm) indicates healthy insulation.
- Low resistance indicates a ground fault.
- Crucial for safety and system performance, preventing shock hazards and equipment damage.
Memory trick: High resistance, no ground fault; low resistance, then halt!