How to Repair Ground Faults in PV Systems

By Will White, Fluke Senior Application Specialist, DER

A confirmed ground fault in a solar photovoltaic (PV) system must be addressed immediately. Left unresolved, it can cause inverter shutdowns, performance losses, arc faults, and even fires. Once you've located the source of the ground fault, the next step is to make safe, code-compliant repairs that restore system health and integrity.

This guide outlines the steps for repairing ground faults in photovoltaic (PV) systems using the correct tools, personal protective equipment (PPE), and proven methods. Whether you're working on a string conductor, module connector, or homerun wire, this process ensures a reliable fix.

How to Repair Ground Faults in Solar PV Systems

Step-by-Step Guide on Repairing Ground Faults in PV Systems

Step 1. Identify and Confirm the Fault Location

Use one or more of the following:

Before making any repairs, ensure that:

You've accurately located the exact fault location
Fault type (e.g., wire damage, connector failure) is visually or electrically confirmed
The system section is isolated and de-energized following lockout/tagout (LOTO) procedures

Never begin repairs until you are certain the system is off, locked out, and fault current is no longer flowing.

Step 2. Assess the Type and Severity of Damage

Ground faults can range from minor conductor abrasion to extensive insulation melt and arc flash damage. Identify:

Minor damage (e.g., a nicked wire or pinched insulation)
Connector failure (e.g., melted or loose module quick connector)
Severe thermal damage (e.g., burned conduit, blackened combiner boxes)
Structural involvement (e.g., fire-damaged modules, melted racking)

This determines the repair scope and whether replacement of modules, connectors, or wiring is needed.

Step 3. Verify the Circuit Is De-Energized

Use a live-dead-live test to verify there is no voltage or current present:

Test your meter on a known voltage source like a live circuit or a proving unit like the Fluke PRV-240.
Measure the faulted conductor or circuit segment and verify that no voltage is present.
Re-test the meter on the known voltage source to confirm meter accuracy and function.

Also, use a clamp meter (like the Fluke 393 FC, Fluke 283 FC/PV, or 325) to confirm zero current in the conductor before cutting or splicing.

Step 4. Repair or Replace the Faulted Component

A. Repairing a Damaged Conductor in Free Air

For minor damage on exposed string conductors:

Cut out the damaged section using a properly rated tool.
Strip the conductor ends.
Attach module quick connectors to each end (positive and negative) following the manufacturer's instructions.
Plug the connectors together securely.
Properly secure the repaired wire using UV-rated wire management hardware, such as stainless-steel wire clips.

Confirm the polarity and voltage of the repaired circuit before re-energizing.

B. Replacing a Faulted Conductor in Conduit

If the conductor is within a conduit:

You may need to remove all conductors to extract the damaged one safely.
Replace the damaged conductor with a new, properly rated wire of the same gauge and insulation type.
Use fish tape and pulling lubricant (if needed), reinstall the conductors in the conduit.

C. Repairing or Replacing Damaged Connectors

Use matching connector types (e.g., MC4-to-MC4).
Inspect mating connectors for burn marks, corrosion, or warping.
Cut out damaged connectors.
Replace any compromised connectors with certified, field-installable alternatives.
Verify connections with a tug test and visual inspection.

Note: PV connector manufacturers have specific training and installation requirements to ensure field-installed connectors meet their listing requirements. Be sure to follow the manufacturer's installation instructions and get the appropriate training.

D. Replacing Fire-Damaged Equipment

If the ground fault caused severe damage:

This type of repair varies significantly depending on the equipment impacted and the extent of the damage.
Replace all affected modules, junction boxes, inverters, wiring, etc.
If modules were impacted, confirm their integrity using manufacturer-recommended test methods.
If damage extended to the racking or grounding system, conduct a thorough inspection to ensure equipment integrity and code compliance. Replace damaged equipment as necessary.

Step 5. Retest the Repaired Circuit

Once the repair is complete:

Perform an insulation resistance test on the repaired conductor to ground using 500–1,500 VDC.
Reconnect the conductor to the system.
Repeat voltage-to-ground tests on the positive and negative sides of the string of modules.
Confirm that:
- String Voc is within the expected range
- Voltage to ground = 0 VDC for both the positive and negative sides of the string of PV modules
- Insulation resistance is within acceptable limits (e.g., >100 MΩ)

Document all test results for compliance and warranty purposes.

Step 6. Re-Energize and Monitor the System

After retesting, remove LOTO devices and re-energize the system carefully:

Close the AC and DC inverter disconnects following the inverter manufacturer's startup procedure.
Monitor inverter startup for fault codes
Confirm expected production in the monitoring platform
Inspect physically one final time to ensure no loose connections remain

If the inverter still shows a ground fault error, repeat the testing steps. You may have more than one fault.

Step 7. Log and Document the Repair

Maintain a record of the fault and repair:

Fault location and type (e.g., pinched conductor between module 4 and 5)
Tools and methods used
Test data before and after repair
Replacement parts (e.g., conductor type, connectors)
Date, technician name, and photos, if possible

This record supports ongoing operations, safety audits, and equipment warranties.

Prevention Tips to Avoid Repeat Faults

After repairing a ground fault, take preventive steps:

Use appropriate strain relief and UV-rated cable management
Avoid routing wires near sharp edges or moving components
Seal junction boxes against moisture ingress
Perform annual visual inspections and insulation resistance checks
Use PPE during testing—even for small systems

Prevention is always cheaper than repeat repairs. See: Why DC Ground Faults Are Dangerous

Conclusion

Repairing a ground fault in a PV system is a critical skill for solar technicians. Whether caused by wear, poor installation, or environmental stress, ground faults can pose serious safety hazards and degrade performance. With the right steps, tools, and documentation, you can complete a safe and effective repair and keep the system running smoothly.

About the Author

Will White began working in solar in 2005 for a small integrator. After starting as an installer, he worked in sales, design, and project management, and he eventually became the Director of Operations. In 2016, he joined the curriculum team at Solar Energy International (SEI), where he focused on developing course content and teaching solar classes. In 2022, Will moved into a solar application specialist role at Fluke, where he supports their renewable energy testing equipment like IV-curve tracers, electrical meters, and thermal imaging cameras.

Will has experience in wind power, solar thermal, energy storage, and all scales of PV. He is passionate about implementing high-quality, code-compliant installation techniques. Will has been a NABCEP Certified PV Installation Professional since 2006 and was previously a NABCEP Certified Solar Heating Installer. He has a B.A. in business management from Columbia College Chicago and an MBA from the University of Nebraska-Lincoln. In his free time, he can be found working with his wife and daughter on their homestead in central Vermont, which features an off-grid straw-bale house.

Connect with Will on LinkedIn.

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