Switching from reactive to proactive O&M

10 February 2023


An ounce of prevention is worth a pound of cure, and maybe even more.

In utility-scale solar, projects generally budget $2.50 for preventive maintenance for every $1 spent on corrective maintenance, according to an operations and maintenance (O&M) pricing breakdown published by Wood Mackenzie in 2020.

For projects of any size, inefficient O&M practices can easily tip expenses out of balance, especially when O&M activities are generally limited to corrective maintenance.

The right tools will not only keep systems performing as they should but also manage the time and energy consumed by O&M.

Save time and energy

Switching from reactive to proactive O&M is easier said than done.

Some providers carry out tasks based on what is mandated by code. For example, the 2020 edition of the National Electrical Code discusses methods for bonding the non-current-carrying metal parts of solar equipment. See Section 250.92(B) Method of Bonding at the Service and Section 250.97 Bonding for Over 250 Volts for details.

But the NEC does not set requirements for testing continuity. This leaves the test methods up to the provider’s discretion. If you’re testing for continuity between two pieces of metal that are one meter apart, it’s nearly impossible to get a negative result. If the parts are separated by 100 meters, that’s another story.


For proactive O&M, providers have to go beyond the activities that are required by code. You also must be ready to collect baseline data early in the system’s operational lifetime.

When measuring insulation resistance, the data that you collect on a site visit today is most useful if you can compare it to measurements obtained in previous visits going back to the start of commercial operations. The trendlines that you establish over many years of preventive maintenance will help you decide whether it’s time to take corrective action and, if so, the best course of action to take.

Get more proactive in 5 steps

Once you are out in the field to locate and resolve a ground fault, the time for proactive O&M has passed. But many of the tasks that you perform during corrective maintenance should also be completed before a service disruption occurs.

Here are five ways you can adapt routine maintenance activities to emphasize prevention.

1. Measure voltage and current

Standardize around one digital multimeter that can measure up to 2,000 volts and one clamp meter that can read up to 1,500 amps. Test tools have improved in recent years. Keep your kit up to date.

2. Chart trend lines on tested conductors

An insulation resistance tester can be used to identify faults located in cables. Just as important, it can be used to create trend lines on the tested conductors. Use it for both activities.

3. Document and interpret test results

Documentation can be the most arduous part of an O&M provider’s job. Tools with advanced features such as Bluetooth connection to smart devices and on-board data storage help users move quickly through testing while collecting accurate data.


4. Verify continuity of metal components

The length of your test leads affects not just the quality of the results you can obtain when measuring for continuity in a photovoltaic (PV) system’s non-current-carrying metal parts. It also affects how much time you spend collecting data. Once again, instead of sacrificing speed for accuracy or vice versa, choose both.

5. Verify grounding system

A lightning strike or high-voltage power surge can cause extensive equipment damage. A high-resolution earth tester can raise the standard for low-voltage systems, easily and accurately verifying a good connection to ground.

Tools of the trade

The wind industry has a high standard for safety and component risk mitigation to protect against injury and death, as noted in IEC 61400. Wind power operators test for continuity from the tip of the blade to the grounding system. Electrical substation operators consider low-resistance earth systems essential for the maintenance of equipment safety. Advanced test tools can help transfer best practices from the wind power and utility industries to the solar industry.

O&M providers are understandably most comfortable and confident using familiar equipment and following familiar processes. But solar O&M is rife with opportunities to improve speed and accuracy and prevent downtime due to ground faults and equipment damage.

Keep an eye on the Megger blog for an upcoming post on using Megger tools to carry out essential O&M activities.