No fault found: Clearing the record on a direct-buried solar install
M&E Power is a full‑service electrical contractor headquartered in upstate New York. Over the past five years, solar has become the heart of the business. The M&E Power field leadership team includes Tom Zink, an electrical superintendent and IBEW 236 journeyman electrician, overseen from a quality standpoint by Mark Seager, QAQC manager and journeyman electrician. Their work includes utility‑scale solar projects ranging from 7 MW to 27 MW DC, covering territory from the Canadian border down to the Hudson Valley.
Their reputation is grounded in thorough, documented commissioning. Before every project is handed off, the team performs insulation resistance testing, voltage verification, and I‑V curve tracing using a lineup of professional‑grade test instruments, including the Fluke 393 Clamp Meter and the Fluke PVA‑1500HE PV Analyzer. On most jobs, everything checks out, documentation is filed, and the site goes live without incident.
But one project would put that documentation to the test in a way no one anticipated.
A persistent fault and a demanding manufacturer
The site had been fully commissioned. A single central inverter at the direct‑buried project was showing a ground fault warning and refused to fully engage. From M&E Power’s perspective, there was nothing wrong. Insulation resistance readings had been clean, voltage‑to‑ground measurements checked out, and commissioning documentation had been submitted.
The manufacturer’s position was firm: they would not dispatch a service technician until M&E Power could prove, again, that there were no ground faults in the cables or modules connected to that inverter. The client, understandably anxious to get their site generating revenue, passed the message along: please come back out, demonstrate the system is clean, and get them moving.
It was a difficult spot. M&E Power had already done the work correctly. They were being asked to re‑prove it — at their own expense if they couldn’t find a way to do it efficiently — and if any fault did turn up, the consequences would be significant. Excavating direct‑buried cable runs and replacing underground feeders on a utility‑scale site is not a small undertaking.
“Every minute it’s down, they have a problem, and there’s pressure to get it resolved quickly.”
— Mark Seager, QAQC Manager, M&E Power
The clock was running. The client needed the inverter online. And the old way of finding (or ruling out) a ground fault was not going to be fast enough.
The old approach: Slow, systematic, and stressful
Before the Fluke GFL‑1500 Ground Fault Locator entered the picture, troubleshooting a ground fault — or proving the absence of one — meant going manual. That meant de‑energizing equipment, isolating individual conductors, walking rows of modules, and working from combiner box to combiner box, breaking the system down to its simplest components.
“It could take half an hour to an hour, or it could take multiple days.”
— Mark Seager, QAQC Manager, M&E Power
On a large site with dozens of combiners and hundreds of strings, the process was exhaustive and time‑consuming even when the team executed it efficiently. And when the stakes involved underground cable replacement, the stress was not trivial.
For this job, that approach was off the table. There was simply too much system to test, too much at risk, and too little time to spend working string by string.
Deploying the GFL‑1500: A new kind of confidence
Mark had acquired the Fluke GFL‑1500 in the months following the original commissioning — partly because ground fault issues had come up before on other projects, and partly because the team wanted to be prepared when they did again. When the inverter manufacturer’s situation resurfaced, the timing turned out to be fortunate.
What made the GFL‑1500 particularly well‑suited to this challenge was its ability to test energized equipment. Rather than shutting everything down and isolating one conductor at a time, the team only had to de‑energize the central inverter, verify absence of voltage, and then connect the GFL‑1500 at the central inverter’s DC bus. From there, they were able to safely re‑energize the inverter and test every parallel‑connected conductor and solar module simultaneously — while the array remained live.
Tom walked through the process: they isolated individual DC feeders one by one through the DC disconnect just outside the inverter, testing each feeder through multiple layers of direct‑buried cable all the way out to the energized combiners. Each string, each cable run, each module — tested and confirmed clean. The results were captured with photos of the GFL‑1500’s display at each test point, documenting the estimated resistance and confirming no fault on every circuit.
The entire inverter was cleared in approximately three hours.
“We were able to hook it up at the central inverter and test every parallel‑connected conductor and solar module — all at once. I don’t know why anyone wouldn’t want to do that.”
— Tom Zink, Electrical Superintendent, M&E Power
Delivering the news to the manufacturer
M&E Power compiled their findings into a clear, concise report: a summary of the issue, a description of the testing methodology, photos of the GFL‑1500 connected at the inverter and at each combiner, and recommendations regarding the likely source of the problem inside the inverter itself. The report was delivered to the client and forwarded to the manufacturer.
After receiving the documentation, the client had no further questions. The manufacturer dispatched a technician. The root cause, as the team suspected, turned out to be a faulty insulation monitoring device inside the central inverter — not anything in the cables or modules M&E Power had installed.
The team’s workmanship was vindicated. The inverter came back online. And what could have become a protracted, expensive dispute was closed cleanly.
A novel use case: Proving a negative
What makes this story particularly interesting is that the GFL‑1500 was not used here the way most people think about ground fault locators. No fault was found because there was no fault to find. The value of the tool was not in locating a problem — it was in generating fast, credible, documented proof that no problem existed.
As Mark put it:
“It wasn’t necessarily locating the ground fault that it was good for. It was proving that it did not have one.”
— Mark Seager, QAQC Manager, M&E Power
That distinction matters. In O&M environments where contractors are accountable for their workmanship and must answer to both clients and equipment manufacturers, the ability to produce a fast, thorough, documented clean‑bill‑of‑health for a large solar array is genuinely valuable — and not something a megohmmeter or a multimeter can provide at scale.
“It also verified and vindicated us for doing our job correctly the first time.”
— Tom Zink, Electrical Superintendent, M&E Power
Looking ahead
For M&E Power, the GFL‑1500 has become a standard part of the kit that goes out the door on O&M calls. Mark described it simply:
“It’s kind of like an ace in the hole. It can get us out of a bind.”
— Mark Seager, QAQC Manager, M&E Power
On two subsequent O&M calls where clients reported intermittent ground fault error codes, Tom brought the GFL‑1500 along as a matter of course. In both cases, the fault had cleared by the time the team arrived — but having the instrument on hand meant they were ready to locate it if it had not.
The team also sees a natural fit for the tool in their construction workflow. As new projects move through the performance testing and commissioning phase, having a reliable way to quickly confirm the absence of ground faults adds another layer of confidence before handoff — and a ready defense if questions arise down the road.