ABSTRACT
The Field Wet Resistance Test (FWRT) is a procedure used to evaluate the integrity of a PV array's insulation. A field version of the Wet Insulation Integrity test in IEEE 1262 and IEC 60146. this test evaluates wiring, connectors, and junction boxes in addition to module encapsulation. A decade of experience at PVUSA shows that arrays nearly always pass easily or fail miserably. The test deftly locates nicked wire insulation, loose junction box covers, screw driver-penetrated module backsheets, inadequate connector seals, hairline cracks in module junction boxes, and other potentially unsafe and unreliable conditions. These mechanical problems are typically indicated as a short or near short to ground in the presence of an aqueous surfactant. Even without these problems, there are often large variations— factors of 2 to 10— in readings throughout the array. In this paper, we investigate a number of variables that affect the measured wet resistance of a PV array. Sorting through these variables will lead to more accurate measurement and diagnosis of impending failures. Results indicate glass temperature and settling time have a much greater influence than previously anticipated. Conversely, surfactant concentration and array voltage have very little effect.
