PV Systems Reliability Final Technical Report.

Abstract

Project Objective:The continued exponential growth of photovoltaic technologies paves a path to a solar-powered world, but requires continued progress toward low-cost, high-reliability, high-performance photovoltaic (PV) systems. High reliability is an essential element in achieving low-cost solar electricity by reducing operation and maintenance (O&M) costs and extending system lifetime and availability, but these attributes are difficult to verify at the time of installation. Utilities, financiers, homeowners, and planners are demanding this information in order to evaluate their financial risk as a prerequisite to large investments. Reliability research and development (R&D) is needed to build market confidence by improving product reliability and by improving predictions of system availability, O&M cost, and lifetime. This project is focused on understanding, predicting, and improving the reliability of PV systems. The two areas being pursued include PV arc-fault and ground fault issues, and inverter reliability. PV arc-faults and ground faults have caused hundreds of fires in the U.S. and around the world [1]. In cases of faults on rooftop systems, the resulting fire can burn down the building and put the occupants' lives at risk. In 2011 arc-fault circuit interrupter (AFCI) safety devices were required by the National Electrical Code® [2] on rooftop systems. AFCI products are being listed to the UL 1699B Outline of Investigation, but Standards Technical Panel (STP) experts strongly disagree on which UL requirements should be revised, retained, or modified when converting the UL Outline into a Standard. The STP does agree that the current Outline requires modification because UL-listed AFCIs are experiencing unwanted tripping in the field. Thus, in order to reach a consensus on these topics and convert the Outline of Investigation into a UL Standard, Sandia is performing extensive research into consistent arc-fault generation and nuisance tripping testing. Similarly, the International Electrotechnical Commission (IEC) Technical Committee 82 (TC 82) is creating an arc-fault certification standard and Sandia is collaborating closely with the international group to make the testing procedure realistic for PV installations, establish methods to avoid unwanted tripping, and ensures repeatability of the tests. When an arc-fault or ground fault detector trips in a PV system, no information is provided to the operator about the location of the fault. Determining the location is especially challenging in large PV systems consisting of acres of PV modules. If the problem is not identified quickly, the system operator will continue to lose money and could potentially assume the trip was the result of a nuisance trip and mistakenly turn the system back on. Developing a technology to locate the arc or ground faults will give PV system operators a means to resume operations quickly and minimize the risk that system will restart occurs without repairing the problem. The challenge of locating PV arc and ground faults has be...

Reliability Analysis of Photovoltaic Systems for Specific Applications

“…The results obtained by the authors were partially validated by other authors research studies, regarding the availability and degradation of analyzed systems [34,35].…”