Standardizing PV System Documentation and Verification
Inside this Article
International concern regarding the safety and quality of PV system installations is growing. Incorrectly installed or commissioned systems can create a fire hazard or even increase the risk of electrocution.
Consider the well-documented “thermal event” that occurred in Bakersfield, California, on April 5, 2009 (see “The Bakersfield Fire,” February/ March 2011, SolarPro magazine). It is generally accepted that an undetected fault-to-ground was present in a grounded current-carrying sourcecircuit conductor at this site, and that this first fault set the stage for the eventual fire. A subsequent analysis of utility-owned and -operated rooftop PV systems in North Carolina revealed the presence of undetected ground faults in approximately 10% of the systems surveyed.
Proper commissioning procedures are among the best defences against fire or electrocution hazards. While guidelines and best practices for PV system commissioning in North America are patchwork at best, in 2009 the International Electrochemical Commission (IEC) published an international standard, IEC 62446, that defines minimum requirements for documenting, commissioning and inspecting grid-connected PV systems.
In this article I provide an overview of IEC 62446, which can be purchased in its entirety from the IEC website (iec.ch) for approximately $150. In addition to the general content outlined here, the standard includes informative appendices with model certificates, reports and procedures.
While compliance with IEC 62446 is not mandatory in North America at this time, the standard clearly provides a set of internationally recognized best practices for system integrators and O&M providers. Since these entities are already performing many of the tasks described in the standard, the effort and cost to harmonize internal practices with those outlined will be relatively small. Anyone engaged in the preparation of documents and standards for projects going out to bid will likely find the requirements outlined in IEC 62446 useful and relevant to their work as well.
This international standard was published in March 2009. It is formally entitled Grid-Connected Photovoltaic Systems—Minimum Requirements for System Documentation, Commissioning Tests and Inspection. The emphasis on documentation is interesting to note. In effect, system documentation is the evidence used to demonstrate that appropriate precautions and tests have been undertaken prior to handing over a PV system to the property owner. The standard is organized into two parts: system documentation requirements and system verification requirements, which include inspection and testing.
System documentation requirements are laid out in Clause 4, which describes the minimum documentation that should be provided for the benefit of the customer, inspector or maintenance technician following the installation of a grid-connected PV system. These requirements are organized into six categories: system data, wiring diagram, datasheets, mechanical design information, O&M information, and test results and commissioning data.
System data. Minimum system data requirements outlined in IEC 62446 include basic nameplate information and details that you would expect to find on the cover page of a PV plan set or a system commissioning package. Nameplate data requirements include rated system power and the manufacturers, models and quantities of PV modules and inverters. Cover page data requirements include contact information for the customer, system designer and system installer, plus relevant project dates.
Wiring diagram. According to IEC 62446, system documentation for a gridconnected PV system shall include at minimum a single-line wiring diagram. A list of subsections outlines the specific information that needs to be included in the notes or tables associated with the wiring diagram.
Annotations to the single-line diagram must include general information about the quantity and type of modules, as well as specific details about the source-circuit and subarray makeup. IEC 62446 also requires information about the location and type of balance of system components. Details need to be provided regarding conductor sizes and overcurrent protection device ratings.
In addition to equipment grounding details, in particular module frame grounding, any connection to an existing lightning protection system needs to be identified, as do the locations, types and ratings of ac or dc surge protection devices. IEC 62446 also details minimum information requirements regarding the existing ac electrical system.