Achieving Commercial Operations in Large-Scale PV Power Systems: Page 4 of 6


High-quality documentation facilitates future transactions and forms the foundation for successful operations. With a standards-based performance test process, end-of-project documentation provides a baseline for benchmarking system performance against other assets in an owner’s portfolio, informs the operations and maintenance bid, and serves as a starting point for the plant evaluation documentation required when the asset is sold. Think of the standards-based performance test documentation as a factory acceptance test certificate for a fielded PV power plant. Without proper documentation, the asset is more difficult to maintain and sell for a high price because there is no proof that the site performs as expected.

At the precommissioning stage, it is useful to create a commissioning folder prepopulated with relevant forms and lists of required information. As the project approaches completion, this folder becomes a central repository for all of the documents and data that the project team will pass on to the owner and operations team. At project closeout, this folder should include the following:

  • Contracts and addenda related to the performance test
  • Test model, including descriptions of inputs, all assumptions and detailed output
  • Performance test technical standards
  • Performance test workbook with open-source evaluation methods and formulas
  • Combiner box as-builts identifying string counts, physical locations and names
  • Detailed map of inverters, combiners and current measurement channels
  • Datasheets and calibration certificates for all equipment
  • Plans and documents required for correct sensor installation
  • SCADA platform permissions and log-in information
  • Functional testing checklist and test results
  • Mechanical completion certification and substantial completion forms
  • Form for permission to operate, as well as other COD forms and requirements

Knowing what deliverables you need at project closeout is crucial to identifying and collecting the information and documentation for each successive step. Anyone who has gone through project closeout knows that proper documentation is conducive to a smooth and orderly process, whereas incomplete documentation results in a scrambling series of fire drills that waste time and resources.

Identifying string outages, for example, is a labor-intensive process unless you have accurately mapped the path of the combiner box wires to the inverter input channels. If you do not properly identify and map data points in the SCADA system, operations personnel cannot use the monitoring system to identify missing string inputs remotely. To obtain this information before energizing the plant, the project team needs to ensure that field personnel fill out forms documenting as-built field wiring conditions, and then pass the completed forms on to the SCADA vendor. If the team fails to do this work in advance, technicians can waste an entire day in the field as they will have to shut down each inverter in succession to document the wiring.

It is important to assign meaningful sensor names to aid with troubleshooting activities in both the near term and the future. Proper documentation also extends to naming conventions in the SCADA interface, as well as the labels inside equipment boxes. Since underperformance investigations typically start in the SCADA portal and lead to the field, we recommend assigning descriptors that identify the inverter, combiner box and string count. With a standard naming convention in place, performance analysts and service technicians can look at a label such as “02-04 [22]” and know immediately that there are 22 strings on combiner box 4 of inverter 2. This encoded information is useful for repairing problems or identifying any changes in field conditions after commissioning.


Proper planning, installation, commissioning and validation of the SCADA system and its meteorological sensors are essential to bringing a project to a successful close. Early in project development, the project team must discuss SCADA specifications and the associated design and installation details. Gathering this information cannot be an afterthought, as data acquisition is the single most decisive factor in the performance test outcome, pass or fail. To close the project out, the SCADA system needs to not only meet utility requirements, but also fulfill any contractual obligations related to performance testing. (See “SCADA Systems for Large-Scale PV Plants,” SolarPro, May/June 2017.)

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