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Excerpt of a presentation from the EAI Solar PV Developer – EPC Meet, Chennai, Jan 22, 2013

Inspection, Testing and Certification of PV Power Plants – B S Arun Kumar, Senior Manager, TÜV Rheinland

The Developer-EPC meet featured a presentation on Inspection, Testing and Certification of PV Power Plants by Mr. B S Arun Kumar of TÜV Rheinland (India). He spoke about the need for testing and verification and provided numerous examples of preventable failures that occurred in solar plants.

Mr. Arun Kumar began his address to the audience by posing a question on the outcome of Phase 1 JNNSM, by pointing to the many disagreements on plant performance between Independent Power Producers (IPPs) and the EPCs who implemented their projects and the need to bridge this gap. He shared a few details of some of the tests conducted by his company before discussing two issues specific to panels

  • Potentially Induced Degradation (PID) – It is an issue that has newly emerged and is predominant in Thin Film modules
    •  Causes loss of power (up to 20%) due to current leaking at higher voltages
    • Temperature and humidity are the two main causes, with plants in Gujarat and Rajasthan (particularly the latter) experiencing module failure to this
    •  The temperature difference between day and night (up to 50°C in the morning in Rajasthan followed by a plunge at night) causes moisture condensation during the night on the panels which causes problems when the panels begin generating power in the morning
    • Losses can be minimised by buying panels that are tested and certified as anti-PID
    • Transparent Conductive Oxide (TCO) Corrosion –This is again an issue that is increasingly seen in Thin Film modules
      • Causes failure of the module due to delamination of the glass covering caused by the reaction of sodium in the glass with the TCO layer in the presence of moisture
      • A-Si and CdTe modules with substrate technology are affected the most

He continued by speaking of mitigating the risks to the power plant as a whole through adoption of IEC/EVS EN62446 by improving the safety and quality of the plant through testing and verification at the site

  • Testing – A lot of testing equipment needs to be used to identify issues with solar plants as they work silently and give no easily noticeable indication of malfunction
    • IV Tracer – Indicates health of the module through IV curve, insulation resistance, and current and voltage measurements of the string
    • Infrared camera – This is very important as it identifies
      • Hot spots – Caused by shadows falling on the panels. When a cell comes under a shadow it turns from a conductor into a resistor which causes heating leading to the cell burning out at which point the panel has to be replaced. Shadows are caused by nearby mountains, buildings, trees, inverter rooms, and in one case by the onsite lightning arrester
      • Junction box burn out – Caused by loose connections and components unsuited to such voltage and current requirements

Mr. Arun Kumar shared photos and examples of different kinds of failure at solar plants

  • Ethylene-Vinyl Acetate (EVA) discolouration – EPA sheets that are not used within 8 days of being unpacked develop discolouration which affects power output
  • Charanka park – During the rainy season it is flooded two months in the year
  • Rajasthan has clay soil, and on one site the foundation for the panels sunk into the ground after the rains as clay becomes brittle once dry
  • The bund of a lake was broken at a village in Rajasthan, flooding the nearby solar plant

He concluded his presentation with visuals of well designed and implemented plants.