For continuous operation of the station it is necessary to diagnose and check the serviceability of the equipment on time. It consists of the following stages: visual inspection of photovoltaic modules, inspection by thermal imager, measurement of volt-ampere characteristics and inspection of inverters. It is carried out by technical engineers of the company that installs and maintains the solar power plant. 

Stages of visual diagnostics of solar modules of the station

Visual inspection consists of diagnostics of solar modules – front and back side. What problems can be identified during the inspection? 

  • Label problems on solar panels. It must be intact, contain the technical characteristics of the module, information about the manufacturer and serial number.
  • Detachment of the back lining of the module (yellowing / discoloration). The substrate protects the internal elements from environmental influences. Bundling indicates the accumulation of moisture in the solar module, which can reduce productivity and affect the long-term reliability of the station.
  •  Problems with the distributing  box. The electrical housing on the back panel of the module, where the external wires are connected to the internal conductive busbars, may have cracks or no sealant
  • Missing or too short cables, breaking the integrity of the insulation.
  • The windshield, which provides the structure of the module and protects the solar cells, should not be cracked or even scratched.
  • Stratification of EVA film, which protects the solar module from moisture and ultraviolet radiation. 
  • Solar cells, materials that generate electricity and convert sunlight into direct current, must not be counterfeited or masked by other similar materials, have a significant difference in the color of cells of the same type and batch. 
  • The live parts of the module element may not be connected to the main busbars or may not have the same pattern on all solar cells

Technical engineers distribute the failure of solar modules according to the severity of the detected defects. Where the first level indicates defects with poor quality without a direct impact on productivity, and the fifth indicates an important problem that greatly affects the quality of work. 

Diagnosis of solar modules by thermal imager

The thermal imager shows the main thermal deviations of the solar power plant – the so-called “hot spots”: 

• Damage to the windshield in the event of severe hail or other mechanical stress.

 • Cells overheated due to manufacturing failures. For example, there was an inaccuracy in cell sorting, local short circuits in the solar cell, or insufficient electrical contact. 

• Cell overheating due to external shading by plants, metal rod, satellite dish, chimney, power line supports or even due to incorrectly placed adjacent parts of the modules. 

• Heated bypass diodes inside the junction box of the PV module

Thermal imaging of solar modules allows you to identify potential problems with the panels before the failure of the entire station and make timely repairs. 

Measurement of volt-ampere characteristics (I–V curve) 

The control measurement of the I – V curve indicates performance factors and possible problems of the module, rows, arrays. To measure it, engineers install the insolation sensor at the same angle as the solar modules, and for each square meter of the module, the beam power should be 1000W.

 After analyzing the current-voltage characteristics of the station, experts can accurately determine the problem using a special algorithm. For example, the reduction of output power from a number of solar modules to 40% was influenced by partial shading of the array, not pollution. If the measured and predicted data match, the productivity factor is 100%.

Checking inverters for a solar power plant

The energy audit of a solar power plant includes checking the inverters. It consists of three stages:

 • Software updates. 

• Inverter maintenance. 

• Replacement of components or units of equipment.

Software updates must be performed to correct errors and improve the stability of solar panels. Sometimes changes or additional settings are made to comply with network standards.

 The maintenance of inverters includes checking its operation without alarms. Technical engineers pay attention to the integrity of cables, connectors and cable entries outside the inverter. Checking the tightening of the screw terminals, attaching the front cover to the wiring box.

 Diagnosis of inverters at the top, bottom and between the ribs for obstacles (animals, insects, leaves, which may reduce the heat transfer capacity of heat dissipation) is also performed. Engineers then check that all labels and safety symbols are visible. If it is necessary to repair the solar inverter, experts replace some components depending on the model of the inverter and the manufacturer’s policy. This may be the replacement of printed circuit boards, a piece of equipment or individual units (power unit, switching unit). 

You can learn more about the capabilities of the Unisolar service department at the link –

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