The rapid growth of photovoltaic plants in Brazil has brought a new challenge to the sector: ensuring that the assets maintain performance, safety, and reliability throughout their entire lifespan.
In many projects, there is intense concern during the implementation and initial commissioning phase, but a significant reduction in the level of technical support after the start of operations.
In practice, this lack of periodic inspections and specialized testing can result in silent energy losses, premature equipment degradation, increased fire risk, and reduced plant operational availability.
The main international O&M standards for photovoltaic systems, as well as relevant technical documents on the subject, such as IEC 62446-1, IEC 62446-2, NREL (National Renewable Energy Laboratory) guides, SolarPower Europe and IEA-PVPS, highlight that periodic inspection, preventive maintenance and electrical testing activities are fundamental to preserving the performance and safety of power plants over the years.
IEC 62446 itself establishes that tests performed during commissioning can also be used in periodic reinspections and plant maintenance activities, especially in systems subject to aging, severe weather, or aggressive environments.
Performance loss is not always noticeable in the supervisory system.
One of the biggest problems in photovoltaic plants is that many faults develop slowly and remain "invisible" to conventional supervisory systems. Often, the plant continues to generate energy and does not show critical alarms, but is already operating with significant losses.
Connections with high resistance, hotspot modules, potential-induced degradation (PID), string mismatch, moisture infiltration, bypass diode failures, excessive dirt, faulty connectors, and grounding problems are classic examples of faults that can remain unidentified for months or years.
In medium and large-scale power plants, such as mini-generation and centralized plants, small losses distributed across hundreds or thousands of strings can represent extremely significant financial impacts over time. Furthermore, certain defects significantly increase the risk of catastrophic failures, such as arc flash, connector meltdown, and fires.
Therefore, the modern concept of O&M in solar power plants has moved beyond simply corrective maintenance and has come to incorporate a predictive and diagnostic approach, based on periodic inspections and specialized testing.
Thermography: one of the most important tests at the plant.
Infrared thermography is currently one of the most important tools in the preventive maintenance of photovoltaic power plants.
Its main advantage is that it allows the identification of thermal anomalies without the need to shut down the plant. Thermographic inspections can be carried out with drones or handheld cameras, depending on the type of analysis desired.
Among the main problems identified by thermography, the following stand out: hotspots in modules; damaged cells; bypass diode failures; overheated connectors; defective fuses; poor contact in terminals; unbalanced strings; overheating in inverters, main distribution boards, and transformers.
IEC 62446-3 establishes specific guidelines for thermographic inspections of photovoltaic systems, including execution criteria, environmental conditions, and classification of thermal anomalies.
In addition to the direct impact on power generation, several studies indicate that thermal anomalies can evolve into serious safety failures if they are not addressed preventively.
Several technical guides and important documents on this subject recommend periodic thermographic inspections as an essential part of the preventive maintenance strategy for photovoltaic plants.
In market practice, many specialized companies perform annual thermographic inspections at utility-scale power plants, especially before periods of higher irradiance.
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Figure 1: Thermography identifies a short circuit between seven modules of a string.
Curve IV: the “clinical examination” of photovoltaic strings
Among the most relevant electrical tests for evaluating plant health, the IR curve test stands out. This test allows for the electrical evaluation of the behavior of photovoltaic strings, comparing the results measured in the field with the manufacturer's expected values corrected for irradiance and temperature.
Analysis of the IV curve makes it possible to identify: low-power strings; mismatch between modules; premature degradation; connection problems; shadowing; excessive dirt; module failures; changes in the curve's shape factor (Fill Factor).
The IV curve test can be classified as one of the important methodologies for verifying and maintaining photovoltaic systems. Furthermore, manufacturers and international technical references recommend that the curves be compared with historical measurements from the plant itself, allowing for the monitoring of degradation trends over time.
In many practical situations, the IV curve can identify problems that are not evident in either thermography or the plant's supervisory system. Figure 2 shows a subtle difference in the IV curve of an inverter string that is often imperceptible in thermographic tests and system monitoring.
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Figure 2: String with a slight generation deviation compared to the others.
Electrical tests and complementary inspections
In addition to thermography and IR curve testing, O&M programs often include other important tests, such as:
Detailed visual inspection
Detailed visual inspection allows for the identification of: module delamination; cracks; corrosion; water infiltration; damaged cables; oxidized structures; inadequate connectors; mechanical problems in trackers.
Despite its simplicity, visual inspection remains one of the most important activities in preventive maintenance.
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Figure 3: Cut corrugated conduit, allowing water infiltration and future problems of poor insulation in the DC strings.
Insulation resistance measurement
Essential for identifying electrical degradation, moisture infiltration, and insulation faults in DC circuits. Insulation problems are frequently associated with intermittent faults, protection tripping, and arc flash hazards.
Modern photovoltaic inverters typically have built-in insulation monitoring functions capable of detecting ground faults or earth faults and critical insulation degradations during operation.
However, these embedded systems primarily act as operational protection and safety mechanisms, and do not replace periodic insulation resistance tests performed in the field with appropriate instruments.
This is because incipient faults, intermittent degradation, localized moisture, microcracks in cables, and problems that arise only under certain environmental conditions may not be accurately detected by continuous inverter monitoring.
Therefore, dedicated insulation tests remain essential for a more thorough assessment of the electrical integrity of the photovoltaic system and for the early identification of defects that can lead to recurring outages, generation losses, and even arc flash or fire events.
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Figure 4: Insulation resistance test on AC cables connecting the inverters to the main distribution board.
Testing of medium voltage equipment
In larger power plants, periodic inspections and preventive maintenance activities are also recommended for: transformers; switchgear; circuit breakers; current transformers (CTs) and potential transformers (PTs); protection relays; supervisory and communication systems.
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Figure 6: Testing the protection functions of a relay using a test case.
What frequency should I adopt?
The frequency depends on the size of the plant, the criticality of the asset, environmental conditions, and contractual O&M requirements. However, Table 01 presents examples of recommended frequencies based on good O&M practices in photovoltaic plants.
Table 1: Examples of recommended periodicities in good O&M practices in photovoltaic plants.
| Activity | Usual frequency in O&M |
| Remote monitoring | Continuo |
| Visual inspection | Monthly, quarterly, or as needed. |
| Thermography | Annual or semi-annual |
| Curve IV | Annual, biennial, or performance-based. |
| Insulation tests | Annual |
| Grounding check | Annual |
| Module cleaning | Based on analysis of local dirt and environmental conditions. |
| Tracker inspection | Semiannual or annual |
Documents from NREL, SolarPower Europe, and IEC reinforce that well-structured preventative programs reduce downtime, increase reliability, and improve the profitability of the project in the long term.
Modern O&M is based on data and diagnostics.
The operation and maintenance of photovoltaic plants has evolved significantly in recent years. Today, more mature companies in the sector no longer rely solely on supervisory alarms or corrective maintenance after severe failures.
The global trend is towards the combined use of: continuous monitoring; periodic inspections; specialized testing; predictive diagnostics; performance history; and analytical intelligence.
This approach allows for the detection of faults at an early stage, reducing energy losses and increasing the lifespan of assets. In a scenario of increasingly tight margins and growing professionalization of the solar sector, maintenance based solely on fault correction is no longer sufficient.
The operational reliability of the plant depends directly on the quality of the technical inspections and the depth of the tests performed throughout the plant's lifespan.
The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.
Comments (1)
Comments are moderated before publication.Comments should be respectful and contribute to a healthy debate. Offensive comments may be removed. The opinions expressed here are those of the authors and do not necessarily reflect the views of the author. Canal Solar.
Congratulations on the article, Geraldo. Individual monitoring of photovoltaic modules using a power optimizer would be another relevant technique in predictive maintenance.