The standard “IEC TS 62804-1 Photovoltaic (PV) modules - Test methods for detecting potential-induced degradation - Part 1: Crystalline silicon”, published by the International Electrotechnical Commission (IEC), describes procedures for testing and evaluating the durability of crystalline silicon photovoltaic (PV) modules against the effects of short-term high-voltage stress, including potential-induced degradation . This standard includes two test methods that do not inherently produce equivalent results. These are presented as screening tests. Neither test includes all factors found in the natural environment that could affect the rate of potential-induced degradation.
The methods describe how to achieve a constant stress level. These tests are designed for crystalline silicon PV modules with one or two glass surfaces, silicon cells with passivating dielectric layers, degradation mechanisms involving mobile ions affecting the electric field on the silicon semiconductor, or those that interact electronically with the silicon semiconductor itself.
This standard is not designed to evaluate modules with thin film technologies, tandem or heterostructure devices. This standard describes methods to measure the robustness of a module design against degradation due to system voltage effects that occur over relatively short periods of time. These tests are not intended to examine specific combined effects that may occur in modules over longer periods of time, such as encapsulation failure, which can lead to rapid moisture ingress and electrochemical corrosion.
This standard does not include illumination of the module, which could affect the rate of failure. The test methods are designed to measure the susceptibility to potential-induced failure and provide results specific to the tests and module grounding configuration.
Because the voltage testing method in an environmental chamber uses a non-condensing moisture level to act as a conductive path to electrical ground, it often applies less voltage toward the center of the module face, with the result that the potential-induced degradation effect is concentrated toward the module edges.
The voltage method, which places surfaces in contact with a grounded conductive electrode, evaluates cell sensitivity and some effects of component packaging materials such as glass and encapsulation resistance. However, it does not distinguish the effects of some construction methods to mitigate potential-induced degradation, such as the use of back rail mountings, edge clips, and insulating frames. The actual resistance of modules to system voltage stress depends on the environmental conditions in which they are operated. These tests aim to evaluate the susceptibility of the PV module to potential-induced degradation independent of the actual stresses in different climates and systems.
Test specimens shall be representative of the material being tested. When a product is intended for use in one position only, three specimens shall be tested by the same method with the steam flow in the specified direction. When the surfaces of a product are indistinguishable, three specimens shall be tested by the same method. When the surfaces of a product are different and the location of the steam source is independent of the installation, six specimens shall be tested by the same method, three with the steam flow in each direction, and reported as such. A blank specimen is required for both orientations.
Materials of homogeneous composition and physical structure should be tested at any thickness to determine water vapor permeability. When determining permeability, the sample should be at least 12,5 mm thick.
A sheet made of a single material whose physical structure varies from layer to layer (e.g. natural shell foam plastic or rubber) should be tested at its usage thickness.
If a material has a pitted or textured surface, the overall tested thickness, if less than the service thickness, shall be at least five times the sum of the maximum pit depths on each face.
When testing joints sealed with pressure-sensitive adhesives used in insulation vapor retarder systems, samples are prepared in accordance with ASTM C1809.
All tests require an additional blank sample to be tested, as do all others, except that no desiccant or water is added to the container. Failure to use this blank sample to determine the modified container weights may significantly increase the time required to complete the test. The time to reach equilibrium for water vapor transmission increases with the square of the thickness. Some thick, particularly hygroscopic materials may take up to 60 days to reach equilibrium conditions.
The blank sample is used to eliminate the effects of barometric pressure changes and eliminates the need for buoyancy corrections, moisture changes of hygroscopic materials, and mass changes of uncured samples. This provides simpler and more accurate calculations and reduces the time to determine steady-state mass change.
The blank sample becomes the fourth sample in a standard three-plate test set.
Our organization, which has been trying to support businesses from every sector with its testing, measurement, analysis and evaluation studies carried out in a wide range for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services in accordance with the “IEC TS 62804-1 Photovoltaic (PV) modules - Test methods for the detection of potential-induced deterioration - Part 1: Crystalline silicon” standard are also provided to businesses.
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