PD IEC TS 62804-2:2022 - Page 2

Photovoltaic (PV) modules. Test methods for the detection of potential-induced degradation. Thin-film | Status: Current

1 Scope This part of IEC 62804 defines apparatus and procedures to test and evaluate the durability of photovoltaic (PV) modules to power loss by the effects of high voltage stress in a damp heat environment, referred to as potential-induced degradation (PID). This document defines a test method that compares the coulomb transfer between the active cell circuit and ground through the module packaging under voltage stress during accelerated stress testing with the coulomb transfer during outdoor testing to determine an acceleration factor for the PID. It is designed for thin-film PV modules and modules containing moisture sensitive films protected by vapour barrier packaging, principally with one or two glass surfaces. This document tests for the degradation mechanisms involving mobile ions influencing the electric field over the semiconductor absorber layer or electronically interacting with the films such that module power is affected. This document does not specifically test for electrochemical corrosion or delamination associated with application of system voltage. This document does not contain pass or fail criteria and it is not intended for design qualification. The procedures contained herein, with testing in chamber in combination with in the field or testing in the field alone are intended for use when it is desired to quantify the acceleration provided by the applied stress levels over regular use conditions in the natural environment using coulombs transferred between the module and ground as the index for damage incurred by PID. The procedures for quantifying the acceleration are not recommended when coulombs transferred are not an indicator of damage by PID to the module. The procedures are not directly applicable when moisture ingress into the module laminate occurs affecting PID rate, and to the extent that there is power recovery when the factor of system voltage bias is removed after correctly applying the procedures herein, within the period of testing. The protocols given herein give results according to the chamber stress levels applied and the module grounding configuration used in the test. Because the stress method of testing in an environmental chamber employs a non-condensing humidity level to serve as a conductive pathway to electrical ground, it frequently applies relatively less stress toward the centre of the module face. Also, the method can evaluate the effectiveness of some construction methods to mitigate PID; for example, the use of rear rail mounts, edge clips, and insulating frames. The test, however, does not include all the factors existing in the natural environment that can affect the PID rate. The actual durability of modules to system voltage stress depends on the actual environmental conditions under which they are operated.