Sample Selection: The certification body will determine the number and method of sample selection. Generally, a certain number of representative samples from different production batches need to be selected for testing to ensure that the test results can reflect the overall quality of the products.
Testing Items: The testing items cover a wide range of aspects, including electrical safety, electromagnetic compatibility (EMC), performance - related tests, and anti - islanding protection (if applicable). For example, in electrical safety testing, items such as insulation resistance, withstand voltage, and grounding resistance are tested to ensure that the products do not pose electrical shock risks. In EMC testing, both electromagnetic interference (EMI) and electromagnetic susceptibility (EMS) of the cabinets are examined to ensure that they do not interfere with other electrical equipment and can also operate stably in an electromagnetic environment.
Quality Management System: The inspection team will review the manufacturer's quality management documents, such as quality control procedures, inspection standards, and record - keeping systems. They will check whether the manufacturer has established a complete quality management system and whether it is effectively implemented in the production process.
Production Process Control: The production process of photovoltaic grid - connected cabinets will be inspected. This includes checking the procurement and inspection of raw materials, the operation and calibration of production equipment, and the quality control of each production process. For example, the inspection team will verify whether the incoming raw materials, such as electrical components and enclosures, meet the specified quality requirements.
Product Sampling and Verification: During the factory inspection, samples may be randomly selected from the production line or the warehouse for on - site testing and verification. This is to ensure that the products produced in the factory are consistent with the samples that have passed the type testing.
Insulation and Withstand Voltage: Photovoltaic grid - connected cabinets must have sufficient insulation performance to prevent electric leakage. The insulation resistance between different electrical parts and between the electrical parts and the enclosure should meet the specified values. For example, the insulation resistance should be no less than a certain megohm under normal conditions. In addition, the cabinets need to withstand a certain voltage for a specified time without breakdown or flashover to ensure the safety of operators and the power grid.
Grounding: A reliable grounding system is essential. The grounding resistance of the cabinet should be within the allowable range to ensure that in case of a fault, the fault current can be safely conducted to the ground. The grounding terminal should have good conductivity and mechanical strength, and be clearly marked for easy identification and inspection.
Overcurrent and Overvoltage Protection: The cabinets should be equipped with effective overcurrent and overvoltage protection devices. These devices can automatically cut off the power supply when the current or voltage exceeds the rated values, protecting the internal components of the cabinet and preventing damage to the power grid.
Electromagnetic Interference (EMI): Photovoltaic grid - connected cabinets should not generate excessive electromagnetic interference to avoid affecting the normal operation of other electrical equipment in the vicinity. The EMI emissions, such as radiated emissions and conducted emissions, of the cabinets must be controlled within the limits specified by the relevant national standards.
Electromagnetic Susceptibility (EMS): The cabinets should also have good electromagnetic susceptibility, meaning they can operate stably in an electromagnetic environment without being affected by external electromagnetic interference. Tests such as electrostatic discharge immunity, radio - frequency electromagnetic field immunity, and electrical fast transient/burst immunity are carried out to verify the EMS performance of the cabinets.
Rated Voltage and Current: The rated voltage and current of the photovoltaic grid - connected cabinets should be clearly marked and meet the design requirements. They should be able to safely and stably transmit electrical energy within the rated range without overheating or other abnormal phenomena.
Power Transmission Efficiency: The power transmission efficiency of the cabinets is an important performance indicator. Higher efficiency means less energy loss during the power transmission process, which is beneficial to improving the overall efficiency of the photovoltaic power generation system. The power transmission efficiency should reach a certain level specified by the relevant standards.
Anti - Islanding Protection: In line with the requirements of grid connection, photovoltaic grid - connected cabinets need to have reliable anti - islanding protection functions. When an islanding event occurs, the anti - islanding protection device should be able to quickly detect and disconnect the grid - connected switch within the specified time to ensure the safety of the grid and maintenance personnel.