What are the electrical safety requirements for photovoltaic systems during installation?

Photovoltaic systems have stringent electrical safety requirements during installation. The following are the key aspects:

Equipment and Component Requirements

• Photovoltaic modules shall be free of visible defects and shall exhibit excellent accessibility, scratch resistance, and continuity of equipotential bonding. Their pulse withstand voltage, insulation withstand voltage, leakage current under damp conditions, and terminal strength must all meet the requirements specified in the relevant standards. The rated voltage of the reverse-blocking diode installed in the module shall be at least twice the system voltage, and its rated current shall be at least 1.4 times the short-circuit current of the module.

• DC combiner box: It shall meet the requirements of GB/T 34933 and GB/T 34936. In particular, the DC switch shall be a DC switch specifically designed for photovoltaic systems and preferably equipped with arc detection and arc-extinguishing functions.

• Photovoltaic inverters shall meet the requirements of GB/T 37408 or NB/T 32004. Microinverters shall meet the requirements of NB/T 42142 and shall be equipped with power-limiting functionality, enabling them to automatically limit current and operate at the allowable AC output power under conditions of high capacity-to-inverter ratio.

Grounding and Lightning Protection Requirements

• Grounding: All metal frames and enclosures of electrical equipment must be reliably grounded, with a grounding resistance not exceeding 10 ohms, to prevent the risk of electric shock and lightning strikes.

• Lightning protection: The photovoltaic array must be equipped with a Class II surge protector to ensure effective lightning protection performance.

Overcurrent and Overvoltage Protection

• Overcurrent protection: The system must be equipped with appropriate overcurrent protection devices (such as fuses or circuit breakers) and must have isolation devices installed separately on both the DC side and the AC side, enabling rapid power disconnection in emergency situations.

• Overvoltage Protection: The inverter must be equipped with overvoltage protection (OVP) and overcurrent protection (OCP) functions. The DC input side shall be fitted with a reverse-blocking diode and a fuse, while the AC output side must have short-circuit current limiting capability.

Cable and Wiring Requirements

• Cable Selection: It is essential to use double-insulated cables that are resistant to ultraviolet radiation and high temperatures. The cross-sectional area of the cable must be calculated based on the current load and ambient temperature to prevent overheating and potential fire hazards.

• Wiring Specifications: The wiring for photovoltaic systems is divided into DC and AC sections. These two sections must be wired separately. The AC section must be connected to the power grid, with the connection point located at the user’s meter position, ultimately linking up with the user’s existing electrical system at home.

Installation and Operation Requirements

• Professional Qualifications: All personnel involved in photovoltaic installation and construction must possess the corresponding professional skills and qualifications—for example, electricians must hold a valid electrician’s license, and workers performing high-altitude operations must hold a high-altitude work permit.

• Safe Operation: The installation process must strictly follow the installation and user manual provided by the system supplier and should be carried out by qualified installation personnel. All wiring connections of the equipment shall be made using professional connectors, and the equipment boasts an IP65 protection rating. Additionally, all electrical devices are protected by air circuit breakers.

System Testing and Acceptance

• Electrical testing includes insulation resistance testing, grounding continuity testing, polarity testing, and open-circuit voltage testing, ensuring the system’s electrical safety performance.

• Acceptance: Organized by the project owner and the grid enterprise, this process focuses on grid-connected power performance, construction quality of the project, component certification, inverter certification and technical specifications, lightning protection and grounding, fire safety, and component fire-resistance certification.

These electrical safety requirements are crucial safeguards for ensuring the safe and reliable operation of photovoltaic systems and must be strictly adhered to.