How To Choose Spd Surge Protector For Photovoltaic System
Photovoltaic power generation is a renewable and clean energy source that is widely used in various countries and regions. Lightning strikes and surges are a major hazard to photovoltaic power generation systems. In order to protect the normal operation of photovoltaic systems, it is crucial to choose and install appropriate photovoltaic surge protectors.
What is a photovoltaic system?
A photovoltaic power generation system is a power generation system that uses the photovoltaic effect of semiconductor materials to convert solar radiation energy into electrical energy. The scope of a photovoltaic system extends from a photovoltaic array or a group of interconnected photovoltaic components to include related cables, protection devices, and inverters all the way to the distribution cabinet connection point or public grid connection point.
Why install SPD?
The equipment that may need protection in a photovoltaic system includes: (1) photovoltaic arrays; (2) inverters, including interfaces with low-voltage AC systems and interfaces with DC systems; (3) photovoltaic system wiring; (4) components installed between the inverter and the photovoltaic array; (5) equipment used to control and monitor the photovoltaic system.
These surges and overvoltages can reduce and destroy the performance of the photovoltaic system, and even cause equipment breakdown, burning, carbonization, etc. due to failures, and even cause fires in severe cases. Therefore, surge protectors should be installed in the photovoltaic system to effectively absorb and release these transient overvoltages and reduce them to a range that the equipment can withstand, thereby protecting the normal operation of the equipment and improving the reliability and safety of the photovoltaic system.
Selection of photovoltaic surges
The selection and installation of SPDs used to protect photovoltaic systems depends on many factors, such as: the characteristics of the low-voltage power system (such as overhead lines or underground cables) and the characteristics of the protected equipment; whether an external lightning device is installed to protect the photovoltaic system from direct lightning strikes.
1. Selection of DC side surge protector: (1) Photovoltaic inverter: It is a device that converts DC power (battery, storage bottle) into AC power. A pluggable modular photovoltaic-specific 2-level DC SPD needs to be installed on the DC side of the inverter; (2) DC distribution cabinet: It is not in the direct lightning protection zone, and a photovoltaic-specific 1-level DC SPD needs to be installed; (3) Combiner box: In order to reduce the wiring between the photovoltaic module and the inverter, facilitate maintenance, and improve reliability, a DC combiner box is generally added between the photovoltaic module and the inverter, and several photovoltaic series are connected in parallel to the combiner box; a pluggable modular photovoltaic-specific 2-level DC SPD needs to be installed.
2. Selection of surge protector on AC side: (1) Photovoltaic inverter: It is a device that converts DC power (battery, storage bottle) into AC power. On the AC side of the inverter, a pluggable modular photovoltaic dedicated 2-level AC SPD is usually installed; (2) Main distribution box: The AC power output by the inverter needs to be connected to the grid or directly supplied to the load. If it is close to the direct lightning area, a 1-level AC SPD needs to be installed at the main distribution box.
National standard regulations
According to the national standard GB/T 18802.32-2021 "Guidelines for the selection and use of surge protectors for photovoltaic systems", point 9 describes the selection of surge protector parameters: 1. For SPDs in Class II tests, the minimum nominal discharge current In for each protection mode is at least 15 kA, and the higher the value of 8/20us, the longer the SPD life; 2. According to SPDs in Class I tests, the Iimp of each mode of the DC side surge protector is at least 5 kA; the Iimp value of each required protection mode of the AC side surge protector shall not be less than 12.5 kA; 3. The maximum continuous working voltage UcPv/Uc of the surge protector should be greater than or equal to the system voltage of the DC/AC line; 4. The voltage protection level Up should be lower than the impulse withstand voltage rating Uw of the protected equipment, and Up should usually be kept no more than 0.8 times the equipment impulse withstand voltage rating Uw. There should be a 20% safety margin between the two. The lower the voltage protection level value, the better the protection performance.
