Compared with the continuous rain and flood disasters in the Yangtze River Basin, South China has been in a state of high temperature for many days. In the scorching summer, the sky is dry and things are dry. For photovoltaic power generation systems that are exposed to the sun all year round, fire safety should be raised to the highest level at this time.
Fire is the biggest safety hazard of photovoltaic power plants. In addition to fires from external causes, the fire hazards of the photovoltaic system itself need to be paid more attention. According to statistics, about 70% of photovoltaic power plant fires are caused by equipment problems. Among them, the fires caused by combiner boxes, inverters, connectors, wires and cables, components, power distribution cabinets and transformers are the most common. Some power station fires are caused by equipment aging and not replaced in time, and some are related to quality problems of system components or engineering quality problems.
Equipment quality problems cause fires in photovoltaic power plants
Component problem: As the core equipment of photovoltaic power station, components are generally not fired when the fire rating is above B. At present, most of the fires are caused by poor quality of backplane and junction box materials and poor packaging technology. If the soldering area of ​​the module is too small or soldered, the insulation of the junction box is not enough or the assembly process is not good, and the photovoltaic backplane material fails, it will cause spontaneous combustion of the module.
In addition, the mixing of individual bad batteries, the false welding of electrode pads, the evolution of the battery from cracks to broken, the deterioration of individual battery characteristics, and the partial shadowing of the battery can easily cause hot spot effects. In order to avoid the hot spot effect, the usual practice is to connect a junction box with a bypass diode in parallel between the positive and negative electrodes of the component to reduce the hot spot effect. When a battery is blocked, the other batteries promote its reverse bias to become a large resistance. At this time, the diode in the junction box is activated to shield the battery piece with the problem, so as to avoid the blocked battery from being damaged by overheating.
Connector: It is another device that can easily cause fire. Inferior connectors are prone to arcing due to poor contact. The lighter ones will fuse the insurance and cables, and the heavy ones will burn components and equipment to cause a fire. In the case of current flow, if the resistance of the connector increases to increase the temperature rise and exceeds the temperature range that the plastic shell and metal parts can withstand, it is easy to cause a fire. Among them, the choice of insulating material directly determines the quality of the connector, especially the weather resistance, heat resistance, flame retardancy, and insulation of the material.
Cable: The choice of cable is also very important for fire prevention. Generally speaking, different connector models correspond to different cable outer diameters, the purpose of which is to ensure sealing performance. If the seal is not good, water and dust may enter when used outdoors, which will damage the insulation performance and cause a fire.
Inverter: There are many reasons why the inverter is prone to heat and fire, such as reduced performance of inductors, unstable capacitors, embrittlement and deterioration of plastic devices, shortened service life, reduced device insulation performance, reduced heat dissipation performance, and semiconductor device failure.
Combiner box: As a connection device for current convergence and shunting, the combiner box is also a device that is prone to heat and fire. The unreliable grounding of the combiner box and DC cabinet, the poor contact of the connector, and the confusion of the wiring are all likely to cause DC arcs or Fire caused by lightning strike.
How to effectively avoid fire in photovoltaic power plants?
Keep ventilation and pay attention to heat dissipation. Generally speaking, during the design of photovoltaic power stations, the brackets are usually raised to ensure that there is enough space around the front and rear of the modules to ensure air circulation and achieve the purpose of cooling. In addition, the metal frame around the components also has a certain heat dissipation effect, so daily protection and maintenance are required.
Proper shading treatment. This is mainly for inverters. Most photovoltaic inverters on the market are generally IP65 protection level, with certain wind, dust, and waterproof functions. However, in summer, the ambient temperature is high and the inverters are This kind of component device is prone to high temperature during operation, resulting in a decrease in power generation efficiency, and even affecting the life of components. Therefore, some inverters in photovoltaic systems are installed with sunshades to reduce the temperature of the equipment. In addition, the installation environment of the inverter should be well ventilated to ensure air convection and increase the power generation capacity of the power station.
What should I do if a photovoltaic power plant encounters a fire?
If a photovoltaic power station encounters a fire, it needs to be handled with care, and rescue work must be carried out on the basis of ensuring safety. The existence of high-voltage direct current in photovoltaic systems is the biggest factor hindering rescue work. Eliminating high-voltage direct current is an important way to solve the rescue problem of rooftop photovoltaic power stations. When fighting a fire, it is necessary to maintain a safe distance. If safety cannot be ensured, it is best to wait for the fire to diminish before carrying out the rescue. During this period, attention should be paid to control to avoid the fire spread.
Even if photovoltaic power plants have scientific and detailed fire-fighting specifications and equipped with correct fire-extinguishing equipment, they cannot prevent fire hazards caused by inferior products. We can only solve the problem from the source, strictly control the quality of products entering the market, and strictly implement relevant standards and acceptance Standardization can ensure the safety of power stations and ensure investors' income.
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