Electricity, commonly known as "electric tiger", is an invisible and intangible thing that plays a great role in modern people's life, but it is also very dangerous. Photovoltaic power generation projects, whether distributed small power stations or centralized large ground power stations, have certain dangers. Photovoltaic safety accidents are not uncommon. For various reasons, few reports have been reported before. After the photovoltaic power station on Apple's factory caught fire, there was a great uproar inside and outside the industry. Apple's share price also fell, with heavy losses
1. Fire is the most economic loss accident of photovoltaic power station.
Once a fire occurs in the photovoltaic power station, water cannot be used directly to extinguish the fire. If it is installed on the roof of the plant or residential buildings, it is also easy to endanger personal safety.
There are many reasons for fire accidents in photovoltaic power plants, mainly including the following aspects: 1) aging or failure of equipment and cables, resulting in short circuit; 2) Improper selection and installation of fuses and circuit breakers, resulting in DC arcing; 3) The system design is defective, the current carrying capacity of cable or switch is too small, and the local temperature is too high; 4) Improper construction, loose screws of electrical equipment, insecure crimping of cable joints, and excessive contact resistance at selected joints; Or if the screw is too tight and the cable connector is deformed during crimping, the contact resistance at the connector may be too large.
2. Typhoon, lightning, snow, sand and dust and other natural disasters.
At the beginning of the design of the photovoltaic power station, it is necessary to consider the local climate conditions and the impact of natural disasters on the photovoltaic power station, and reasonably design and select the type.
For example, a photovoltaic power station in Wenchang, Hainan, was hit by a typhoon, and almost all of its components were damaged. The inverter manufacturer was a solar power centralized inverter, which was installed in two steel structure inverter rooms. The inverter was timely disconnected, so it was not damaged.
3. Explosion accident
Although there are few explosion accidents in the photovoltaic power station, they have a great impact on the safety of operation and maintenance personnel. The explosion mainly comes from IGBT and capacitor inside the inverter. The explosion of a capacitor is very powerful and can break through a 2mm thick steel plate. How to prevent accidents in photovoltaic power station before they happen. A cuddled tree is born in a tiny hair. Behind any serious accident, there must be 29 minor accidents, 300 near misses and 1000 potential accidents. This is the inventor of the airplane turbine, German Pabbs ˙ The safety rule proposed by Hain is called "Hain rule" for short.
In fact, photovoltaic power station is not a monster. Like household power system, there are certain risks, but the accident rate can be minimized through various protective measures. For the safety of photovoltaic power station, consideration should be taken from the beginning of design to avoid potential accidents from the root. Due to the complex causes of PV power plant accidents, it is impossible to describe them one by one. Here are just a few typical examples:
1. Use appropriate fuses.
The characteristic of electrical fire is that the burning speed is very fast, which will damage the equipment of a system in a moment. In case of electrical fire, first of all, find a way to quickly cut off the power circuit within the fire range. Fuse, commonly known as fuse, can quickly cut off the circuit in case of short circuit to avoid greater loss, so it is widely used in the power industry. However, if the fuse is not properly selected, it will cause DC arcing and other hazards to the system.
(1) The fuse should select the appropriate rated current. If the current is too small, it is easy to misjudge. If the current is too large, it will not play a protective role.
(2) The main causes of short circuit, arc and spark short circuit are the insulation damage of current carrying parts, such as insulation aging, voltage withstand and mechanical strength reduction, insulation breakdown caused by overvoltage, incorrect operation or power supply to the fault line, damage to the metal insulation layer of the line caused by impact of foreign matters caused by strong wind in severe weather, and damage by rats or other small animals. In fact, poor contact is caused by excessive contact resistance, local overheating, arc and electric spark, and potential ignition source.
(3) The fuse inside the combiner box shall be equipped with a special DC ceramic structure fuse core and a corresponding fireproof and arc proof base, and the exposed fuse core and PCB board design shall not be used.
2. Lightning protection design of photovoltaic system.
For solar photovoltaic power generation system, direct lightning, lightning induction and lightning wave intrusion shall be prevented. Direct lightning protection includes protection of solar cell array and photovoltaic power plant. Lightning rod and lightning strip are mainly used for lightning protection equipment. The main way of lightning induction and lightning wave invasion is the incoming line from overhead conductor and photovoltaic array to the machine room. Multilevel protection measures can be taken to protect the solar photovoltaic power generation system. Lightning arrester is installed in combiner box, inverter and AC distribution cabinet.
The grounding of photovoltaic system is also very critical. On the one hand, it is the need for lightning protection of the system; on the other hand, it is the need to eliminate the static electricity of equipment. The construction should be carried out in strict accordance with the standards. Many distributed photovoltaic projects do not pay much attention to it. If the ground wire is not installed properly, no good lightning protector is useful.
3. The omen of an accident in the photovoltaic power station.
Compared with hazardous chemical warehouse and chemical plant, the safety factor of photovoltaic power station is very high. As long as climate factors are fully considered in the early system scheme design, high-quality equipment is selected and construction quality is emphasized, the accident rate can be minimized. Any major accident must have many omens and minor accidents in advance. During the operation and maintenance of photovoltaic power plant, these minor problems should be handled in time to eliminate potential accidents. Can avoid major accidents.
1. Check whether the temperature of equipment, cable and connector is abnormal. During the design of the equipment, the current carrying capacity of copper bars, cables and connectors will have a certain margin. During normal operation, the temperature will not be very high. You can touch the infrared layer with your hands. When the cable ages and the insulation layer is damaged, the local temperature will rise significantly.
2. Pay attention to the changes of current and voltage. When the power generation of a certain line is significantly lower than that of other circuits, but there is no shadow, and the components are also normal. The combiner box shows low voltage and low current, it is necessary to disconnect and check the line until it is completely normal.
3. Pay attention to the change of sound. When the inverter is running, the sound of the fan is stable. When the air duct is blocked or the fan fails, the sound will change. When the insulation layer of the cable is damaged, there will be a sound of metal discharging, and a small spark will also be generated.
4. Pay attention to the change of color. When the photovoltaic power station stops operation, the equipment shell can be disassembled to detect whether the color of each component changes. If the local color of electrical equipment changes, such as turning black, it should be detected and inspected.
5. Pay attention to the change of smell. If there is a smell of paste or burning during the inspection, stop the machine for inspection immediately.
Note: When the equipment is disconnected, it is not allowed to touch bare cables, copper bars and other components with hands immediately. Because the system has large capacity capacitors and other heating components, it is necessary to prevent electric shock and scald, wait for about 30 minutes, and then start the maintenance after the power is discharged and the temperature drops.
