Will introduce the general dangerous points that appear when carrying out the work related to the independent power generation system.
① Personal injury (non-electrical, non-chemical)
People working in photovoltaic power stations will be outdoors, even in remote areas. There may be cases where manual and electric tools are used on metal or wire equipment. Workers will also work on batteries, which may cause burns, shocks and physical injuries.
(1) Exposure injury
If the design is reasonable, the photovoltaic array will be installed in a place with the strongest sunlight and no obstructions.
When working near the photovoltaic array, the staff should wear a hat, long-sleeved trousers, and use a sufficient amount of sunscreen. In summer, you should add enough water, not drink alcohol, and take a few minutes of regular rest under the shade every hour; in winter, you should keep warm and wear gloves.
Wind turbines (micro-hydrogenerators, or smaller ones) installed in exposed locations should also follow the above recommendations.
(2) Snake and insect damage
Spiders and a large number of insects (including wasps) often move and live in junction boxes, array frames, and other accessories of independent power generation systems. Snakes often hide in the shade under the array, and ant colonies often move around the battery box or under the array. Therefore, workers should be prepared when opening the junction box and other enclosures, and must carefully observe the surroundings when they need to crawl or crawl under the photovoltaic array.
(3) Cuts or bruises
Most photovoltaic arrays use metal frames, junction boxes, bolts, nuts, cables, and anchor bolts. Many of these common items have sharp edges. If you are not careful, you may be injured. Wear gloves when handling metals, especially drilling and cutting. Metal fragments on the drill bit are often left near the edge of the hole. If it is operated with bare hands, it may cause severe cuts. Wear a safety helmet when working under the array or when there is hardware above the head in the system.
(4) Fall, sprain and strain
Many independent power supply systems are installed in remote areas and the surrounding terrain is rugged. When going to the scene or walking around the scene, especially when carrying system components and test equipment, it may cause falls or sprains. Therefore, it is best to wear comfortable shoes with soft soles. Steel-toed shoes should not be worn near the independent power supply in operation, because they reduce the resistance of the potential current path, but should be worn during installation work before commissioning.
Be careful when lifting and carrying heavy equipment, especially batteries. Use your legs instead of your back to avoid straining your back. If you need to climb, you must ensure that the ladder is firm, and there should be a companion who can hold the ladder to assist in the transportation. In addition, on a windy day, the photovoltaic module can lift people off the ladder like a sail.
(5) Thermal burn
The temperature of metal objects exposed to sunlight can reach 80°C, which is too high to be touched, but if you can quickly remove your hands, it is unlikely to cause burns. For safety reasons, it is best to wear gloves when working on photovoltaic arrays in summer. Before starting work, check for any equipment in the system that may generate heat.
②Electrical damage
Many common electrical accidents can cause electric shocks or burns, which may cause shock-induced muscle contractions and traumatic injuries. These damages occur when current flows through the human body, and the magnitude of the current is determined by the potential difference (voltage) and the resistance of the current path. Under low frequency alternating current (50Hz or lower), the human body is like a resistor, but the resistance value changes with conditions.
It is difficult to estimate when the current will flow and the severity of the injury that may occur, because the resistivity of human skin can vary from less than 1,000 Ω to hundreds of thousands of Ω, which mainly depends on skin moisture.
Alternating current that is only slightly larger than 0.02A through the human body will be very dangerous, because you may not be able to break away from the current-carrying wire. If it is direct current, this kind of damage will be more serious, because direct current does not regularly return to zero.
When the voltage is as low as 20V, even a small current will be forced through wet hands. If the voltage is increased again, the possibility of current passing is greater. High-voltage electric shock (greater than 400V) will burn the protective layer of the skin at the skin contact. When such an accident occurs, the resistance of the body is reduced, and the fatal current will cause immediate death of the person.
Electric shocks are painful, and possible minor injuries are usually exacerbated by the reflex response of the body struggling to escape the source of contact.
The best way to avoid electric shock is to frequently measure the voltage between any conductor and wire and the ground voltage, and measure the current with a clamp-on ammeter. Never disconnect the wires before measuring the voltage and current, don’t think that everything is connected and operating as designed, don’t believe that the switch can always operate flexibly, and don’t trust the indicator diagram too much. Electronic voltmeter is a very good instrument, using it may save your life.
Regarding AC hazards.
Alternating current is generated by inverters, fuel generators, and some micro hydroelectric generators and wind generators. The output of inverters and fuel generators is generally 240V alternating current, and the voltages of hydroelectric generators and wind generators can be different, but they are usually more than 50V alternating current. These are lethal voltages, and the exposed terminals should not be touched in the field.
Note: Unlicensed electrical contractors (or electricians) can only work on ELV (below 120V, DC) circuits. Operations on AC lines above 50V and all ripple-free DC circuits above 120V must be performed by qualified electricians with appropriate training.
③Chemical damage
⑴Acid burns
Independent power generation systems use batteries. A large proportion of these batteries are of the lead-acid type and use sulfuric acid as an electrolyte. Sulfuric acid is very dangerous. It may overflow. When the battery is charged, acid mist may also be sprayed. If the acid comes into contact with unprotected parts of the body, chemical burns will occur (eyes are particularly vulnerable), and the acid will burn on clothing. Out of the hole. When working around lead-acid batteries, you should wear non-absorbent gloves, protective glasses, and neoprene coated aprons.
⑵Gas explosion or fire
Most batteries used in independent power generation systems release hydrogen during charging. This combustible gas is hazardous. All flames and equipment that may generate sparks (controllers with relays, etc.) should be kept away from the battery as much as possible. The battery should be placed in a well-ventilated place.