When working in an independent power supply system, you need to understand the following basic points:
(1) Keeping vigilance, comprehensive inspection and careful work is the best security system.
(2) Never work alone.
(3) Learn and understand the system before starting work.
(4) Before installation and commissioning, review every safety, test and installation procedure.
(5) Ensure the correct working sequence of tools and test equipment.
(6) Be sure to check the test equipment before entering the work site.
(7) Wear suitable protective clothing, including safety helmets and eye protection equipment.
(8) Remove all jewelry that may conduct electricity with electrical components.
(9) ELV DC voltage can produce a significant arc, such as a wet hand touching a higher voltage will cause a tingling sensation.
(10) Wear dry insulating gloves when working with electricity.
(11) Measure all electrical parts, such as checking whether the connection between the bare metal frame and the cabinet is grounded, measuring the voltage of each wire to the ground, and measuring the operating voltage and current.
(12) Be aware of risks. It cannot be considered that the switch is always effective, that the actual configuration is always consistent with the power chart, and it cannot be assumed that there is no short circuit in the ground loop.
①Photovoltaic modules
Photovoltaic equipment can generate electricity and should always be considered “active” because it generates electricity as long as there is light on it. Trying to cover the photovoltaic module with a blanket or cardboard does not guarantee a safe shutdown of the power generation state, because the light can still reach the photovoltaic module, and the obstruction may also fall.
In large-scale independent systems, the DC voltage of some photovoltaic arrays exceeds 120V (LV). This voltage level can cause danger to people. Any installation and maintenance personnel need to be qualified as electrical engineers. Before any work starts, it may be necessary to isolate the PV strings to maintain the voltage within the safe voltage range (ELV).
Since the photovoltaic module is also connected to the energy storage battery, it is sometimes necessary to test whether the module remains connected to the energy storage battery. Cutting off the output of the photovoltaic module will cause sparks or arcs. When the energy storage battery is connected, cutting off the output of the photovoltaic module will potentially cause the cut off battery to generate a large current. Although the current can be blocked by fusing, it may not be able to rely on it in the protection of the field system.
If possible, ensure that all photovoltaic equipment is kept isolated before starting work.
Photovoltaic modules have an aluminum frame, which is mounted on the bracket of the metal array and fixed with a metal base. These metal parts will heat up under the sun during the day and sometimes burn the skin, so it is necessary to wear gloves and protective clothing.
Photovoltaic modules are often installed on roofs or tall buildings. The ladders for work must be firm, and safety belts or scaffolding should be used.
②Battery
The independent power supply system includes immersed or sealed lead-acid batteries, and any operation must be performed to keep the battery pack in an isolated state.
The battery terminal needs to be covered with a cover, and insulating tools (such as a wrench, etc.) should be used to prevent short-circuiting of the battery terminals when working.
For larger systems, the voltage of many battery packs belongs to the LV level, which can cause danger to people, and any installation and maintenance personnel need to be qualified as an electrical engineer. Before any operation starts, it may be necessary to isolate the battery pack to reduce its voltage to the ELV level.
The sulfuric acid in lead-acid batteries can cause chemical burns when it comes in contact with the eyes and skin.
Hydrogen is released when the battery is charged, which also occurs when the “sealed” battery is overcharged. Hydrogen is an explosive gas. Be vigilant when working near the battery and maintain good ventilation. There should be no open flames or sparks during the operation to avoid explosion.
Most batteries are heavy (usually more than 30kg), so they should not be moved by one person. To move the battery, a check-in truck or other suitable transportation equipment must be used. The lifting of the battery needs to follow standard actions, such as ensuring that the back is straight and the legs are bent.
③Internal combustion generator
The fuel used in internal combustion generators is flammable or combustible, and potentially explosive. Care must be taken to ensure that there is no open flame near the fuel.
The generator used in the hybrid power system is usually controlled by an automatically-started device. Before performing any operation, it should be ensured that the generator’s automatic-starting device is disabled. Do not wear loose clothing when working near a running generator. Fuel generators usually generate 240V alternating current. Work involving generator power output must be performed by a professional electrician, and all relevant safety regulations must be observed.
Because the generator is heavy, it is not suitable to be moved by a single person. When moving the generator, a consignment truck or other suitable transportation equipment must be used.
④Wind generator
Wind turbines are rotating devices installed on tall towers. Some towers are tiltable, and some require ladders to reach the generator.
The installation of the tower must be operated by a licensed assembler and must comply with the relevant national occupational health and safety regulations. You need to be careful when working on a sloping tower, and you must be sure to ascend and descend in a safe way. Be careful when climbing a fixed tower. If there is no safety barrier around the ladder, you must wear a seat belt.
Many wind turbines produce three-phase low-voltage AC output, which is used to charge the battery after current conversion. All low-voltage work must be performed by a licensed electrician and comply with relevant safety regulations.
Wind turbines are usually equipped with a set of braking system to ensure that the generator stops running during maintenance. In any maintenance situation, the generator rotor and blades must be locked.
⑤Micro hydroelectric generator
Micro hydroelectric generators are located beside streams and rivers, and their locations are often slippery, so be careful. Make sure that the generator cannot rotate during installation or maintenance work. Micro-hydrogenerators are also rotating devices. Do not wear loose clothing when working near the micro-hydrogenerators in operation.
Some micro-hydrogenerators can produce three-phase low-voltage AC output, which is used to charge the battery after current conversion. All low-voltage work must be performed by a licensed electrician and comply with relevant safety regulations.
Most micro hydroelectric generators are heavy, so they should not be carried by individuals. The movement of the generator should be carried out using a consignment truck or other suitable hoisting/moving equipment.