Precautions for Design and Installation of Home Photovoltaic Power Generation System

This article mainly summarizes the main issues of the installation and use of distributed photovoltaic power generation systems.

1. Precautions for component installation

2. Design considerations

3. Precautions for electrical connection

4. Precautions for grid-connected inverters

5. Precautions for cables

6. Precautions for combiner boxes and DC and AC power distribution cabinets

7. Precautions for use

01 Precautions for component installation

The electrical installation of photovoltaic modules should refer to the corresponding regulations, including electrical regulations and power connection requirements. For specific terms, please contact the local power department.

Please do not install photovoltaic modules on the roof without safety precautions, including fall protection, ladders and stairs, and personal protective equipment. At the same time, do not install or operate distributed photovoltaic power generation systems in unfavorable environments, such as strong winds and gusty weather, wet and frosted roof surfaces, etc.

When there is light, the photovoltaic power generation system will generate direct current, and the current will increase with the intensity of the light. If you touch the electronic circuit of the component, there will be a risk of electric shock or burns, and a direct current voltage of 30 volts or higher may even be fatal. Therefore, in the process of installation and maintenance, the power supply of the photovoltaic power generation system should be cut off, or they can be moved to a completely dark environment, or the surface of the components can be covered with opaque materials. If operating the system in sunlight, use insulated tools and do not wear metal jewelry.

To avoid arcing and electric shock hazards, do not disconnect electrical connections while working under load. Connector plugs must be kept dry and clean to ensure they are in good working order. Do not insert other metal objects into the plug or make an electrical connection in any other way. Do not touch or handle PV modules with broken glass, detached bezels, and damaged backsheets unless the module is electrically disconnected and you are wearing personal protective equipment. Do not touch wet components.

02 Design Notes

Photovoltaic modules must be installed in suitable buildings or other places suitable for module installation (such as the ground, roof, side facades of houses, etc.); it is generally recommended that photovoltaic modules be installed with an inclination angle of more than 10 degrees so as to play a self-cleaning role when it rains; one piece Or when multiple photovoltaic modules are partially or completely shaded, the system performance will be significantly reduced.

Generally distributed, it is recommended to install the modules in a place without shade throughout the year to increase the power generation of the photovoltaic system. In places where lightning activity is frequent, lightning protection must be installed for photovoltaic systems.

03 Precautions for electrical connection

■ Electrical analysis

Under normal conditions, a photovoltaic module may generate higher current and voltage than under standard test conditions. When the photovoltaic modules are connected in series, the voltage is added; when the photovoltaic modules are connected in parallel, the current is added; the photovoltaic modules with different electrical characteristics cannot be connected in series, and the connection of different electrical components of the photovoltaic modules may cause the mismatch of the electrical connection. Install according to the installation manual.

The maximum number of components that can be connected in series for each row must be calculated according to relevant regulations, and its open circuit voltage value cannot exceed the maximum system voltage value specified by the components and the withstand voltage value of other DC electrical components under the local expected minimum temperature condition.

If a reverse current exceeding the maximum fuse current of the component passes through the component, an overcurrent protection device with the same specification must be used to protect the component. If the number of parallel connections is greater than or equal to 2 strings, an overcurrent protection device must be installed on each string of components.

■Cable and Wiring Installation

Photovoltaic modules have two light-resistant output cables, the terminals of which are connectors, and these plugs can meet most installation requirements.

The positive cable terminal is a female plug, and the negative cable terminal is a male plug. The connecting wire of the module is not only designed for the series connection of the module, but also can be connected with the third-party equipment equipped with the wiring device, and the connection needs to follow the instruction manual of the equipment manufacturer.

When the cables are fixed on the bracket, it is necessary to avoid mechanical damage to the cables or components. To fix the cables, you must use UV-resistant binding wires and wire clips to fix them on the bracket. At the same time, try to avoid direct sunlight exposure and water soaking cables.

■Connector installation

Before connecting the connector, keep it dry and clean, and ensure that the connector cover is firm. At the same time, avoid direct sunlight, soaking in water and placing the plug on the ground or roof surface.

Incorrect connections can cause arcing effects and electric shock. After installation, all electrical connections must be checked for firmness, and at the same time, ensure that all connectors are fully inserted.

■Mechanical connection and installation

General components have been certified for mechanical loads. Static mechanical load that can withstand: the maximum at the back is 2400Pa (wind pressure); the maximum at the front is 5400Pa (snow pressure).

During or after the installation of photovoltaic modules, please do not step on or place heavy objects on the surface of the modules, so as not to cause cracks in the cells.

When designing the support and other mechanical parts, it must be able to withstand the specified maximum wind pressure and snow pressure.

When choosing a grounding method, it must not cause direct contact between the frame of the photovoltaic module and other metals, so as to avoid the occurrence of electrical corrosion.

In order to maintain the fire rating, the distance between the glass surface of the photovoltaic module and the roof surface should be at least 10cm. The distance between installed adjacent photovoltaic modules must be at least 2cm.

04 Precautions for grid-connected inverters

■Safety Precautions

Non-professionals are prohibited from touching photovoltaic equipment such as inverters;

Pay special attention to the installation site and condition requirements of the inverter specified in the IEC-60364-7-712:2002 standard;

Before maintenance and repair of the photovoltaic system, all power supplies must be disconnected to avoid safety accidents;

Ensure that the grounding device and short circuit protection device of the inverter are safe and reasonable;

When overhauling or maintaining the inverter, please disconnect it from the power grid through the communication system, and then disconnect the DC line to avoid electric shock injury;

When you are overhauling or maintaining the inverter, please wear labor protection supplies, such as insulated shoes, insulated gloves, etc. At the same time, you also need to pay attention to the following items:

●Do not touch electrical connection points; do not wear any metal jewelry;

●Inverters under changing working environment must comply with relevant national standards;

The inverter must strictly abide by the product instruction manual, and it is strictly forbidden to use it in a space with a relative humidity > 95% in an explosive environment;

●Do not touch the cooling device of the inverter to avoid burns.

■Inverter installation location and assembly precautions

Do not install the inverter near flammable and explosive items;

Ensure that the installation area of the inverter and the fuse box is dry and the air circulation is good;

In order to ensure the peak performance of the equipment, the maximum ambient temperature needs to be considered;

In order to avoid voltage reduction due to overheating, therefore, do not expose the inverter;

If the inverters are to be installed in high temperature areas, the distance between inverters must be enlarged and sufficient air circulation must be ensured. Prevent its output power from being reduced due to excessive temperature;

Never block the ventilation device of the inverter;

The assembly location must be freely accessible without additional brackets or lifting platforms; the assembly location and assembly method must be adapted to the size and weight of the inverter; the assembly surface must be solid and fireproof.

The installation height of the inverter must be reasonable, the air inlet (bottom) of the inverter is 600mm from the ground, and the air outlet (top or side of the machine) is 400mm. Keep well ventilated. The inverter is best installed in a cool place to prevent exposure to the sun from affecting the work of the machine. It is recommended to install it in a place with a good surrounding environment to prevent dust and debris from blocking the fan.

The power distribution room where the inverter is installed. The location of the power distribution room should be as close as possible to the solar cell array and users to reduce line loss. For small and medium-sized inverters, they can be fixed on the wall or placed on the workbench according to requirements; large-scale inverters are generally placed directly on the ground, and a certain distance should be left between them and the wall for wiring and maintenance. Allows for ventilation. Be careful not to shine the sun directly on the inverter. If the inverter is to be installed outdoors, sealing and moisture-proof measures must be taken.

■Precautions for electrical connection

When the inverter starts and stops, its terminals and cables will generate voltage, so it must be installed by qualified professional technicians;

All cables connected to the inverter must be suitable for system voltage, current and environmental conditions (temperature, UV);

The rated voltage is 1.8kV (core to core, non-grounded system, no loop under load). If the cable is used in a DC system, the rated voltage between the conductors should not be greater than 1.5 times the AC rated value U of the cable. In a single-phase grounded DC system, this value should be multiplied by a factor of 0.5;

During the connection process, pay attention to the correct pulling and connection of all cables;

A good ground connection must be ensured;

Before making electrical connections, it must be ensured that the inverter has been fixedly installed;

Disconnect the AC or DC voltage sequence: first disconnect the AC voltage, then disconnect the DC voltage.

■Maintenance Precautions

Regularly clean the dust on the inverter box. It is best to use a vacuum cleaner or a soft brush when cleaning, and only use dry tools to clean the inverter;

If necessary, remove the dirt in the air vent to prevent the dust from causing excessive heat and resulting in performance loss;

Check the surface of the inverter and cables for damage, and a professional electrician must repair the connection of the inverter cables;

The connection of the cabinet to the ground should be firm and reliable;

When doing internal repairs, keep in mind that when the inverter is turned on or disconnected, the maintenance work needs to be done by an authorized professional electrician. Because, the cap or the end may generate a lethal voltage.

05 Cable Precautions

1. The wiring installation must be in the charge of professional technicians; when connecting the wiring, it must be based on the size, model and manufacturer required by the design drawings;

2. When connecting the lines, consider the final connection part of the wires, and leave a certain margin; do not abuse the cables, and it is strictly forbidden to use the cables in places beyond their carrying range;

3. Cable trays should be stored in different categories to avoid deformation due to external forces; the appearance should be undamaged and well insulated; direct-buried cables and underwater cables should pass relevant tests before they can be used; the wiring of the phalanx components should be completed according to the construction drawings Check whether the wiring is correct; after the wires pass through the conduit, the nozzle should be waterproofed according to the design requirements;

4. During construction, the bending radius of the cable should not be less than 4 times the outer diameter of the cable; the laying temperature should not be lower than 0°C.

06 Precautions for combiner boxes and DC and AC power distribution cabinets

1. The combiner box can generally be installed in the power distribution room or on the square bracket according to the actual situation of the project; the installation position of the equipment should meet the design requirements; the vertical deviation of the cabinet installation should not exceed 2mm; the control cabinet installed outdoors should be firmly fixed on the On the bracket or platform; the cabinet body should provide the specifications consistent with the corresponding company;

2. The cabinet shell should be selected according to the corresponding standard principles, and the appropriate protection level should be selected according to the different installation locations;

3. The shell of electrical equipment should provide corner protection to prevent mechanical or other impacts caused by appearance; the outer packaging of electrical equipment and power distribution cabinets must be waterproof, ensure airtightness, and prevent water vapor and the entry of dust.

07 Precautions for use

1. After the photovoltaic module has been running for a long time, dust or dirt will be deposited on the surface of the module, which reduces the power output of the module. It is generally recommended to clean the modules regularly to ensure their maximum power output, especially in places where there is less precipitation, and more attention should be paid to the cleaning of the modules.

2. In order to reduce potential electrical shock or thermal shock, it is generally recommended to clean the modules in the morning or late in the afternoon, because the solar irradiance is weaker and the temperature of the modules is lower at that time. Especially in places with high temperature, more attention should be paid.

3. General photovoltaic modules can withstand a frontal snow load of 5400Pa. When removing snow on the surface of photovoltaic modules, please use a brush to gently remove the snow. Ice frozen on the surface of PV modules cannot be removed.

Do not clean photovoltaic modules with broken glass or exposed cables to avoid danger.

Generally, it is recommended to use a soft brush and clean and mild water to clean the glass surface of photovoltaic modules. The force used should be less than 690Kpa, which meets the standards of the municipal cleaning work system.