Design points
- Ground photovoltaic surge protection and grounding
The practical design points of ground photovoltaic lightning protection and grounding are as follows:
1) General grounding layout diagram, component support connection diagram, square grounding diagram, etc.
2) When there is a contradiction between the grounding wire and the equipment foundation, the grounding wire should be laid around the foundation. Each connection point of the ground cable should be soldered firmly to ensure electrical connection. If the ground wire is broken during construction, it should be soldered again.
3) In order to improve the discharge and dissipation capacity of the main grounding grid of photovoltaic power stations, the four corners of the outer edge of the grounding grid should be made into arcs.
4) The grounding construction shall comply with the requirements in the Code for Construction and Acceptance of Grounding Devices for Electrical Device Installation Engineering (GB50169). After the grounding network is completed, the grounding resistance, contact potential and step potential of the grounding network shall be measured, and the measured grounding resistance R shall meet the following requirements: R≤4 ω. If the measured results do not meet the specifications and the design requirements, corresponding measures should be taken until the requirements are met.
5) The buried depth of the horizontal grounding pole should be buried below the frozen soil and not less than 0.8m under the condition that the grounding resistance is not greater than 4 ω, and the distance between the vertical grounding devices should be at least 5m. The bus box should be electrically connected with the main grounding grid and firmly welded with the grounding grid.
6) The base embedded parts on the support should be led out and connected reliably with the main grounding network. The ground terminal reserved for the bus box and the bus box must be soldered.
7) The grounding terminal of the PV module should be reliably connected to the main grounding network.
8) The grounding map of each square array and substation center shall refer to the general grounding layout drawing of the subsquare array grounding layout, and the grounding of the substation center shall be reliably connected to the main grounding network.
9) In order to reduce the surface impact potential, 300mm thick gravel is laid within 3m around the plane of the centralized grounding device.
Clay is used for backfill around all outdoor earthing devices.
10) Grounding construction shall meet GB/T32512-2016 Lightning Protection Technical Requirements for photovoltaic Power Stations.
11) List the grounding materials.
- Lightning protection and grounding of roof photovoltaic
The roof photovoltaic grounding of a project in Hebei is selected as an example. The actual design points are as follows:
1) Draw the general grounding diagram and internal lightning protection and grounding diagram.
2) Roof photovoltaic power station can use roof permanent metal as the connector, but its components should be electrically connected.
3) Contact flash materials refer to GB50057.
4) Steel beams, steel columns, fire ladders and other metal components of the building where the photovoltaic power station is located on the roof of the building and metal columns of the curtain wall can be used as leads, but all components should be electrically connected.
5) Hot dip galvanized round steel or flat steel should be used for special lead line.
6) The equipment and device should be grounded and connected reliably, and overvoltage protection devices should be configured according to the specifications.
7) A material table listing all grounding materials.
- The surface PV is grounded for lightning protection
The surface photovoltaic grounding of a project in Anhui is selected as an example. The actual design points are as follows:
1) The general grounding layout diagram, square grounding diagram, horizontal grounding installation detail diagram, internal lightning protection grounding diagram, etc.
2) Each connection point of the grounding wire should be firmly welded to ensure electrical connectivity. If the ground wire is broken during construction, it should be soldered again.
3) This project is a floating photovoltaic project on the water surface, and photovoltaic module supports shall be erected on the floating tank for safe construction. Because the resistivity of water is extremely low, the grounding resistance of the grounding conductor connected to water must be less than 4 ohms. The horizontal ground bus is used as the equalizing voltage belt of the whole power station, and is finally connected to the anchorage device to guide the abnormal current into the water body. Galvanized steel stranded wire is used as the horizontal grounding bus, which is smaller than the ground hole aperture of the support. It is arranged in the open laying mode, and encircling each photovoltaic square to form a closed ring. All joints shall be hot welded. After forming a ring network, the water surface is discharged at multiple points and grounded at multiple points. The shore grounding is laid according to the path of the collecting line, and is led to the shore ground point for multi-point grounding.
4) The water surface discharge point is recommended to be square array 4 angles, and copper-clad steel stranded wire is used for human water grounding.
5) The grounding construction shall comply with the requirements in the Code for Construction and Acceptance of Grounding Devices for Electrical Device Installation Engineering (GB50169). After the grounding network is completed, the grounding resistance, contact potential and step potential of the grounding network shall be measured, and the measured grounding resistance R shall meet the following requirements: R< 4ω. If the measured results do not meet the specifications and the design requirements, corresponding measures should be taken until the requirements are met.
6) Grounding buses of each square array and box variable floating platform shall be reliably connected with the four Angle anchorage points of the square array anchoring system, and multi-point discharge grounding shall be performed. The box variable grounding terminal shall be reliably connected with the main grounding network.
7) Grounding construction shall meet GB/T32512-2016 Lightning Protection Technical Requirements for photovoltaic Power Stations. The grounding bus should be fixed through the grounding hole of the anchor support when laying around, and through the grounding hole of the equipment support when laying in the middle aisle. Ensure that the bus is beautiful, safe, stable and reliable.
8) The grounding of the equipment meets the specification requirements, and the material table of all grounding materials is listed.
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