How can the internal cable layout of a photovoltaic box-type substation be optimized to reduce electromagnetic interference and temperature rise?
Release Time : 2026-03-18
Optimizing the internal cable layout of a photovoltaic box-type substation requires addressing two core objectives: electromagnetic interference (EMI) suppression and temperature rise control. This involves scientifically planning cable paths, selecting appropriate laying methods, and strengthening shielding measures to achieve stable system operation. EMI primarily originates from high-frequency signal coupling between cables and the penetration of strong external electric fields, while temperature rise is closely related to cable current carrying capacity, heat dissipation efficiency, and localized heat accumulation. Optimization must consider both factors; for example, reducing the length of parallel cable laying can decrease electromagnetic coupling, while improving ventilation can alleviate temperature rise.
Cable path planning is the primary step in suppressing EMI. High-voltage busbars, as strong interference sources, should maintain sufficient distance from control cables and avoid parallel laying. If space is limited, a vertical cross-layout can be used, with baffles installed at the cross-points to block electromagnetic field propagation. For shared cable trenches or trays, power cables and signal cables should be laid out in layers, with power cables on the lower layer and signal cables on the upper layer, utilizing the shielding effect of the metal trays to reduce interference. Furthermore, when cables are introduced into prefabricated substations, close contact with high-frequency transient current entry points such as surge arresters and capacitive voltage transformers should be avoided to prevent induced voltage from entering the secondary circuit through distributed capacitance.
The choice of laying method directly affects the temperature rise control effect. While direct burial is cheaper, its heat dissipation performance is limited, making it suitable for short-distance, small-section cables. Conduit laying utilizes the thermal conductivity of metal pipes to accelerate heat dissipation, but the conduit diameter must be at least 1.5 times the cable's outer diameter to avoid localized overheating due to limited space. Cable tray laying promotes air convection through its open structure, making it particularly suitable for large-section, long-distance cables. However, care must be taken to ensure that the vertical deviation of the cable tray does not exceed 2/1000 of its length and the horizontal error does not exceed 2/1000 of its width to prevent deformation from hindering heat exchange. For high-temperature environments or high-load scenarios, heat dissipation fins or forced ventilation devices can be added to the cable tray to further improve heat dissipation efficiency.
Shielding measures are a key means of reducing electromagnetic interference. The cable itself should be a shielded cable with a metal sheath, such as the photovoltaic-specific PV1-F cable. Both ends of the shielding layer must be reliably grounded to form a Faraday cage effect, blocking the penetration of external electric fields. For unshielded cables, a metal cover can be added to the termination, and high-frequency interference signals can be short-circuited to ground using a small high-voltage capacitor. For measurement and protection devices in the secondary circuit, a shielding layer must be added between the primary and secondary windings of the current transformers to prevent high-frequency interference from entering the automation system through distributed capacitance. Furthermore, the cabinets and enclosures of prefabricated substations should be made of iron, and copper linings should be added in areas with strong electric fields to enhance shielding against electric and magnetic fields.
Temperature rise control also requires attention to the matching of cable current carrying capacity and heat dissipation conditions. Cable cross-section selection should be based on the long-term allowable current carrying capacity, while also considering short-circuit thermal stability requirements, avoiding overload heating due to an insufficient cross-section. During laying, the cable bending radius must meet standards: not less than 6 times the diameter for unarmored cables and not less than 12 times the diameter for armored cables, to prevent localized overheating caused by mechanical damage. For densely laid areas, cable spacing should be appropriately increased, or thermally conductive silicone should be filled between cables to improve heat transfer efficiency. Regularly cleaning dust and dirt from cable surfaces can prevent abnormal temperature rises caused by impeded heat dissipation.
Electromagnetic compatibility (EMC) design must be implemented throughout the entire cable layout process. Photovoltaic inverters, as a major source of interference, should use twisted-pair or coaxial cables for their output cables, reducing common-mode interference through balanced transmission. Signal transmission lines should be kept away from high-voltage busbars and power cables; filters can be installed where necessary to remove harmonic components generated by the inverter. For photovoltaic-storage-flexible DC-DC interconnected systems, filters must be installed at the converter station output to suppress electromagnetic radiation from DC cables. Simultaneously, optimizing converter valve control strategies can reduce high-frequency interference generated by switching operations.
The application of intelligent monitoring technology provides data support for cable layout optimization. By installing fiber optic temperature sensors or infrared temperature modules at key locations, cable temperature distribution can be monitored in real time, promptly identifying potential localized overheating. Combined with an IoT platform, temperature rise data can be dynamically analyzed to predict cable aging trends, providing a basis for maintenance decisions. Furthermore, the intelligent monitoring system can also monitor electromagnetic interference levels and optimize cable layout through algorithms to achieve coordinated optimization of the electromagnetic environment and temperature rise control.
Optimization of the internal cable layout of a photovoltaic box-type substation must be aimed at electromagnetic compatibility and temperature rise control. This involves scientifically planning routes, rationally selecting laying methods, strengthening shielding measures, matching current carrying capacity and heat dissipation conditions, implementing electromagnetic compatibility design, and applying intelligent monitoring technology to construct a low-interference, low-temperature-rise cable system. This process requires not only theoretical calculations and simulation analysis but also dynamic adjustments based on actual operating conditions to ensure that the cable layout meets the system's stable operation requirements throughout its entire lifecycle.