The installation of a prefabricated photovoltaic substation is a systematic and standardized process. Its core features are "modularization" and "factory prefabrication and on-site assembly". Therefore, compared with traditional civil substations, the installation cycle is greatly shortened, but the process and requirements are more sophisticated.
1. Pre-Installation Preparation
This is crucial to ensuring a smooth installation, accounting for approximately 30%-40% of the total project effort.
Ⅰ.Technical disclosure and drawing review:
Organize a detailed technical briefing with the construction company, design company, prefabricated cabin manufacturer, construction company, and supervision company.
Carefully review the prefabricated cabin layout, foundation drawings, electrical wiring diagrams, and grounding diagrams to ensure that all participating parties have a consistent understanding of the design intent and technical requirements.
Ⅱ.Site survey and site leveling:
Check that the installation site meets design requirements, including location, area, and slope.
Level and compact the site to ensure a solid and level foundation. Plan transportation routes and lifting areas.
Ⅲ.Foundation Construction:
This is the most critical step. Construction must strictly follow the foundation drawings provided by the prefabricated cabin manufacturer.
Foundation Type: Typically a reinforced concrete strip foundation or a monolithic slab foundation. Grounding flat steel and embedded components (anchor bolts or embedded steel plates) for cabin attachment must be pre-embedded in the foundation.
Precision Requirements: The elevation, levelness, and spacing of embedded components must be extremely precise. Any deviation will result in the prefabricated cabin not being properly positioned or providing a tight seal. Re-measurements must be performed after completion.
Ⅳ.Equipment Unpacking and Inspection:
Upon arrival of the prefabricated cabin, an unpacking inspection will be conducted in the presence of the client, supervisor, and manufacturer.
Inspection Details: Check the cabin's exterior for transport damage, deformation, or paint peeling; verify that the equipment model, quantity, and accessories are consistent with the contract; and check that all accompanying documentation (certificate of conformity, factory test report, manual, drawings, etc.) is complete.
Ⅴ.Construction Resource Preparation:
Personnel: Qualified lifting supervisors, riggers, electricians, and installers.
Machinery: An appropriately sized crane (typically 25 tons or more), a forklift, hydraulic wrenches, and other tools are available.
Supplies: Copper busbars, cables, grounding wires, and fasteners are required for installation.
2. Main Installation Steps
Step 1: Positioning and Leveling the Cabin
◆Lifting:
Use a crane and specialized lifting equipment (usually at four lifting points on the cabin roof) and perform a smooth lifting operation under the direction of a professional rigger.
During the lifting process, keep the cabin level and move slowly to avoid excessive shaking or collisions.
◆Positioning:
Gently lower the hull onto the foundation, aligning it with the embedded hardware or anchor bolt holes.
◆Leveling and Securing:
Use tools such as jacks and shims to fine-tune the hull's levelness and elevation.
After confirming levelness, securely fasten the hull bottom to the embedded hardware with bolts, ensuring the torque meets the manufacturer's specifications. Finally, perform a secondary grouting and seal with high-strength cement mortar.
Step 2: Grounding System Installation
Safety is paramount! PV power stations are at high risk of lightning strikes, so reliable grounding is essential.
Reliably weld the grounding terminal provided on the pod base to the grounding flat steel embedded in the foundation at at least two locations.
Apply anti-corrosion treatment (apply asphalt paint or anti-corrosion paint) to the welded areas.
The grounding grid (grid grounding) throughout the substation must form a complete electrical path, with a grounding resistance of less than 4 ohms (usually higher, depending on the design).
Step 3: Connecting Cabins and Cable Trench Connections (Multiple Cabin Combinations)
If multiple prefabricated cabins are combined into a substation, first position and level each cabin.
Then, loosen the protective plates on the joint surfaces and bolt the adjacent cabins together to ensure mechanical strength and a tight seal (using sealing strips).
Connect the cable trenches or cable trays between the cabins to ensure the cable routing path is clear and sealed to protect against small animals.
Step 4: Internal Equipment Inspection and Wiring
Internal Inspection: Open the cabin door, ventilate, and inspect internal equipment (transformers, switchgear, etc.) for looseness, displacement, or damage after transportation.
Busbar Connection: Connect the main busbars between the high-voltage cabinet, transformer, and low-voltage cabinet within the cabin. Before connection, clean the contact surfaces, apply electrical compound grease, and tighten with a torque wrench to the specified torque to minimize contact resistance.
Secondary Wiring: Connect secondary cables for control, measurement, and protection. Wiring should be accurate, secure, and aesthetically pleasing, with clear labeling.
Step 5: External Cable Connection
Route the DC cables from the PV array and the AC cables to the grid into the cabin through the reserved cable holes.
Note: The cable entry holes must be tightly sealed with fireproof putty to prevent the ingress of rain, dust, and small animals.
Step 6: Final inspection and debugging
◆Electrical Inspection:
Insulation Resistance Test: Measure the insulation resistance of the primary and secondary circuits to ground, which must meet specifications.
Circuit Resistance Test: Measure the contact resistance of the main circuit, which must meet specifications.
Relay Protection Commissioning: Set parameters and verify the functionality of the protection devices.
Phase Verification: Ensure the correct phase sequence.
◆No-load Test Run: After all inspections pass, power on the equipment for a no-load test run to check for abnormal noise, heat generation, and other phenomena.
◆Load Test Run: Gradually increase the load and monitor various operating parameters (voltage, current, temperature, etc.) for normal operation.
3. Precautions and Common Problems
◆Weather Factors: Avoid performing lifting and electrical work in inclement weather such as rain, snow, and strong winds.
◆Prevent Moisture and Condensation: After the prefabricated cabin is in operation, condensation is very likely to form due to the temperature difference between the inside and outside. Ensuring that the air conditioning system, dehumidifier, electric heater, and other environmental control systems are functioning properly is crucial to ensuring the long-term stable operation of the equipment.
◆Fire Safety: The cabin should be equipped with a qualified smoke and temperature alarm system and an automatic fire extinguishing device (usually gas fire extinguishing).
◆Ventilation and Heat Dissipation: Ensure that the cabin's ventilation openings are unobstructed and the fan is operating properly to prevent equipment degradation or damage due to overheating.
◆Strictly Follow the Manual: All installation and commissioning work must strictly follow the installation instructions and technical specifications provided by the equipment manufacturer.
Summary
The installation process for a prefabricated photovoltaic substation can be summarized as: "Careful preparation → Precise foundation → Smooth installation → Reliable grounding → Tight wiring → Rigorous commissioning." The quality of installation is directly related to the safety, stability, and lifespan of the entire photovoltaic power station. Therefore, selecting an experienced construction team and maintaining close technical communication with the prefabricated substation manufacturer are crucial to a successful installation.
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