[Problems to be noted in the application and design of box type substation]: 1 Overview and application of box type substation, also known as outdoor complete substation, also known as combined substation, is widely valued because of its advantages such as flexible combination, convenient transportation, migration, convenient installation, short construction period, low operation cost, small floor area, pollution-free, maintenance free, etc. Rural network construction
Overview and application of box type substation
Box type substation, also known as outdoor complete substation, also known as combined substation, is widely valued because of its advantages such as flexible combination, convenient transportation, migration, convenient installation, short construction period, low operation cost, small floor area, pollution-free, maintenance free, etc. In the construction (transformation) of rural power grid, it is widely used in the construction and transformation of urban and rural 10~110kV small and medium-sized substations (distribution), factories and mines, and mobile operation substations. Because it is easy to go deep into the load center, reduce the power supply radius, and improve the terminal voltage quality, it is especially suitable for the transformation of rural power grid, and is known as the target mode of substation construction in the 21st century.
Characteristics of box type substation
1.1.1 Advanced technology and safety * The box part adopts the current domestic leading technology and process, the shell is generally made of aluminum zinc plated steel plate, the frame is made of standard container materials and manufacturing process, which has good anti-corrosion performance and can ensure that it will not be rusted for 20 years, the inner sealing plate is made of aluminum alloy gusset plate, the interlayer is made of fireproof and thermal insulation materials, the box is installed with air conditioning and dehumidification devices, and the equipment operation is not affected by the natural climate environment and external pollution, It can ensure normal operation under the harsh environment of – 40 ℃~+40 ℃. The primary equipment in the box is the unit vacuum switch cabinet, dry-type transformer, dry-type transformer, vacuum circuit breaker (spring operating mechanism) and other domestically advanced equipment. The product has no exposed live parts. It is a fully insulated structure, which can completely achieve zero electric shock accidents. The whole station can realize oil-free operation with high safety. The secondary computer integrated automation system can realize unattended operation.
1.1.2 The intelligent design of the whole station with high degree of automation. The protection system adopts the microcomputer integrated automation device of the substation, which is installed in a decentralized manner, and can realize the “four remotes”, namely, telemetering, remote signaling, remote control and remote adjustment. Each unit has independent operation functions. The relay protection functions are complete. It can set the operation parameters remotely, control the humidity and temperature in the box, and meet the requirements of unattended operation.
1.1.3 During the factory prefabricated design, as long as the designer makes the primary main wiring diagram and the design of equipment outside the box according to the actual requirements of the substation, he can choose the specifications and models of the box transformer provided by the manufacturer. All equipment is installed and debugged in the factory once, which truly realizes the factory construction of the substation and shortens the design and manufacturing cycle; On site installation only requires box positioning, cable connection between boxes, outgoing cable connection, protection setting verification, drive test and other work requiring commissioning. The whole substation only takes about 5-8 days from installation to operation, greatly reducing the construction period.
1.1.4 Flexible combination mode The box type substation has a compact structure, and each box forms an independent system, which makes the combination mode flexible and changeable. We can adopt the box type substation, that is, 35kV and 10kV equipment are installed in all boxes to form a full box type substation; 35kV equipment can also be installed outdoors, and 10kV equipment and control and protection system can be installed inside. This combination mode is especially suitable for the reconstruction of old substations in rural power grid reconstruction, that is, the original 35kV equipment is not moved, and only a 10kV switch box can be installed to meet the unattended requirements.
1.1.5 Investment saving and effective fast box type substation (35kV equipment is arranged outdoors and 10kV equipment is installed inside the box) reduces investment by 40%~50% compared with the integrated substation of the same scale (35kV equipment is arranged outdoors and 10kV equipment is arranged in indoor high-voltage switch room and central control room).
1.1.6 The above example shows that the floor area of the substation is reduced by about 70m2 due to the box type substation without building quantities, which conforms to the national land saving policy.
1.2 Application of box type substation in rural power grid construction (transformation) The box type substation mode is widely used in rural power grid construction (transformation). For example, a new 35kV terminal substation with main transformer capacity of 2 × 3150kVA, three-phase double winding non excitation voltage regulating power transformer with voltage grade of 35 ± 2 × 2.5％/10.5kV。
One circuit of 35kV overhead incoming line, 35kV vacuum load disconnector and fast fuse are used together at the high-voltage side of the main transformer to replace 35kV vacuum circuit breaker, reduce the cost, and realize linkage opening when the fuse is fused in one phase and in phase failure operation. The 10kV part adopts the layout of box type power distribution station. There are 6 outgoing lines of 10kV cables, one of which is reactive compensation circuit and the other is standby. The 35kV and 10kV buses are connected by single bus without section. The substation is set at the 35kV incoming line side, with a capacity of 50kVA and a voltage level of 35 ± 5%/0.4kV. The electrical secondary system of the box type distribution station adopts a microcomputer integrated automation system.
[$page] 2 Considerations in the design of box type substation
2.1 The minimum fire protection clearance between the main transformer and the box shall meet the requirements of Code for Design of 35~110kV Substation, and the minimum fire protection clearance between buildings with fire resistance rating of Class II and the transformer (oil immersed) shall be 10m. For the external wall facing the transformer, combustible dielectric capacitor and other electrical equipment (meeting the firewall requirements), if there are no doors and windows or holes within the total height of the equipment plus 3m and 3m on both sides, the clear distance between the wall and the equipment can be unrestricted; If no general doors and windows are opened within the above range, but there are fire doors, the clear fire distance between the wall and the equipment shall be equal to or greater than 5m. The minimum fire resistance rating of the power distribution device is Grade II. The primary system inside the box of the box type power distribution station adopts the unit vacuum switch cabinet structure. Each unit adopts the door structure decorated with special aluminum profiles. The rear of each bay is equipped with double-layer protective plates, which can open the external door. In our design work, the minimum fire protection clearance between the main transformer and the box is recommended to be 10m to ensure the safe operation of the substation.
2.2 The 10kV cable outlet shall be laid through steel pipes for aesthetic purposes. The surrounding area of the 10kV box type distribution station box in the substation is generally designed as cement pavement, and the 10kV line terminal pole is generally 10m outside the substation wall. If the cable is directly buried and led to the line terminal pole, it will bring great inconvenience to the maintenance. Therefore, 10kV cable outlet shall be laid through steel pipes to facilitate maintenance and repair of users. If the 10kV line terminal pole is far from the substation, the 10kV cable outlet from the box to the enclosure of the substation must be laid through steel pipes. A new type of over-voltage protector is installed on the line terminal pole at the end of the cable outgoing line to prevent over-voltage.
3 Conclusion
In recent years, the box type substation is the main direction of rural power grid construction (transformation) and future substation construction, but there are still some shortcomings, such as small expansion margin of outgoing line interval in the box, small maintenance space, etc. However, it is widely promoted and used with the advantages of economy and practicality, and its shortcomings will be improved and perfected in the continuous development.
Post time: Oct-22-2022