Against the background of new power system construction, urban and rural distribution network upgrading and new energy grid connection, prefabricated substations, as highly integrated complete power distribution equipment, have gradually replaced traditional civil engineering substations by virtue of factory prefabrication, rapid on-site deployment, small floor area and low investment cost.

Defined by national standard GB/T 17467 High/Low Voltage Prefabricated Substation, it integrates high-voltage switchgear, power transformer, low-voltage distribution devices, protection monitoring system and auxiliary facilities into one or more closed metal boxes according to fixed wiring schemes. All assembly, wiring and commissioning are completed in factory. After overall transportation to site, it can be put into operation only through simple hoisting and cable connection.

First emerging abroad in the 1960s and introduced to China in the late 1970s, prefabricated substations have formed a complete product series after decades of technological upgrading, widely applied in urban distribution networks, residential communities, industrial parks, new energy power stations, rail transit and other diversified scenarios. This paper comprehensively introduces its definition, working principle, structure, classification, application, selection, installation, maintenance and development trend.

1. Definition and Working Principle

The core feature of prefabricated substation is factory integration and fast field installation. It concentrates three core functional areas of traditional substations: high voltage room, transformer room and low voltage room into sealed box body to realize one-stop power distribution solution.

Its basic function is consistent with traditional substations, undertaking voltage transformation, power distribution, fault protection and operation monitoring, serving as key link connecting high-voltage power grid and terminal power consumption equipment.

Working Process:

1. High Voltage Access: 10kV/35kV high-voltage power is connected into high voltage chamber, controlled and protected by high-voltage switches and fuses.

2. Voltage Transformation: High voltage power flows into transformer chamber, converted into 0.4kV low voltage power by oil-immersed or dry-type transformer based on electromagnetic induction principle.

3. Low Voltage Distribution: Converted low voltage power is distributed to each power load through low voltage cabinets, circuit breakers and distribution equipment.

4. Safety Monitoring & Protection: The intelligent protection system monitors real-time current, voltage and temperature, automatically cuts off faulty circuit in case of overload, short circuit and overheating to ensure safe operation.

2. Main Structural Composition

2.1 Box Shell

It is the outer protective carrier of the whole equipment, mainly made of galvanized steel plate, stainless steel and SMC composite material, with protection level above IP43, good rainproof, dustproof and anti-corrosion performance.

The interior adopts partition layout, dividing independent high voltage area, transformer area and low voltage area, safe for operation and convenient for maintenance.

2.2 Core Electrical Components

1.High Voltage Components: Including ring main unit, load switch, isolating switch, grounding switch and high voltage cable accessories, used for high voltage circuit control and fault protection.

2.Transformer: The core voltage conversion unit, divided into oil-immersed transformer for outdoor large load and dry-type transformer for indoor dense population and fire-proof occasions. Common capacity range: 30kVA~2500kVA.

3.Low Voltage Components: Including low voltage distribution cabinet, air circuit breaker, reactive power compensation device, electric energy meter and leakage protector, realizing power distribution, electric energy metering and power quality optimization.

2.3 Auxiliary System

1.Heat Dissipation System: Natural heat dissipation for oil-immersed transformer; natural air cooling or forced air cooling for dry-type transformer.

2.Monitoring & Protection System: Temperature controller, smoke alarm, relay protection and remote communication module, supporting remote data transmission and early warning.

3.Other Accessories: Earthing device, maintenance lighting, hoisting parts and drainage facilities to guarantee stable field operation.