Basic Knowledge of Compact Substations: Structural Composition, Working Principle, and Application Scenarios

A compact substation (abbreviated as "compact substation") is a prefabricated power distribution device integrating high-voltage switchgear, transformer, and low-voltage distribution equipment. Compared with conventional civil substations, the footprint of a compact substation of the same capacity is only 1/10 to 1/5 of the traditional solution, greatly reducing design and construction workload. It is currently the main equipment for urban and rural distribution network construction.

I. What is a Compact Substation

A compact substation is a compact complete power distribution device that combines 10kV (or 35kV) high-voltage switchgear, distribution transformer, and 0.4kV low-voltage distribution equipment in a certain wiring scheme, installed inside a metal enclosure. Its core features are high integration, factory prefabrication, and plug-and-play operation.

The product complies with the national standard GB/T 17467 "High-voltage/low-voltage prefabricated substations" and is divided into two major categories: European type (YBM series) and American type (ZGS series). In the domestic market, European-type compact substations are the mainstream.

II. Structural Composition

The interior of a compact substation is usually divided into three independent compartments:

High-voltage Compartment

Equipped with high-voltage switchgear, typically load switch + fuse combination unit (ring network cabinet solution) or circuit breakers. Used to control the 10kV incoming line and transformer protection. The high-voltage cabinet type is selected as KYN28 medium-voltage cabinet, XGN fixed cabinet, or SF6 ring network cabinet according to the system scheme.

Transformer Compartment

Houses the distribution transformer (oil-immersed or dry-type), with capacity typically ranging from 50kVA to 2500kVA. Equipped with temperature monitoring devices and heat dissipation ventilation systems. Dry-type transformers have seen increasing application in recent years due to safety and environmental advantages. The transformer compartment is provided with natural ventilation or forced air cooling channels to ensure the transformer operating temperature stays within normal range.

Low-voltage Compartment

Equipped with low-voltage distribution cabinets (GGD, GCS, or MNS type) for 0.4kV power distribution and control. Includes main incoming switch, feeder switches, capacitor compensation devices, and metering units. Intelligent instruments and remote monitoring terminals can be configured as needed.

III. Working Principle

10kV high-voltage power is introduced into the high-voltage compartment of the compact substation via cables or overhead lines, then connected to the primary side of the transformer through load switches (or circuit breakers) and fuses. The transformer steps down 10kV to 0.4kV, outputs to the low-voltage compartment, and is distributed through distribution cabinets, then supplied to users via multiple cable feeders. The fuses provide short-circuit protection for the transformer, while load switches enable normal operation and fault isolation.

All high- and low-voltage equipment and transformers inside the compact substation are connected by copper bars or cables. All electrical connections are completed at the factory; on-site work only requires connecting incoming and outgoing cables for commissioning.

IV. Technical Parameters

V. Typical Application Scenarios

• Urban distribution networks: used for 10kV ring network power supply and terminal distribution, especially suitable for space-constrained locations such as urban streets and residential areas
• Residential communities: as community distribution centers, supplying power nearby to shorten low-voltage lines and reduce line losses
• Industrial and mining enterprises: providing power distribution for small and medium-sized factories, with flexible relocation and expansion capabilities
• New energy projects: photovoltaic power stations and wind farms use compact substations for step-up and grid connection
• Temporary power supply: construction sites, mining oilfields, and other temporary power consumption locations
• Charging stations: providing dedicated power distribution for centralized charging stations