Classification Of Substations

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1 1. General Classification of Substations

2 2. Term Definitions in National Standard GB50053-94

4 Example Analysis: Rural Pole-mounted Substation

1. General Classification of Substations

This part divides substations from four core dimensions, covering their functional positioning, management mode, structural form, and geographical location.

Classification Basis	Specific Types & Brief Explanation
Function	– Step-up Substation: Mainly used in power plants to boost low-voltage electricity generated by generators to high-voltage for long-distance transmission. – Step-down Substation: Reduces high-voltage electricity from the grid to medium/low voltage for user consumption (the most common type in urban and rural power supply). – Hub Substation: Located at the intersection of power grids, undertaking power exchange and distribution between multiple grid segments. – Terminal Substation: The last-stage substation in the power supply chain, directly supplying power to end users without further voltage transformation.
Management Style	– Manned Substation: Equipped with on-site operation and maintenance personnel for 24-hour monitoring and management, mostly used in large-scale or key hub substations. – Unattended Substation: Realizes remote monitoring and control through intelligent systems, without on-site personnel, widely used in medium and small-scale distribution substations.
Indoor/Outdoor Structure	– Outdoor Substation: Most primary equipment (transformers, switches) is installed outdoors, suitable for areas with sufficient space and mild environments. – Indoor Substation: All or most equipment is placed in indoor buildings, suitable for dense urban areas, harsh climates (cold, humid), or places with high safety requirements.
Geographical Conditions	– Above-ground Substation: Built on the ground surface, the most common form. – Underground Substation: Built underground (such as basements of buildings), mainly used in urban central areas with tight land resources.

2. Term Definitions in National Standard GB50053-94

This standard focuses on the definition of 10kV and below substations, mainly classified by the installation location and environment of the transformer, and clarifies the attributes of different substation types and supporting facilities.

Core Definition of 10kV and Below Substations

Substation: A facility where “10kV and below AC power sources are transformed by power transformers to supply power to electrical equipment”—this is the basic scope defined by the standard.

Classification by Transformer Installation Location & Environment

Open-air Substation: The transformer is placed directly on the open ground, with no shelter above.
Semi-outdoor Substation: The transformer is still on the open ground, but there is a roof or overhang above it for sun and rain protection.
Attached Substation: One or more walls of the substation are shared with the walls of adjacent buildings; the doors and ventilation windows of the transformer room must open to the outside of the building (not connected to the building interior).
Substation in the Workshop: Located inside the industrial workshop, with the transformer room door opening into the workshop (for direct power supply to workshop equipment).
Independent Substation: An independent building that is not attached to any other structure.
Indoor Substation: A general term for attached substations, independent substations, and substations in workshops (all have enclosed indoor spaces for transformers).

Related Supporting Facilities

Oil Storage Tank: A facility designed to store oil (such as transformer oil); its structure ensures that the oil inside will not be ignited by external burning substances after flowing in.
Oil Retaining Facilities: Facilities used to prevent burning oil (e.g., during transformer oil leakage and fire) from spilling and spreading, reducing fire hazards.

3. Other National Standard Terms

Beyond GB50053-94, there are national definitions for other common substation types:

Terminal Substation: A separately constructed substation at the front end of electricity users. The electricity it outputs can be directly supplied to user equipment without further transformation, usually referring to the last-stage substation that steps down 10kV to 380V (civilian low voltage).
Pole-mounted Substation: An outdoor substation installed on one or more electric poles, with small volume and simple installation, suitable for rural or small-scale power supply scenarios.
Pre-installed Substation (Box-type Substation): A complete set of equipment pre-assembled and type-tested in the factory, usually integrating high-voltage distribution devices, transformers, and low-voltage distribution devices into one or several boxes. It is also called “box change” for short, featuring quick installation and flexible layout.

Example Analysis: Rural Pole-mounted Substation

As mentioned, the small substations built with two poles in rural areas have multiple attribute overlaps:

It is an open-air substation (transformer on open ground) and a pole-mounted substation (installed on poles).
It is also a terminal substation (steps down 10kV to 380V/220V and directly supplies power to rural residents without further transformation).