Prefabricated Underground Compact Substation

Cotenele is a leading electric equipment manufacturer in China. The YBD series prefabricated underground compact substation manufactured by us entire assembly is mounted below ground to eliminate surface occupancy and blend seamlessly into cityscapes. Drawing on overseas innovations, this compact unit encases transformers, load switches, and fuses in a sealed oil‑filled tank that can operate reliably even during temporary flooding. Adhering to the global trend of developing environmentally friendly power facilities while emphasizing innovation and aesthetics, it complies with the domestic standard GB17467 and the international standard IEC 62271-202:2022. Its versatile design suits residential complexes, industrial zones, roadside verges, municipal projects, mines, oilfields, ports, and tourist attractions, thereby reducing land use, easing urban land‑use conflicts, and serving as a tangible indicator of a city's modern civilisation level.

What is a prefabricated underground compact substation?

The YBD series prefabricated underground substation refers to a substation in which the complete set of compact substation equipment is installed inside a fully sealed enclosure, and the entire unit is placed below ground level. Its internal equipment is the same as that of a ground-mounted compact substation — it steps down the 10 kV input voltage to 400/220 V distribution voltage and then delivers it to the load points.

This fully buried type is also called an underground substation. Its enclosure has excellent corrosion resistance and compressive strength, and is absolutely sealed.

Internal Structure

The YBD series prefabricated underground substation mainly consists of an underground part and an above-ground part:

1. Underground Part: Underground Transformer (including the prefabricated pit)

- A compact power device combining the transformer, medium-voltage load break switch, and fuses.

- Installed in the pit, occupying no ground space.

- The enclosure is made of corrosion-proof stainless steel and is fully sealed.

- Protection rating up to IP68: can operate while briefly submerged.

- Medium and low voltage cables are connected with waterproof, fully insulated, and fully shielded terminations.

2. Above-ground Part: Outdoor MV/LV Switchgear (advertising light-box style)

- A hybrid structure integrating an advertising signboard with outdoor switchgear.

- The inside contains HV and LV switch cabinets, with advertising light boxes on both sides.

- The enclosure is divided into compartments for MV switchgear, transformer, and LV switchgear.

- Each compartment is equipped with lighting and a locking switch.

- Forced ventilation, temperature controls, and heaters are provided.

Product Features

1. High Reliability

- Enclosure made of corrosion‑proof stainless steel, fully sealed, IP68 rating.

- Can operate while briefly submerged, capable of withstanding flooding.

- Flexible MV protection: can use SF₆ gas-insulated ring main units or oil-immersed load switches + fuses for full‑range protection.

- Design service life up to 20 years.

2. Energy Saving

- Prefers low-loss underground transformers: available in S11, S13, SBH15 series etc.

- Compared with S9, no-load losses are reduced by 30%, and load losses by 15%.

3. Noise Reduction

- Transformer installed underground significantly reduces audible noise.

- Almost no impact on nearby residents.

4. Aesthetics and Environmental Harmony

- Occupies little or no ground space.

- Above-ground part can be designed as an advertising light box, blending with surroundings.

- Can be integrated with landscaping to enhance community appearance.

5. High Automation

- Equipped with integrated monitoring devices using GPRS wireless network technology.

- Reports operating status to management staff.

6. Factory Prefabrication

- Fully prefabricated at the factory — short production cycle.

- Low investment and quick returns.

Normal Operating Conditions

Special Operating Conditions

Any conditions other than those listed above shall comply with GB1094.1, GB/T11022, GB/T1404B.1 and GB7251.1.

Technical Parameters

Installation Methods

1. Pit Foundation Construction

- Use steel plate (≥6 mm) pre-formed and fully sealed; or a precast reinforced concrete structure with advanced waterproofing.

- Top ventilation openings must be effectively rainproof and waterproof.

- Side and bottom are treated with special waterproof materials.

2. Equipment Installation

- Underground transformer installed in the prefabricated pit.

- MV/LV cables are connected with waterproof, fully insulated, fully shielded terminations.

- Cable entry/exit holes use the Roxtec waterproof sealing system.

3. Above-ground Installation

- Outdoor MV/LV switchgear installed on the surface.

- Both sides are advertising light-box structures.

- Side doors can be opened fully (180°) and are supported by gas springs.

Installation Diagram

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