The combined substation, also known as the American-style box-type substation (or "USP" for short), is a compact, complete set of power distribution equipment. It integrates high-voltage switchgear, distribution transformers, low-voltage switchgear, energy metering devices, and reactive power compensation units into one or several enclosures according to a specific wiring scheme.

It is designed for 10/0.4kV three-phase AC systems to receive and distribute electrical energy.

• 01

  Cores

  Cores are manufactured with precision cut, burr-free, grain-oriented silicon steel. Many grades of core steel are available for optimizing core loss efficiency.

• 02

  Coils

  Pad-mounted transformers feature a rectangular coil configuration with wire-wound, high-voltage primaries and sheet-wound secondaries. Coils are wound using the highest quality winding machines providing exacting tension control and conductor placement for superior short-circuit strength and maximum efficiency.

• 03

  Core and Coil Assemblies

  Pad-mounted transformer core and coil assemblies are braced with heavy steel ends to prevent the rectangular coil from distorting under short-circuit conditions. Plates are clamped in place using presses, and welded or bolted to form a solid core and coil assembly.

• 04

  Tanks

  Transformer tanks are designed for high strength and ease of handling, installation, and maintenance. Tanks are welded using precision-cut, hot rolled, pickled and oiled steel.

Compact Size & Small Footprint

For the same power rating, the volume is only 1/3 to 1/5 that of a European-style substation. For instance, a 315 kVA unit occupies approximately 2–3 m², whereas a European type requires 5–6 m². This makes it ideal for space-limited areas such as urban roadsides and residential compounds.

Lower Initial Cost

With its simplified construction and reduced material usage, the purchase price for the same capacity is typically 30%–40% lower than that of a European-style unit. This makes it highly attractive for cost-sensitive projects (e.g., temporary power supply, rural grid upgrades).

Flexible & Easy Installation

- Fully sealed and maintenance-free (for the high-voltage section); no need for periodic dusting or internal inspections.

- Can be mounted directly against a wall, recessed into a building facade, or installed in underground garages.

- Uses pre-molded cable connectors for quick on-site termination.

High Power Supply Reliability

The dual-fuse combination provides more reliable protection than a single fuse. The backup fuse can interrupt fault currents up to 50 kA or higher, effectively clearing internal transformer faults. Additionally, the multi-circuit LV design allows for branched distribution—failure in one circuit does not affect others.

Strong Overload Capability

Thanks to the relatively large volume of transformer oil (compared to same-size dry-type transformers) and effective heat dissipation (via corrugated tank walls), it permits 20%–30% continuous overload. Suitable for applications with seasonal load fluctuations (e.g., construction sites, temporary exhibitions).

Low Noise Level

The enclosure and oil-immersed construction provide inherent sound insulation. For the same capacity, operating noise is typically 5–10 dB lower than that of a European-style substation, making it suitable for residential neighborhoods.