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.

1. 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.

2. 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).

3. 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.

4. 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.

5. 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).

6. 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.