Behind every electric vehicle
charging station, every industrial park, and every commercial complex lies a critical but often overlooked infrastructure layer: the power distribution system. This is the network of switchgear, transformers, distribution cabinets, and substations that receives electricity from the utility grid and routes it safely to end-use equipment. When a B2B procurement team evaluates a charging plaza project, the charging piles typically receive the most attention — but it is the Sennan Electric
High Voltage Switchgear and Sennan Electric
Low Voltage Distribution Cabinet that determine whether the site operates reliably, safely, and cost-effectively for years to come.
Chongqing Sennan Electric Co., Ltd. is one of the few Chinese manufacturers that produces both EV charging equipment and complete power distribution systems. This dual capability gives the company a systems-level perspective on electrical infrastructure design — ensuring that the distribution equipment is properly matched to the charging loads it serves. The company's Sennan Electric prefabricated substation solutions integrate high-voltage switchgear, transformers, and low-voltage distribution into a single weatherproof enclosure, simplifying installation and reducing site engineering requirements.
A commercial EV charging plaza is, from an electrical engineering perspective, a concentrated load center that demands significant power from the grid. A site with four 120kW DC fast chargers draws up to 480kW — requiring a 10kV high-voltage connection, a step-down transformer, and low-voltage distribution equipment to route power to each charging station.
Understanding this chain is essential for procurement teams, because every link must be correctly specified, manufactured, and tested to ensure reliable site operation.
The company's high-voltage switchgear is designed for indoor installation in electrical rooms or within prefabricated substations. The product line covers voltage ratings from 10kV to 35kV, with current ratings from 630A to 3150A.
Circuit Breaker Technology: The switchgear uses vacuum circuit breakers (VCB) for applications up to 35kV. Vacuum breakers offer several advantages over SF6 alternatives: no greenhouse gas concerns, lower maintenance requirements, faster operating speed (35–60ms interruption time), and longer service life (10,000+ operations). For specific applications requiring SF6 insulation, the company offers SF6 load break switches with environmentally responsible gas handling.
Protection Relay: Modern digital protection relays provide overcurrent protection (50/51), earth fault protection (50N/51N), overvoltage (59), undervoltage (27), and circuit breaker failure protection (50BF). The relay includes communication interfaces (IEC 61850, Modbus RTU) for integration with supervisory control and data acquisition (SCADA) systems.
| Parameter | Specification |
| Rated voltage | 12kV / 24kV / 40.5kV |
| Short-circuit breaking current | 25kA / 31.5kA / 40kA |
| Protection class | IP4X (enclosure), IP2X (compartment) |
Low-Voltage Distribution Cabinet: Design and Specifications
The Sennan Electric low voltage distribution cabinet is the workhorse of the low-voltage side, receiving 400V three-phase power from the transformer and distributing it to outgoing loads. The company's design follows a modular philosophy — allowing customization of the number and rating of outgoing circuits, the inclusion of power factor correction capacitors, surge protection devices, and energy metering.
Key design features include:
Modular Structure: The cabinet uses standardized modular components — main incoming breaker, busbar system, outgoing breakers, and auxiliary modules — arranged in a Type-tested assembly (TTA) configuration. This modular approach allows the cabinet to be customized for each project's specific circuit requirements while maintaining standardized manufacturing processes.
Busbar System: Copper busbars are sized for the rated current and short-circuit withstand, with tin plating for corrosion resistance. The busbar arrangement follows a phase-segregated design with adequate creepage and clearance distances, minimizing the risk of phase-to-phase faults.
Breaker Selection: The cabinet accommodates molded case circuit breakers (MCCB) for outgoing circuits and air circuit breakers (ACB) for the main incoming breaker. Breaker ratings range from 16A to 3200A, with electronic trip units providing adjustable long-time, short-time, and instantaneous protection settings.
Power Factor Correction: Integrated capacitor banks with automatic power factor correction controllers maintain the power factor above 0.95, reducing utility reactive power charges and improving system efficiency.
Surge Protection: Type 1 or Type 2 surge protective devices (SPD) are installed at the incoming section, protecting downstream equipment from lightning-induced and switching surges.
Energy Metering: The cabinet can include digital energy meters with communication interfaces (Modbus RTU, RS485) for remote energy monitoring and sub-metering of individual outgoing circuits.
Key specifications:
| Parameter | Specification |
| Rated voltage | 400V AC, three-phase |
| Rated current | Up to 4000A (main busbar) |
| Short-circuit withstand | 65kA / 1s (main busbar) |
Prefabricated Substation: Complete Integration
For sites where building a dedicated electrical room is impractical or costly, Sennan Electric prefabricated substation solutions offer a turnkey approach — integrating high-voltage switchgear, transformer, and low-voltage distribution cabinet into a single weatherproof enclosure that can be installed outdoors.
The prefabricated substation, also known as a box-type substation, is manufactured with a steel enclosure treated for outdoor installation — featuring corrosion-resistant coating, ventilation louvers with filters, and internal temperature management. The enclosure is divided into three compartments:
High-Voltage Compartment: Houses the high-voltage switchgear (load break switch with fuses or vacuum circuit breaker), voltage and current transformers, and surge protection. Access is through a door with interlocks that prevent opening when the equipment is energized.
Transformer Compartment: Contains the step-down transformer (typically dry-type for indoor applications or oil-immersed for outdoor installations). The compartment includes ventilation openings and temperature monitoring sensors. For dry-type transformers, the compartment provides adequate clearance for natural air cooling, while oil-immersed transformers include oil containment provisions.
Key advantages of prefabricated substations include:
- Reduced site engineering: No need to build a dedicated electrical room — the substation arrives fully assembled and tested
- Faster installation: Site work is limited to foundation preparation, cable connection, and commissioning
- Weatherproof: IP54 enclosure rating protects equipment from dust, rain, and humidity
- Compact footprint: Designed to minimize land area requirements, critical for urban installations
- Relocatable: The substation can be moved if the site is relocated, protecting the equipment investment
Safety and Protection Features
Power distribution equipment operates at voltages and currents that pose significant safety risks. The company's products incorporate multiple layers of protection:
Arc Fault Protection: Internal arc classification (IAC) ensures that if an internal arc fault occurs, the arc energy is contained within the switchgear, protecting personnel in the vicinity. The company's switchgear is tested to IAC AFL at 31.5kA for 1 second.
Quality Assurance and Certifications
As with the company's charging products, the power distribution equipment undergoes rigorous quality control throughout the manufacturing process. The company holds 15+ qualification certificates covering product safety, electromagnetic compatibility, and environmental management.
All switchgear and distribution cabinets are type-tested according to IEC and GB standards, with test reports covering dielectric strength, short-circuit withstand, temperature rise, internal arc, and mechanical operation. These test reports are available to B2B clients as part of the technical documentation package.
Why Choose Sennan Electric for Power Distribution?
The decision to source power distribution equipment from a manufacturer that also produces EV charging stations provides several distinct advantages:
System-Level Optimization: The company understands the load characteristics of its charging equipment — inrush currents, harmonic content, duty cycles — and designs the distribution equipment to accommodate these characteristics optimally.
Single-Source Accountability: When a site experiences an issue, the operator contacts one manufacturer rather than navigating between a switchgear supplier, a transformer supplier, and a charging station supplier. This simplifies troubleshooting and warranty management.
