The operating conditions for outdoor prefabricated substations stipulate an altitude not exceeding 1000m, an ambient temperature range of -25°C to +40°C, a daily average relative humidity not exceeding 95%, and a monthly average not exceeding 90%. Furthermore, the installation site must be kept clear of fire sources, explosive hazards, conductive dust, chemically corrosive gases, and severe vibrations.
Its functional features include a "three-in-one" integrated design comprising high-voltage switchgear, transformers, and low-voltage switchgear. The system offers comprehensive high- and low-voltage protection, ensures safe and reliable operation, and requires minimal maintenance. It boasts a compact footprint, low investment cost, short production cycle, and ease of relocation. The enclosure utilizes a double-layer (composite panel) structure to facilitate thermal insulation, heat dissipation, ventilation, aesthetic appeal, and high-level environmental protection. A variety of enclosure materials are available, including stainless steel, aluminum alloy, cold-rolled steel, and color-coated steel. The high-voltage ring main unit can be equipped with a Feeder Terminal Unit (FTU) and features "four-remote" capabilities (telemetry, telecontrol, telesignaling, and teleadjustment) to enable reliable detection of short circuits and single-phase ground faults.
Regarding key configurations, the high-voltage side typically employs a load switch-fuse combination for protection; should a fuse in one phase blow, a three-phase trip mechanism is triggered. The load switch is available in various types-including compressed air, vacuum, and SF6 gas-and can be fitted with an electric operating mechanism. For transformers with a capacity exceeding 800kVA, a vacuum circuit breaker option is available for protection. On the low-voltage side, the main incoming switch utilizes a universal or intelligent circuit breaker to ensure selective protection, while the outgoing feeder switches employ new-generation molded-case circuit breakers. Additionally, the system can be configured with an intelligent, automatic reactive power compensation device, offering a choice between contactor-based and contactless switching methods.
Other critical parameters include rated capacity (typically measured in kVA or MVA), rated voltage (e.g., 10kV/0.4kV), short-circuit impedance, connection group (e.g., Y/Yno, D/Yno, etc.), insulation class, cooling method (e.g., natural cooling, air-forced cooling, or water cooling), and ingress protection (IP) rating (e.g., IP54, IP65, etc.).
