Compact Substation Sizing and Configuration Guide for Overseas Projects

Compact substation sizing starts with load analysis. Calculate the total connected load, apply demand factor and diversity factor, then add a 20-30% margin for future expansion. Common ratings for industrial applications range from 100 kVA to 2500 kVA.

For outdoor compact substations, consider the temperature rise derating. A transformer rated at 1000 kVA at 20°C ambient may need to be derated by 10-15% in tropical climates with 40°C+ ambient temperatures.

The MV side typically uses load-break switch-fuse combination or vacuum circuit breaker depending on the transformer rating and protection requirements. For transformers above 800 kVA, circuit breaker protection is recommended.

The LV side should include main breaker, outgoing feeders, metering compartment, and optional reactive power compensation. Confirm the number of outgoing feeders, breaker ratings, and whether surge protection is required.

Compact substation enclosures are classified by IP rating, material (steel, concrete, composite), and thermal management method (natural ventilation, forced ventilation, or air conditioning).

For corrosive environments (coastal, industrial zones), specify stainless steel or anti-corrosion coating. For high-temperature environments, consider forced ventilation or air conditioning to maintain internal temperature within equipment limits.

IEC 62271-202 defines the requirements for compact substations. Verify that the enclosure design, fire resistance, and internal separation meet the standard's requirements.

Include the site layout, soil conditions, ambient temperature range, altitude, seismic zone, utility interface requirements, and local grid frequency in the RFQ. Also specify whether civil works (foundation, earthing) are included in the supplier scope.

Request the overall dimension drawing, weight, lifting points, cable entry method (top or bottom), and transport feasibility for the destination site access road.