Product Definition
Distribution transformers are critical components in the power supply and distribution systems of industrial/mining enterprises and civil buildings. They step down network voltages of 10(6) kV or 35 kV to the 230/400 V busbar voltage used by consumers. These products are suitable for 50 (60) Hz AC systems, with a maximum three-phase rated capacity of 2500 kVA (maximum single-phase rated capacity of 833 kVA; single-phase transformers are generally not recommended).
1) When there is a significant amount of Class I or Class II load, it is advisable to install two or more transformers; the capacity of the remaining transformers should be sufficient to supply the Class I and Class II loads if any single transformer is disconnected. Class I and Class II loads should be concentrated as much as possible rather than widely dispersed.
2) When seasonal loads are substantial, dedicated transformers should be installed-for example, for air-conditioning chiller loads or electric heating loads in large civil buildings.
3) When concentrated loads are large, dedicated transformers should be installed-for example, for large heating equipment, large X-ray machines, or electric arc furnaces.
4) A dedicated lighting transformer may be installed if the lighting load is heavy, or if sharing a transformer between power and lighting significantly compromises lighting quality or bulb lifespan. Under normal circumstances, however, power and lighting share the same transformer.
Transformer Selection Based on Operating Environment
1) Under normal environmental conditions, oil-immersed or dry-type transformers may be selected-suitable for standalone or attached substations in industrial/mining enterprises and agricultural areas, or standalone substations in residential complexes. Available models include S8, S9, S10, SC(B)9, SC(B)10, etc.
2) Inside multi-story or high-rise buildings, non-combustible or flame-retardant transformers should be selected-such as SC(B)9, SC(B)10, SCZ(B)9, SCZ(B)10, etc.
3) In locations where dust or corrosive gases significantly compromise the safe operation of the transformer, enclosed or sealed-type transformers (such as BS9, S9, S10, SH12-M, etc.) should be selected.
4) High- and low-voltage power distribution equipment containing no combustible oil and non-oil-immersed distribution transformers may be installed in the same room; in such cases, the transformer must be equipped with an IP2X protective enclosure to ensure safety.
Selecting Transformers Based on Electrical Load
1) To determine the capacity of a distribution transformer, the installed capacities of various electrical loads should be aggregated to calculate the design load (generally excluding fire-fighting loads); the compensated apparent power serves as the basis for selecting the transformer capacity and the number of units. Typically, the transformer load factor is around 85%. This method is relatively simple and suitable for capacity estimation.
2) GB/T 17468-1998, *Guide for Selection of Power Transformers*, recommends determining distribution transformer capacity based on the calculated load and the criteria in GB/T 17211-1998, *Guide for Loading Dry-Type Power Transformers*. These two standards provide computer programs and normal cyclic load curves for determining distribution transformer capacity.
IInstallation Essentials
Distribution transformers are critical components of substations. Dry-type transformers without enclosures are installed directly on the floor and surrounded by protective barriers, whereas those with enclosures are installed directly on the floor. For installation details, refer to the national architectural standard design atlas 03D201-4: *Layout of 10/0.4 kV Transformer Rooms and Installation of Common Substation Equipment and Components*.
