Key Points for Selecting Oil-Immersed Transformers
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Load Characteristics
1 .When there is a large number of primary or secondary loads, two or more transformers should be installed. When any one of these transformers is disconnected, the capacity of the remaining transformers shall meet the power consumption of the primary and secondary loads. Primary and secondary loads should be centralized as much as possible and should not be too dispersed.
2.When the seasonal load capacity is large, a dedicated transformer should be installed, such as for air conditioning chiller loads, electric heating loads for heating, etc. in large civil buildings.
3.When a centralized load is large, a dedicated transformer should be installed, such as for large heating equipment, large X-ray machines, electric arc furnaces, etc.
4.When the lighting load is large, or when sharing a transformer between power and lighting significantly affects lighting quality and lamp life, a dedicated transformer for lighting may be installed. In general, power and lighting should share a transformer.
Operating Environment
Under normal medium conditions, oil-immersed transformers or dry-type transformers may be selected, such as in industrial and mining enterprises, agricultural outdoor or attached substations, residential district outdoor substations, etc. Available transformer options include S11, S13, S20, SC(B)10, SC(B)14, etc.
Temperature Environment
① Maintain long-term stability at a temperature of 220°C.
② Withstand short-term operation at a temperature of 350°C.
③ Maintain stable performance across a wide range of temperatures and humidity levels.
④ Will not melt, flow, or support combustion at a temperature of 250°C.
⑤ Will not release toxic or corrosive gases at a temperature of 750°C.
Electrical Load
1) The capacity of the distribution transformer should be determined by synthesizing the installed capacity of various electrical equipment to calculate the calculated load (fire protection loads are generally not considered). The apparent power after compensation serves as the basis for selecting the transformer capacity and quantity. Generally, the transformer load rate is around 85%. This method is relatively simple and can be used for capacity estimation.
2) GB/T17468-1998 "Guide for the Selection of Power Transformers" recommends that the capacity selection of distribution transformers be determined based on the calculated load and in accordance with GB/T15164-94 "Loading Guide for Oil-Immersed Power Transformers" or GB/T17211-1998 "Loading Guide for Dry-Type Power Transformers". The aforementioned two guides provide computer programs and normal cyclic load diagrams for determining distribution transformer capacity.
