At what kVA rating do transformers typically have four bushings?

Transformers typically have four bushings at a rating above 100 kVA because this configuration is necessary to accommodate the electrical connections needed for higher voltage distributions. Having four bushings allows for a more robust electrical connection and enhanced insulation, which is vital for transformers dealing with significant power loads. The two bushing configuration is often used for lower-rated transformers (generally below 100 kVA), as the demands on insulation and connection are not as critical. Therefore, as the kVA rating increases, the complexity of the transformer design also increases, leading to the standardization of four bushings for transformers rated above 100 kVA to ensure operational safety and efficiency.