When setting more than two main transformers, select each capacity according to the power failure of one main transformer. Residual capacity can guarantee at least 60-75% of the primary load or the total load of the substation. Usually 75% primary substation and 60% secondary substation are used. The force rate of the primary side of the oil-immersed transformer is related to the load rate. When the load rate is less than 60%, the force rate of the primary side is 11%-18% lower than that of the secondary side. High load rate is beneficial to improve the force rate of high pressure side. Because the load rate is high (expensive), the capacity of the interceptor is large and the investment is increased.
The capacity of an oil-soaked transformer in a low-voltage 0.4 kV substation should not exceed 1600 kV. The capacity of electrical equipment is large, the load is concentrated, and the oil-immersed transformer with capacity above 2000 kVA can be selected under the condition of reasonable driving. In recent years, some manufacturers have produced large capacity ME, AH low-voltage circuit breakers and current-limiting low-voltage circuit breakers. Civil buildings in 1250 kVA and 1600 kVA oil immersion transformers are many, especially 1250 kVA. Therefore, the recommended capacity of a single oil-immersed transformer is less than 1250kVA.
The capacity of oil-immersed transformer must be selected according to the calculated load. To determine the capacity of the oil-immersed transformer, the load rate of the oil-immersed transformer must be determined first. When the air vibration loss is equal to the square of the load rate and load loss, the efficiency of oil-immersed transformer is higher. The load rate at the high efficiency point of the oil-immersed transformer is between 63% and 67%. The load rate of oil-immersed transformer supplied with fixed load is usually about 85%. However, this is not comprehensive from the point of view of saving electricity. At the same time, the various economic costs of driving oil-immersed transformers are also worth considering. Including fixed assets investment, annual operating costs, depreciation costs, taxes, insurance and so on. Selection of oil-immersed transformer capacity, appropriately improve the load rate of oil-immersed transformer, reduce the number or capacity of oil-immersed transformer, that is, sacrifice operating efficiency, reduce one-time investment, yes choice.
Post time: Nov-03-2021
