Simulated Calculation and Measured Analysis on the Spot with the 750 kV Transformer Switch-In with Load

Through an example of a main transformer switch-in with load during the reverse transmission of a 750 kV power plan, the paper introduces the basic principle of transformer switch-in with load. EMTPE program that is used to establish a calculation model, at the same time mainly considers the excitation characteristics of the transformer, the transient model of the circuit breaker, and the model of high voltage transformer, and calculated the inrush current with transformer switch-in with load in this plan. During system debugging in the plan, the two sets of main transformers passed the closing and opening test, and the data of inrush current in the test are recorded and analyzed. The simulation calculation and measured data show that the results are consistent. The simulation calculation also shows that it is not recommended to perform on-load closing of the transformer except for special circumstances, because of the influence of hysteresis characteristic when the transformer was switched in with load or the terminal voltage of the transformer resumed normal level from a low one after an external near-end fault was cleared, which various transformer differential protection using the characteristics of inrush to implement block scheme may mal-operate.