基于磁路特征的三相三柱式变压器励磁参数识别

Identification Method for Excitation Inductances of Three-phase Three-limb Transformer Based on Characteristics of Magnetic Circuit

针对励磁参数在变压器保护中的应用,提出了三相三柱式变压器励磁电感参数的识别方法。根据三相三柱式变压的磁路特征建立了反映主磁通感应压降与励磁电流关系的简化数学模型。对于Y/Y接线的变压器,在求得其主磁通感应压降后,根据所建模型可稳定、准确地求取其在非内部故障情况下的励磁参数,所求参数与内部故障相比特征明确。Δ侧环流不是三相三柱式变压器的励磁电流,在用绕组端电压代替主磁通感应压降后,可直接应用于Y/Δ接线变压器,励磁涌流时仍可准确计算其励磁参数,其特征明确,可与差动保护配合,构建励磁涌流识别判据。通过统一电磁等效电路(unified magnetic equivalent circuit,UMEC)仿真模型验证了该方法的正确性。

For the application of excitation parameters in transformer protection, the inductance identification method of three-phase three-limb transformer was proposed. Based on the characteristic of magnetic circuit, a mathematic model which links the voltages induced by the main fluxes and the currents of the windings was established. For transformers with Y/Y connection, using main flux induced voltage, the excitation inductances can be calculated accurately and steadily under conditions of normal operation, inrush current and external faults, and the characteristics are distinct from internal faults. The delta side circulating current is no part of excitation currents of three-phase three-limb transformers, so with main flux induced voltage replaced with winding voltage, the proposed method can be applied to transformers with Y/A connection directly. In this case, the excitation inductances can be calculated under inrush condition, and can be taken as identification criterion for inrush current in differential protection of the transformer. The proposed method is validated by unified magnetic equivalent circuit （UMEC） transformer model.