Abstract:Based on the equivalent circuit diagram of transformer,a new electromagnetic transient simulation model for three - phase three - winding transformer is proposed which could simulate the characteristics of transformation ratio,connection symbol, internal fault and interphase coupling and so on,and a detailed derivation formula of transformer model is given which considers the characteristics of transformation ratio and connection symbol. The proposed model is accurate and reliable,and satisfied with the actual needs of engineering and research comparing with PSCAD.