Dynamic state estimation-based protection of power transformers

Power transformers are expensive and critical power system components. Reliable and secure protection schemes for transformers are extremely important. While transformer protection has evolved to a high degree of sophistication they cannot ensure 100% reliable and secure protection. A new transformer protection scheme based on dynamic state estimation is proposed. The dynamic transformer state is continuously estimated from measurements and the protective decision is based on the transformer state only (operating condition or health status). This scheme requires very few and simple settings, such as maximum permissible hot spot temperature. The protection algorithm is object-oriented. Specifically, the transformer model is expressed in a standard format, named the algebraic quadratic companion form (AQCF) and the dynamic state estimation operates directly on this object model. The method has been demonstrated in the laboratory. The paper describes the laboratory hardware. An example transformer protection is presented for a 115/25 kV three-phase transformer. Results verify the advantages of this scheme over traditional methods.