Transformers

Transformers are the most important components of transmission and distribution systems. For transformers the geometrical data is only available to the manufacturers and it is considered proprietary. Accurate modeling is very important when the transient is dominated by the transformer behavior. Parameters to be specified in transformer models can be obtained from laboratory tests. Basically, International Electrotechnical Commission and Institute of Electrical and Electronics Engineers standards establish tests that are useful for determining parameters of some low-frequency transformer models. Transformer losses may be classified as no-load loss, load loss, and total loss. There are two basic methodologies to determine transformer parameters for low-frequency transients. These methodologies include experimental determination through laboratory tests and through topological information and design data, from electromagnetic field simulations; for example, using finite elements. Saturation can be incorporated into a power transformer model using test data/manufacturer’s curves or estimating the key parameters from transformer geometry.