Transformer models in EMTP/ATP

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Saturable Transformer Model • Uses a star-circuit representation • User could include saturation data • Good for single-phase transformers • Should not be used for 3-phase high reluctance transformers (if no delta winding present) • The model requires the following data: The voltage rating of each winding (winding!) The leakage impedance of each winding The transformer connectivity information BCTRAN • Admittance matrix model • Represents a linear relationship between the primary and secondary voltages and currents • [R] and [ωL] -1 must be separated • BCTRAN supporting routine generates 3-phase coupled R-L {Type 1,2,3,... .PCH file} • Data Required MVA rating Nominal L-L voltage (terminal and not! winding) Winding connections Short circuit impedances, losses No-load current and loss
Magnetizing core modeling • Must be considered in the following studies • Transformer energization studies • Load rejection studies • Switching of transformer terminated lines • Ferroresonance studies • CT saturation • CCVT modeling • No-load losses include: • Eddy current loss and • Hysteresis loss • Could be represented with a resistance Rm in parallel with the nonlinear magnetizing inductance, or • As external, nonlinear (hysteretic) inductance connected to a low voltage winding Hybrid model - XFMR • The user can construct the transformer model on three sources of data: – Design parameter: specify geometry and material parameters of the core and windings. – Test report: standard transformer tests. – Typical values: typical values based on the voltage and power ratings. • The model includes: – an inverse inductance matrix for the leakage description, – frequency dependent winding resistance, – capacitive coupling, – and a topologically correct core model with individual saturation and losses in legs and yokes. 10 / 19 11/6/2012
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Transformer models in EMTP/ATP

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