Transformer Modeling for Electromagnetic Transient Analysis

Transformer modelling for electromagnetic transient analysis encompasses the development of mathematical and topological representations that capture the dynamic response of power transformers to sudden disturbances. Such disturbances include switching surges, fault inception, inrush currents and geomagnetically induced currents. Models range from equivalent-circuit formulations, which represent windings, leakage and magnetising branches, to detailed topological constructs that incorporate core nonlinearities, inter-winding coupling and magnetic hysteresis. Accurate representation of core saturation and zero-sequence paths is vital to predict inrush magnitudes and waveform distortion. Modern approaches leverage laboratory test data combined with finite-element simulations or terminal measurements, reducing reliance on proprietary design details. Implementation in specialised software environments—such as EMTP-type tools, ATPDraw or Simulink—enables comprehensive studies of transient phenomena, informing system protection schemes and mitigating overvoltages. Advances in parameter identification, dynamic inductance matrices and variable-gap modelling have enhanced the fidelity of these models, while maintaining computational efficiency suitable for large-scale network studies. The broad applicability of these advances spans high-voltage transmission systems, renewable integration, converter transformers and power electronics interfaces, underscoring their global significance for resilient and secure energy infrastructure.

Research from Nature Portfolio

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Research from all publishers

Recent studies have advanced topological transformer models by refining core saturation representation. One approach improved a three-legged low-frequency model by distinguishing moderate and deep saturation regimes. By introducing a variable inductance to account for flux-dependent air-gap effects at core joints and carefully distributing zero-sequence impedance among the three phases, the model achieved close agreement with inrush and sequence-current tests on a 50 kVA transformer. This work demonstrates how adaptive parameterisation can bridge the gap between laboratory hysteresis data and field measurements.

Another development proposed a streamlined topological framework for three-phase transformers under deep saturation. By parametrising individual legs and yokes using special-purpose saturation tests combined with typical grain-oriented steel curves, this method obviated the need for hypothetical leakage inductances. The model accurately predicts inrush current events and offers insights into the impact of geomagnetically induced currents, making it particularly valuable for resilience assessments in high-latitude power networks. A complementary comparison of two hysteresis representations, both derived from direct current terminal tests, validated that optimised grey-box models can faithfully reproduce no-load current waveforms, further enhancing ease of parameter identification and practical applicability.

Transformer Modeling for Electromagnetic Transient Analysis publication trend

The graph below shows the total number of articles in transformer modeling for electromagnetic transient analysis across all publications each year (not limited to Nature Index journals).

Technical terms

Electromagnetic transient (EMT): A rapid change in voltages or currents within an electrical network, typically due to switching operations or faults, requiring time-domain analysis.

Topological model: A circuit representation that explicitly maps magnetic and electrical paths, including core branches, leakage flux and winding connections.

Hysteresis: The lagging of magnetic flux density behind the driving magnetic field, producing non-linear and history-dependent core behaviour.

Zero-sequence impedance: The combined impedance encountered by zero-sequence currents flowing equally in all three phases and returning through the neutral.

Core saturation: The condition in which increases in magnetising force yield diminishing increments of flux density, markedly altering transformer reactance and waveform shape.

References

1. Further Improvements in Topological Transformer Model Covering Core Saturation. IEEE Access (2022).
2. Toward a simple topological model of a three-phase transformer including deep saturation conditions. COMPEL The International Journal for Computation and Mathematics in Electrical and Electronic Engineering (2023).
3. Comparing two topology transformer hysteresis models derived from DC hysteresis measurements. COMPEL The International Journal for Computation and Mathematics in Electrical and Electronic Engineering (2023).