147Transients on Overhead Lines
For analyzing a very fast front surge (switching surge in a gas-insulated
bus) or a lightning surge, stray capacitances of a CB between poles and the
ground have to be considered.
2.2.2.3 Transformer
As explained in Section 2.2.2.1.1, a transformer is represented by its leakage
inductance for most switching surge analyses. When dealing with a fault
surge, especially in a low voltage system with a transformer of high resis-
tance grounding or an isolated neutral, the transformer winding, either the
Y or Δ connection, has to be taken into account. Occasionally, the magnetiz-
ing impedance of the iron core has to be considered.
For a lightning surge analysis, stray capacitances between the primary and
secondary wi