ANALYSIS OF SYMMETRICAL THREE PHASE SHORT CIRCUITS

In the analysis of symmetrical three-phase short circuits the following assumptions are generally made.

1. Transformers are represented by their leakage reactances. The magnetizing current, and core fusses are neglected. Resistances, shunt admittances are not considered. Star-delta phase shifts are also neglected.

2. Transmission lines are represented by series reactances. Resistances and shunt admittances are neglected.

3. Synchronous machines are represented by constant voltage sources behind sub-transient reactances. Armature resistances, saliency and saturation are neglected.

4. All non-rotating impedance loads are neglected.

5. Induction motors are represented just as synchronous machines with constant voltage source behind a reactance. Smaller motor loads are generally neglected.