2. Electrodynamic forces due to short-circuit currents

2.1 Short-circuit current

Contact between points with different potentials is called a short circuit. In the case of three-phase electrical power transmission networks, three types of short-circuit can occur.

• In three-phase short circuits, all three phases are simultaneously in contact. This is the case, for example, when a branch falls onto the line and lies on all three conductors. This fault generates repulsive forces between the two outer phases of the circuit.

• During two-phase short circuits (or two-phase-earth short circuits if the current flows through the earth), only two phases are in contact. This is the case when a branch falls on two conductors, or when an insulating...