Types of Short Circuit Faults
The most common type of short circuit in a three phase system is a single conductor to earth fault (Fig 1. Phase-to-earth). This is when one of the conductors in a circuit comes into contact with an earth.
The next most common type of short circuit is a phase to phase or conductor to conductor fault (Fig 2. Phase-phase) – when two of the conductors in a circuit come into contact with each other.
Next is a double phase or double conductor to earth fault (Fig 3. Phase-phase-to-earth) – two of the two conductors in a circuit each simultaneously come into contact with an earth.
And lastly, the least common type of short circuit is a balanced three phase or three conductor fault (Fig 4. Three-phase) – when all three conductors come into contact with an earth. Whilst this is uncommon, it can happen, and design engineers must go to considerable lengths to guard against the consequences of such an event.
In all cases these faults are short circuits – the path of least resistance is through a fault, and not through the equipment you are attempting to power.