A fault on a branch circuit opens protective devices "D", "C" and "B." The entire power supply to the building is completely shut off. This non-selective operation is normally the result of a medium to high level short circuit. This fault may be line-to-line, line-to-ground, or 3 phase bolted in nature. It is also possible that the non-selective OPENING could be due to overload conditions on the branch circuit.
