Basic elements of the protection plan
Protection Plan for Medium Voltage Public Distribution Networks

The appearance of a fault on a network will cause variations in its characteristic electrical quantities, and even in certain other associated physical quantities. By monitoring and analyzing these quantities, protection systems are able to detect the presence of a fault and take action.

Polyphase faults will generate a very significant increase in phase currents, making them relatively easy to detect. Ground faults are characterized by a "leakage" of current to ground, which can be detected by one of three methods:

• residual current monitoring (i.e. the sum of the three phase currents), well suited to large systems such as MV feeders;

• detection of...