Application of superimposed voltage in the detection of faults in resonant distribution systems

As a high percentage of the length of overhead lines corresponds to distribution lines, there is a strong probability that faults in overhead distribution lines will occur. When a fault occurs in a resonant grounded system, the short circuit current is below the threshold of the protection system. This means that the sensitivity of the protection system is not good enough to detect the fault and as a consequence the fault cannot be isolated. In this situation, the contact of a high voltage conductor with ground is a hazard to people. This is especially dangerous in the distribution lines as they are close to final customers. For this reason, it is fundamental to have at the power system´s disposal devices that permit the detection of that type of faults. This work presents the definition of a new methodology for the detection of fault currents in resonant grounded systems based on superimposed voltage.