Directional undervoltage pilot scheme for distribution generation networks protection

The trends of the actual distribution networks are moving toward a high penetration of distributed generation and power electronics converters. These technologies modify contribution-to-fault current magnitude and raise concern about new protection systems to accurately detect faults on distribution networks. This paper proposes a directional under-voltage pilot scheme to detect faulted branches in distribution networks. The aim of the proposed scheme is to provide an efficient algorithm with functions for fault detection, fault localization and fault isolation. The fault detection is based on the voltage measurements at each node of the distribution network when a fault occurs, which are compared with the prefault values. Then, once the fault is detected, the proposed scheme locates the fault comparing the current direction at each node. As the direction of the current when a fault occurs is known, the scheme uses this information to locate the faulted branch. After that, a trip signal is sent to the corresponding breakers in order to isolate the branch under fault. Besides, the proposed scheme enables back up protection using communication between adjacents nodes. A distribution network has been modeled in PSCAD/EMTDC software to verify the proposed algorithm, taking into account distributed generation provided by both wind turbines (doubly fed induction generator and permanent magnet generator with full converter) and solar photovoltaic installations. The behavior of the under-voltage measurements and the current direction has been studied for both generation and loads nodes. This algorithm has been tested varying fault location and resistance along the modeled distribution network. (4 pages)