A new differential protection method for distribution networks with DGs based on adaptive braking zone

The distribution network with large-scale DGs (distributed generations) brings new challenges to traditional protection schemes, which makes it less adaptable for the single-end based protection. Affected by the large-scale distributed generations, the single-ended based protection of distribution network faces the problem of insufficient adaptability. The uncertainty of DG output and the variety of DG locations make the setting calculation of conventional current protection extremely difficult. As a comparison, the application of differential protection to ADNs (active distribution networks) can reduce the impact of DG uncertainty and network complexity better. However, considering the structure changes and weak communication conditions with larger time delays of ADN, it is difficult to balance the sensitivity of differential protection and its ability to resist synchronization error. In order to solve the problem, the new adaptive differential protection method is proposed, which is based on the traditional standard product brake differential protection criterion, making full use of fault current amplitude and phase characteristics. The braking capability adaptively of the new differential protection changes with the current amplitude ratio, so that the protection has high sensitivity and resistance to synchronization errors. Simulations show the effectiveness of the proposed protection method.