A new model for short-circuit current calculation of distribution networks integrated with numerous distributed generations

With raising penetration of distributed generations (DGs), it is of great demand for accurate short-circuit current calculation which is the foundation of planning, operation and relay protection of power systems. When distribution networks are integrated with increasingly number of DGs, short-circuit current calculation becomes less convenient because the dimension of nodal admittance Y matrix expands a lot. This paper proposes a new model for short-circuit current calculation with a large amount DGs. Effects of those DGs on short-circuit current are modeled by a standard second-order linear ordinary homogeneous difference equation. With the proposed model, the nodal admittance Y matrix doesn´t increase correspondingly when the amount of DGs increases. Thus, the proposed model saves a lot both in memory storage space and computing resource. Simulations are carried out in the IEEE distribution 33-bus system. Results demonstrate that the proposed model has equal accuracy as traditional method, and much higher efficiency in both memory storage and computing time cost.