The ever increasing demand on the electrical energy has led to the diversification on the electrical energy generation technologies especially from the renewable energy sources like the wind and the solar PV. Micro-grids powered by distributed generators utilizing renewable energy sources are on the increase across the globe due to the natural abundance of the resources, the favorable government policies and the resources being environmentally friendly. However, since the electrical power distribution networks have always been passive networks, the connection of the distributed generations (DGs) into the network has associated several technical implications with distribution network protection and Over-Current Protective Devices (OCPDs) miss-coordination being one of the major issues. The need for a detailed assessment of the impacts of the wind turbine generation (WTGs) on the distribution networks operations has become critical. The penetration of the WTGs into a distribution network has great impacts on the short circuit current levels of the distribution network hence eventually affecting the OCPDs coordination time margins. The factors which contribute to these impacts are: The size of the WTG penetrating the distribution network, the location at which the WTG is connected on to the network and the Type of the WTG interfacing technology used. An important aspect of the WTGs impacts studies is to evaluate their short circuit current contribution into the distribution network under different fault conditions. The magnitudes of these short circuit currents, both the three phase and the single-line-to-ground (SLG) faults, are needed for sizing the various Over-Current Protective Devices (OCPDs) utilized in protecting the distribution network. The sizing of the OCPDs entails among other procedures coordinating them with both the upstream and the downstream OCPDs so that there is sufficient time margin between their Time Current Characteristic (TCC) curves. For Fuse-Fuse protection coordination, the ANSI/NEC rules stipulate that a minimum of 0.025seconds or more time margin should be maintained between the primary/downstream fuse and the secondary/upstream/back-up fuse. Due to the topological and operational differences between the different types of WTGs interfacing technologies, the electrical generators design industry has divided wind turbine generators into four different types labeled as Type I, Type II, Type III and Type IV. This paper presents a detailed study of the impacts brought upon by integrating wind turbine generators on a conventional Fuse-Fuse protection coordination scheme. A conventional Fuse-Fuse protection coordination scheme was modeled in Electrical Transients Analysis Program (ETAP) software and WTG with different interfacing technologies connected. A study of the impacts brought by the integration of the WTGs on Fuse-Fuse Miss-coordination was performed. IEEE 13 Node Radial Distribution Test Feeder was used for the study.
Fault and Short Circuit Analysis for Wind Turbine Generators Grid
