With the global increase in the number and the capacity of the distributed generators (DGs) penetration levels in the power systems networks’, there is need for a detailed assessment of the impacts the DGs have on the power systems operations. The distribution network topology, control and protection philosophies are all designed to extract power from the transmission network and distribute it to the loads. The distribution network is not designed to have generators directly connected into it hence its power flow is unidirectional from the main utility grid to the loads. During a short circuit, the presence of DGs in a distribution network creates an increase in the short circuit current levels of the distribution network and a bi-directional power flow.

A wind turbine generator (WTGs) is one of the most commonly utilized form of renewable energy largely integrated into the distribution networks. 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 IEEE 13 node radial test feeder was modelled for the short circuit study in electrical transient analysis program (ETAP) software. The short circuit study was then performed on the radial test feeder firstly without WTGs connected and secondly with different WTG interfacing models connected at various nodes on the 13 node radial test feeder. Four models utilizing either the induction machines or the synchronous machines were simulated in ETAP for the WTG interfacing. The four models were classified as Type I, Type II, Type III and Type IV WTGs.

Placement of the four models of the WTGs, Type I, Type II, Type III and Type IV WTGs created an increase in both the three phase and the SLG short circuit fault currents levels of the test feeder. Of the four models the Type I, Type II and Type III WTGs displayed similar characteristics in the increase in both the three phase and the SLG fault currents levels hence the three models were represented as one WTG model and referenced as a doubly fed induction generator (DFIG) machine. The Type IV WTG model was the only unique machine in how it impacted on the fault currents hence it was studied alone. The two WTG models, that is the DFIG machine and the Type IV machine, were then broadly classified as the two main interfacing technologies utilized in the WTG modelling from either the induction machines or the synchronous machines. This paper presents a detailed investigation on the impacts the two WTG interfacing technologies, the DFIG and the Type IV WTG models with their capacities being varied from 1MW to 3MW have on both the three phase fault currents and the SLG fault currents occurring at selected nodes of the IEEE 13 node radial test feeder chosen for the study.