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Olympic Dam underground mine is located in South Australia approximately 520km north-north-west of Adelaide. The copper-gold-uranium deposit is extracted by open stope mining. The empirical Mathews stability method has been applied to open stope stability forecasting at Olympic Dam for the more than 20 years. This method adjusts the rock tunneling quality index (Q’) to allow for a rock stress factor, the orientation of any discontinuity and the orientation of the geometric surface formed by the excavation. The applicability of the Mathews stability method at Olympic Dam was analysed by assessing the volume of over break outside the stope design profile. It was found that 41% of all stope surface predictions were correct, and that 59% (by difference) of all predictions were therefore incorrect. This was found to be primarily due to the method as applied at Olympic Dam, rather than the inherent errors of the Mathews stability method. However there are a number of weaknesses in the Mathews stability method including the inability to identify structural weaknesses in the rock mass, to allow for different stress concentrations around irregular shaped stopes and to account for stope relaxation. A high resolution non-linear, Hoek Brown, numerical model is capable of providing displacement, velocity and strain rates for points within a rock mass. Velocity is the modelled rate of displacement of the points within the rock mass relative to the stope profile. An existing numerical model of this sort at Olympic Dam was used to investigate the relationship of the velocity of points moving toward a stope, and the probability of them becoming over break. It was found that with increasing rates of velocity the probability of a point becoming over break increased. The identified limitations of the application of the Mathews stability method are not enough to justify removing the method from the stope design process at Olympic Dam. With the implementation of recommended improvements such as, increasing the frequency of window mapping collection, live stress measurements and detailed post-mining assessment of stopes, an increase in the methods reliability can be expected. These improvements should be incorporated in conjunction with the continued trial of velocity as a stope performance indicator at Olympic Dam.

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One of the consequences of competitive electricity markets and international commitments to green energy is the fast development and increase in the amount of distributed generation (DG) in distribution grids. These DGs are resulting in a change in the nature of distribution systems from being "passive", containing only loads, to "active", including loads and DGs. This will affect the dynamic behavior of both transmission and distribution systems. There are many technical aspects and challenges of DGs that have to be properly understood and addressed. One of them is the need for adequate static and dynamic models for DG units, particularly under unbalanced conditions, to perform proper studies of distribution systems with DGs (e.g., microgrids). The primary objective of this thesis is the development and implementation of dynamic and static models of various DG technologies for stability analysis. These models allow studying systems with DGs both in the long- and short-term; thus, differential and algebraic equations of various DGs are formulated and discussed in order to integrate these models into existing power system analysis software tools. The presented and discussed models are generally based on dynamic models of different DGs for stability studies considering the dynamics of the primary governor, generators, and their interfaces and controls. A new comprehensive investigation is also presented of the effects of system unbalance on the stability of distribution grids with DG units based on synchronous generator (SG) and doubly-fed induction generator (DFIG) at different loading levels. Detailed steady-state and dynamic analyses of the system are performed. Based on voltage and angle stability studies, it is demonstrated that load unbalance can significantly affect the distribution system dynamic performance. Novel, simple, and effective control strategies based on an Unbalanced Voltage Stabilizer (UVS) are also proposed to improve the system control and the stability of unbalanced distribution systems with SG- and DFIG-based DGs.