Black start studies are typically performed as part of system restoration plan when an isolated section of the grid completely shuts down and there are no neighboring systems to assist with the energization. In these cases, pre-selected units with the ability to start themselves with a well established energization plan are used to restart the system. As a case study, a power system comprising of 27 diesel generators, a 130km 230kV transmission line and a mine load is considered in terms of a black start analysis. The system is operated in isolated mode (i.e. not connected to the grid) and the black start ability is critical for energization of the system. The studies placed a strong emphasis on two main transformers at the generating substation since the inrush current imposed by these transformers was deemed to be the determining criteria for a successful black start. Detailed modeling of the transformers was performed to capture the non-linear behavior of the transformer core based on the data provided by the transformer vendor.
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