(105c) Then the Lights Flickered

Just after 2pm, the lights flickered across South East Queensland. The electricity network in the region had been destabilised following the catastrophic failure of the Callide C4 power unit turbine. As the control system failed, the turbine started free spinning backwards and importing electricity rather than exporting to the network, before it catastrophically disintegrated.

This presentation will explore the process safety failings that led to the tripping of C4. This includes a look at the management of change process to change out the battery and battery charges for the control systems, as well as design related issues that triggered the uncontrolled shutdown of both the AC and DC systems. Because of how the fault occurred, it prevented the system being shut down. As the event unfolded, the control room lost all sources of information, making diagnosis of the fault challenging. C4 was the third battery charger to be replaced in an upgrade project, with the two prior charger replacements taking place uneventfully.

A subsequent investigation uncovered several failings in the major hazard management and process safety management system of the company involved. These lessons can be applied across a range of incidents.