ELECTRICAL FAULT LEVEL REDUCTION AT FARLEIGH MILL

THIS PAPER discusses the implications of electrical plant growth within established sugar mills and the resulting adverse impact on the safety of operating and maintenance personnel. This case study follows the amalgamation of a number of Mackay Sugar Mills to form the Mackay Sugar Co-operative Association Ltd. With the rationalisation of the mills, plant from closed factories was relocated to the other mills. As part of this process the 5 MW alternator from Cattle Creek Sugar Mill was installed at Farleigh Mill. This increased the site-based generation from 8 MW to 13 MW, which is a 62.5% increase in capacity. As was discovered about 10 years later, this increased the electrical fault level above the equipment rating for some of the existing installed electrical plant, including the 3.3 kV switchgear. Over the last 10 years we have been through several processes, including fault studies, risk assessments, implementation of temporary control measures, design of a system to fix the situation, and the capital works to fix the problem. Following the capital works we have reassessed some of the switchboards that were highlighted as requiring replacement and the new analysis has shown that there is no longer a need to replace these switchboards as the fault levels are now back within acceptable limits. The whole process identifies the need to preform plant fault studies prior to implementing any major electrical plant expansions.