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The work involved the replacement of an existing, outdated substation within a restricted space, without disrupting the existing services. There were two main incoming lines, for normal and alternate feeders, that required secondary distribution panels and metering panels at 416/240V and 208/120V.
A loop style MiniSub was employed alongwith a separate radial SF6 switch to provide the two service feeders that were key interlocked as per the Utility’s operating practices. To minimise the space requirements, the MiniSub had dual secondary windings feeding main breaker, PUC and distribution panels outputs at the two voltages of 480 and 208V.
Along with the savings in space, the use of a dual secondary winding eliminated the need for a second transformer and switchgear to transform the 416 V to the 208V distribution load – as well as reducing the 416V transformer overall load requirement ( the double transformation of the 208 V load) – thus reducing transformer load losses. Similarly as the MiniSub was pre-assembled the labour and material costs of installing separate switchgear, transformers and distribution panels was greatly reduced.