Optimization of MV distribution system designs

This paper will present new approach that is advantageous to medium voltage (MV) distribution design configurations for large industrial and power distribution system configurations (specifically Main-Tie-Main) for large industrial and power station installations. Sixty years of traditional low cost design approaches (typical MTM and operated with open tiebreaker) are re-evaluated to demonstrate that traditional low capital cost design may miss improvement opportunities. Those opportunities can be: major capital expenditure (CAPEX) reduction; power quality improvement; MV motor soft starter deletion; improved system stability to name a few. Many designers may not have considered the component interrelationships and/or their tradeoffs when in an integrated system. The designer and/or user should consider the advantages of higher short circuit capacity (SCC) systems by integrating fault current limiters (FCL) and MV switchgear. Utilizing higher SCC systems permits the power system designer optimization opportunities not possible before using conventional design methods. This paper will provide documentation of substantial savings of capital investment and energy under higher SCC conditions. The savings in one system component will offset another's increased cost. An obvious benefit of stiffer systems is ease of direct-online starting (DOL) of large motor driven compressor trains. The future need for motor soft starters minimizing system impact will be challenged. This paper may change fundamental system design methodology for system designers by removing several performance tradeoffs.