High-speed transfer of two 4 KV motor bus sources using a digital motor bus transfer system

At many industrial facilities, distribution busses serving critical loads are supplied from two power sources. Typically, this bus arrangement is in a main-tie-main arrangement. Upon the loss of the normal power source, critical motor loads must be transferred to the alternate source without damaging the equipment, and ideally, without interrupting the process. In this application, two digital motor bus transfer systems were installed to transfer two 4 KV busses to two sources. This paper describes the steps to applying a digital motor bus transfer system to medium-voltage switchgear at a large chemical company including the feasibility analysis, available transfer methods, input/output considerations, settings, and commissioning methods. A summary of actual operations data to date and lessons learned is also included.