Graphical coordination program aids system relaying at Consumers Power

Consumers Power Company, an investor-owned, combination (gas and electric) utility serving customers throughout most of Michigan´s lower peninsula, is in the process of adding a 345/138 kV autotransformer bank, rated 300 MVA self-cooled, to one of its substations. Before a system modification of this scale can be completed, protective relay settings throughout the area must be reviewed. Consumers Power Company´s experience using the coordination graphics module to review settings for the planned system change and determine new settings to provide the required coordination is reported. The coordination analysis of overcurrent and distance devices is described.<>