Utility experiences on busbar faults in a transmission grid

This paper describes some of Statnett`s experiences with busbar faults in the Norwegian power grid. The busbar faults for the 15-year period from 1998 to 2012 in the Norwegian power grid for voltage levels 300 kV and 420 kV are analysed and discussed. A busbar fault in a 420kV substation with double busbar, causing a disturbance with severe consequences, is described in the paper. It is described how the fault started, how the protection should have worked and what happened during this fault. The review of historic incidents of busbars faults (chapter 3), reveal that busbar faults are quite seldom, but often related to a failure in the protection system functionality. Also; when a protection function fails, it is very rarely due to a malfunction in the actual protection device. The busbar fault described in chapter 4 gives valuable learning for operation of busbars and bays, and routines during construction work. As a response to unfortunate malfunctions during the incident, a new procedure for ensuring terminal blocks to be closed after testing was introduced.