The following table shows the number of unplanned outages of the GB electricity transmission system which led to customer disconnection between 1991-92 and 2007-08. The table also shows the amount of power in megawatt hours (MWh) lost in each of those years. The data are taken from National Grid's annual transmission performance reports.
Total MWh lost Total number of events 1991-92 407 33 1992-93 1,210 52 1993-94 1,051 19 1994-95 518 34 1995-96 311 23 1996-97 215 33 1997-98 614 28 1998-99 859 33 1999-2000 587 23 2000-01 1,404 20 2001-02 699 29 2002-03 415 26 2003-04 1,329 27 2004-05 1,119 28 2005-06 1,939 28 2006-07 511 25 2007-08 1,675 49