Roedd yr adolygiad cychwynnol yn awgrymu mai ymchwydd pŵer sylweddol oedd achos posibl y methiant. Fodd bynnag, ar ôl i bersonél Western Power ymchwilio ymhellach i’r mater, canfuwyd mai’r hyn a achosodd y digwyddiad oedd methiant cebl oedd yn cysylltu’r generadur ‘wrth gefn’ â’r system signalau yng Nghaerdydd.
An initial review suggested the cause may have been a significant power surge. However, further investigations involving Western Power personnel were able to discount this and by early afternoon it became apparent that the root cause was the failure of a cable connecting the ‘stand-by’ generator to the signalling system at Cardiff.