Canfuwyd drwy ymchwilio ymhellach bod y nam wedi digwydd am fod y pwyntiau terfynu yn y cebl wedi gorboethi. O ganlyniad, roedd y cerrynt a lifai drwy’r cebl wedi cynyddu, gan chwythu ffiws ac achosi methiant y prif gyflenwad pŵer i’r cyfarpar signalau. Roedd y generadur wrth gefn wedi cychwyn wedyn fel y dylasai, ond bu cylched fer oherwydd y cebl difrodedig, ac arweiniodd hynny at fethiant y generadur wrth gefn. Mae’r math hwn o fethiant yn anarferol dros ben ac nid oedd wedi digwydd o’r blaen.
Subsequent investigations showed that the fault resulted in the termination points in the cable over-heating. As a consequence of this, the amount of current drawn increased which blew a fuse and caused the cessation of the mains power supply to the signalling equipment. As it should, the stand-by generator then started but the damaged cable caused a short circuit which resulted in the failure of the back-up generator. This type of failure is highly unusual and had not been experienced before.