Introduction: High contact resistance on switches, fitted with sulphur hexafluoride (SF6) interrupter units, carrying out compensation switching duties in applications where the loads are low.

Objectives: This project aims to carry out research and development into high contact resistance on switches, fitted with sulphur hexafluoride (SF6) interrupter units, carrying out compensation switching duties in applications where the loads are low.

This high resistance has been attributed to the drying out / decomposition of contact lubricants producing a high resistance layer. It has also been suggested, by the manufacturers of the equipment, that due to the nature of the equipment and lubricants used a chemical reaction may also be occurring causing a build up of silver sulphide (Ag2S) on the contact surfaces.

Currently it is suspected that this issue is the cause of the high contact resistance evident on the AEG S1 models of switch. Additional issues have been reported implying this issue may also be occurring on the ABB HPL300 switch carrying out the same compensation duty.