A Consequence of Failure of Mid Span Compression Joint on the Kelanitissa-Kolonnawa Line

Mid-span compression joints in overhead transmission line conductors need to give not only reliability, but also electrical and mechanical properties equivalent to the original conductor. The use of an inappropriate joint can lead to disastrous consequences. An example of this is the complete blackout of the Sri Lankan power system in October 2009 through the use of an inadequate size joint. This paper is based on investigations which revealed that the initiating cause of the blackout, was the failure of a previously replaced inadequate mid-span straight-through joint between ZEBRA and ZTACIR conductors. Inadequate line protection allowed it to progress to a complete blackout. A detailed analysis of the failure is presented and provides information to avoid such occurrences in the future.