Analysis and evaluation of ageing phenomena of high-power LV and HV fuses due to longterm operation

Once inserted as new electrical equipment, inevitable ageing processes can easily sink into oblivion since fuses usually provide their service in an unobtrusive way for decades, provided they are properly dimensioned and operated. The issue of ageing only then become visible when an inexplicably blown fuse has already caused a costly disruption. In contrast, an invisibly aged fuse which fails when demanded also constitutes a severe silent risk. Given a sample of 240 low-voltage HRC fuse-links and about 30 HV fuse-links plus accessory with a minimum age of 35 years and different application histories, various tests were carried out – primarily according to IEC 60269 and IEC 60282 and considering TGL. Special attention was spent to fuse applications in 3-phase AC systems. By means of examining their thermal behavior, time-current characteristic, cyclic stability and their melting and breaking behavior, possible deviations from the expected results, indicated deteriorations. Based on the test results, the identified ageing phenomena within the sample will be described, classified and, in as much as possible, explained through conceivable causes. Finally result, admissible generalizations shall be made on the basis of the test sample, causes for the ageing behavior of LV and HV fuses shall be drawn and further studies shall be suggested.