Simulation and verification of thermal modelling to prevent from damages caused by the use of HH fuses

Abstract

Summary Several cases were reported, where high‐voltage high performance (HH) fuses exploded and damaged the surrounding switchgear. The root causes for these destructions were broken fuse elements damaged by cyclic thermal‐mechanical stress. The question arose how it will be possible to detect broken fuse elements while HH fuses are in operation at high voltage level. The access to the degrading HH fuse is especially not given in switchgear because of the presence of high voltage. An indicator for degrading fuses is the surface temperature. It is also of interest to know the actual temperature of the fuse elements itself to estimate the internal rate of rise of the temperature. This knowledge is important because at a certain temperature level the danger exists that the ceramic fuse body will break unexpected by an explosion. Simulations and measurements were performed to get to know, how and if it would be possible to simulate the temperature distribution as a function for the number of broken fuse elements. With the knowledge of the thermal model of HH fuses it is possible to predict the maximum temperature as well as the possibility to monitor the degradation level of HH fuses.

Simulation and verification of thermal modelling to prevent from damages caused by the use of HH fuses

“…For the detection of high rate of rise of the temperature due to broken fuse elements a temperature monitoring system based on an energy harvesting temperature measurement sensor was developed and patented. [7][8][9][10][11] F I G U R E 3 Switchgear with HH fuse and TOC sensor adapted Figure 7 shows the location of the thermocouple to measure the temperature distribution inside a gas insulated switchgear while the HH fuse has a single broken fuse element at phase b. Due to the broken fuse element the temperature increases rapidly inside the fuse tube whereas in the other fuse tube only a slight increasing of the temperature due to the normal heating can be detected.…”