Thierry Latchimy

Experimental study of HBC fuses working at short and medium pre-arcing times

Pre-arcing stage is the first working step in high breaking capacity (HBC) fuse operation and affects the following step, namely, the arcing step. We have performed realistic HBC fuse tests for short ( 10 ms) pre-arcing times by varying the phase angle of the electrical fault (defined as the phase angle of the fault current once the supplied voltage is applied to the fuse) in the range from 0° to 160°, for two values of the power factor (cos φ ∼ 0.9 and cos φ ∼ 0.1). Experimental values of the pre-arcing time and the arcing time (t are ) are given for t prearc /t MC ? 1 to ∼4.2, and discussed from the energetic point of view by taking into account the inductive source term. The adiabatic assumption classically used in the modelling is also examined. The influence of the pre-arcing step on the arcing step is analysed by means of the Joule integral, the energy dissipated in the fuse and the mass and length of the fulgurite.

Measurement of the pre-arcing time and the fulgurite length in hbc fuse in the case of tests performed with an A.C. 100 KVA station

This study deals with a specific test device especially designed to perform tests on HBC fuse on a scale of a non industrial laboratory. In fact it is not possible for most of academic laboratories to build up a device supplying the same current and voltage ranges as in an industrial test station. Moreover the capacitor bank discharges are often used in academic laboratories to test electric fuses. But the main drawback of the capacitor bank is to supply a non 50 Hz-sinusoidal current waveform for one half period only. We present the first measurements performed on experimental HBC fuses using a 100 kVA station built up from a single phase transformer. These first measurements are performed using various fuse elements with the same geometries as in industrial fuses of the middle voltage range. The filling material is silica sand or quartz sand and it is chosen with the same properties as in industrial fuses. The fuse working is studied experimentally on the whole duration of the fuse working which depends on the values chosen for the power factor and the closing angle. The results are given for the pre-arcing time and the fulgurite length. The power factor put in the tests is equal to cos phi~ 0.9 and cos phi ~0.1, and the closing angle is increased from 0 deg to 180 deg. The results are discussed by taking into account the influence of the energy to dissipate, namely the Joule energy and the inductive energy.