NH
Low Voltage Fuses European NH Knife Blade Fuse System
General User's demand for maximum service reliability in low voltage networks coupled with effective and economic operation places considerable requirements on the quality of protective gear used in the electrical networks. SIBA's continuous advances in development and quality of their LV fuse links are preferred for use in feeder line protection. When SIBA LV fuse links are suitably selected to match the line characteristics, they provide the maximum protection against all faults that are generally encountered. The fuse current rating range is capable of protecting small over currents up to its rated breaking current. Design SIBA fuse links are built to the highest standards, this is met by utilizing the highest quality materials, the most highly automated construction techniques and a work force that has an ongoing training program for maintaining and improving the quality of its products. The fuse link is constructed utilizing a high quality ceramic for the main body with the fuse elements directly spot welded to the contacts of the knife blades. For most fuse links, a dual indicating system is incorporated, the standard flap type that is on the faceplate and the other that is on the top and center of the ceramic body for a more direct viewing. Technical Data and Explanations Current Limiting The thermal and dynamical capacity of electrical switchgear components are determined by the peak value of the prospective short circuit current Is. The magnitude of this peak short circuit current Is a value that is dependent on the rams value of prospective short circuit current I p and the phase angle of fault occurrence that induces a DC offset. Due to current limiting, high short circuit fault currents do not rise up to their peak capability, when SIBA LV fuse links of the corresponding rated current are utilized The current limiting diagram shows the function of the prospective short circuit current Is depending on the prospective current I p (sym.r.m.s.). The coherence between the prospective current I p (sym.r.m.s.) and the efficiency of current limitation (cut off current ID) by SIBA LV fuse links is given by the more flat running lines for the various fuse rated currents. Time-Current Characteristics The time-current characteristics for LV fuse links type gG are represented as "medium characteristics curves", these are within the cutoff range stipulated by VDE 0636-2. Maximum deviation in the current coordinates is ± 7 % . Fuse Discrimination The discrimination between two fuse links of different current ratings can only be determined when considering the service voltage. The distance of discrimination in radially operated systems of 1:1.6, referred to the fuse link rated current as well as the use of fuse links of the same rated current in meshed networks is only applicable at service voltages of 1.1xUn/ .
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