What is used for capacitor protection in low-voltage compensation cabinets?
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I’ve seen many low-voltage compensation cabinets these days use dz47 for protection – does that work well? I’ve seen a paper stating that the short-circuit capability of dz 47 is too low, and it cannot effectively suppress capacitive surge currents. Is that correct?
DZ47 protection is acceptable. Although the short-circuit breaking capacity of dz 47 is low, it is not used to interrupt inrush currents in low-voltage capacitor compensation; rather, it serves as a substitute for fuses. It is mainly to interrupt the short-circuit current.
Since the reliability of these fuses in operation is not very high, we now use DZ47s for protection in all cases. However, given the limited breaking capacity of DZ47s, we have several guidelines to follow. It is not installed in the main substation but in the distribution rooms of each workshop, enabling local compensation. While being converted to DZ47, all the capacitor-specific contactors that were originally used were replaced with series reactors. A main fuse is installed below the knife switch as a backup protection for the DZ47. This is because there is concern that DZ47 may fail to operate due to a short circuit. For the selection of DZ47, the motor protection type is used, rather than the circuit type. This post was last edited by lihy on 2009-4-16 22:32]