14.9 LV HRC Fuse Time Current Curve Tool.
Figure 14.29 LV HRC TCC Calculator
The time current tool provides generic clearance curves for the DIN NH and BS88 industrial fuses to the standard IEC 60269. The calculator produces a time current curve characteristic plot for up to two curves. The data entry and output is detailed as follows.
TCC 1 Amp Rating (NH DIN Fuse)
A drop-down list menu gives a range of choices between 32 amperes and 1250 amperes for NH DIN Fuses.
TCC 2 Amp Rating (BS 88 fuse)
A drop-down list menu gives a range of choices between 32 amperes and 1250 amperes for BS 88 Fuses.
This will display both TCC 1 (NH DIN Fuse) and TCC 2 (BS88 Fuse) fuse time current curves. Either one can be deselected by clicking on the associated colour block at the top of the graph.
Enter Specific Input Time
By entering a specific input time ranging from 0.01 to 10 seconds, a corresponding clearance current for the associated fuse will be given. (This value will be displayed in amperes)
Enter Specific Input Current
By entering a specific input current in amperes (guidance ranges will be displayed depending on the selected fuse amps, a corresponding clearance time for the associated fuse will be given.
A mistake that is often seen is the use of pre-arcing curves with no allowance for tolerance or clearance. This calculator factors this into the curves and is based upon generic curves as displayed in Amtech for BS 88 fuses. The DIN fuses are based upon the ABB DIN-type HRC-fuse links, <1250 ampere gG -types from the 2018 Protection & Connection Fuse Gear catalogue. Allowance for clearance has been take from the ABB “Curves” software.
14.10 Risk Assessment Forms
Within this online suite of guides, the results of the calculations can be printed off. There is an option to create dynamic risk assessment forms in line with the four P principles. The following is an example of one such risk assessment form which is provided for the IEEE 1584 calculator.
Figure 14.34 Risk Assessment Form