It would seem with second calculator the original the Zs was not calculated but just a figure entered as a start point with the
modified version of calculator I have added a calculation to give Zs.
In accordance with what I said earlier, think that the revised format is much more useful. One can now enter Ze (or PSCC at CU, as you have now done it), cable details and circuit length and get calculated figures for max circuit VD and Zs (and PSCC). It’s no longer possible to calculate max circuit length from other inputs, but I never really saw much practical point in that, anyway.
You have added a note indicating that the inputted Ze figure is “No longer used for anything” but, as the calculator currently is, that is not true. The inputted Ze is currently a crucial part of the calculation of the circuit Zs. You
need to input Ze (or, if you prefer, PEFR at CU - what some call Zdb)
Now that it is an ‘output’ (only), Zs would probably be best moved to the bottom, with the other ‘outputs’ - and, similarly, ‘cable length’ (now only an input) should probably be ‘moved up’. More generally, I would be inclined to put all the inputs first, then the outputs. Some of the displayed figures do not seem very useful (e.g. ‘Impedance of Live Conductors’, ‘mV/A/m’ figures etc.), and could perhaps be removed.
As I wrote last night, for a TN installation, I don’t really see any point in having “PSCC at circuit end” as an output. What you
do need as an output is Zs (or PEFC) ‘at circuit end’ - and, as I said, if that satisfies the disconnection time requirements (either in terms of Zs or PEFC) for the circuit’s protective device, then so, inevitably, also will the PSCC. However, it’s probably worth retaining that facility just for TT installations, where Zs requirements will not usually be satisfied (but the PSCC ones still need to be). As for confirming that the PSCC is below the 6 kA, 10 kA or whatever limit of the device, PSCC will obviously be at it’s maximum at the CU, and you don’t need to calculate that, since it is one of the figures you have to input.
The ‘tabulated CCCs’ displayed for a radial circuit appear to be those for Method 100 - it should probably say so. I’m not sure how you have calculated the ‘tabulated CCCs’ in the case of radial circuits, and I wonder if it wouldn’t be best to suppress that output, to avoid confusing people? In fact, you could simply display the ‘tabulated CCC of (one instance of) the cable in use’ - i.e. as per the current figures for radials.
AFAICS, it appears that you, EFLI and I are all using slightly different methods of arriving at conductor resistivities at 70°C, which leads to us all getting slightly different answers (for Zs etc.). I’m not sure which is the most appropriate/correct, but it might be worth looking into that.
As mentioned last night, you probably should point out that the ‘design current’ being asked for is
not Ib in the case of a ring - but, rather, a VD-specific ‘effective design current’. If you wanted to get more clever, you could ask about the circuit’s OPD and then work it out for itself. You probably should point out (if you retain them) that the displayed ‘mV/A/m’ figures relate to the live conductors, not CPC.
For radials, you appear to be calculating VD on the basis of all the (‘design current’) load being at the far end. As I wrote yesterday, is that correct (i.e. no ‘convention’ about load spreading, as per rings)? Do I take it that the intended ‘design current’ for a radial is the In of the OPD?
Hope some of that might be helpful. If I think of more, I’ll let you know.
Kind Regards, John