Cable Data for I.S. Verification Calculation

[sysengineer]

I'm in a bit of a dilemma with a intrinsically safe circuit validation cert.

Where either or both the effective total inductance and capacitance is not greater than 1% of Lo and Co respectively then the permitted inductance or capacitance of the interconnected cable is determined by subtracting these effective values from the Co and Lo of the source of power.

The use of the Lo/Ro ratio as a cable parameter is permitted, provided that the effective total capacitance is greater than or equal to 1% of Co. If the effective total inductance is greater than 1% of Lo then the permitted L/R ratio of the cable must be recalculated in accordance with IEC 60079-25. Where the use of the Lo/Ro ratio is permitted, then if the cable has an L/R ratio less than, or equal to the permitted value, it is not necessary to satisfy the Lo requirement.

In my circuit, the effective total capacitance is greater than 1% Co. However effective total inductance is less than 1% Lo. Does this mean I can calculate my max. cable parameters by subtracting from Co and Lo as described in the first statement? I'm confused with the either or both.

Also, in my case Lo/Ro is not defined from the manufacturer so regardless of the fact that the effective total capacitance is GREATER than 1% of Co AND the effective total inductance is LESS than 1% Lo as in the second statement - I cannot verify my cable by comparing the L/R ratio. Presumably then I must make sure that the cable inductance is less than the value obtained by subtracting the effective total inductance from Lo. This introduces another problem because I do not have inductance/m of the cable. The cable manufacturer only specifies an L/R ratio! (note the cable is BS 5308 Part 1 Type 1).

In this case can I use the resistance/km and multiply by the L/R ratio to obtain inductance/km and use this to verify my circuit inductance?

I hope all of this makes sense.
Dan