Lmax - Maximum Cable Length equation for TNS Vs IT system

For small cables, you can forget the reactance term. There is however a potential problem with IT systems used for personal protection (for example operating theatres etc) and that is very long cables potentially present a capacitance to Earth risk from contact with a conductor and an Earth. This needs to be a lot of cable to be realistic in practice, but the designer needs to be aware of it. The voltage drop is your cable design criterion, with the Earth loop impedance usually a limitation before volt drop steps in but would not apply to IT systems. Allowable volt drop is fairly flexible, as is the consideration of maximum versus likely loading. The design job is not necessarily simple! Why the question might have an interesting answer, or are you a student? 

For small cables, you can forget the reactance term. There is however a potential problem with IT systems used for personal protection (for example operating theatres etc) and that is very long cables potentially present a capacitance to Earth risk from contact with a conductor and an Earth. This needs to be a lot of cable to be realistic in practice, but the designer needs to be aware of it. The voltage drop is your cable design criterion, with the Earth loop impedance usually a limitation before volt drop steps in but would not apply to IT systems. Allowable volt drop is fairly flexible, as is the consideration of maximum versus likely loading. The design job is not necessarily simple! Why the question might have an interesting answer, or are you a student?