200.2[(A)] grounded insulation

[fmtjfw]

Anybody know why 200.2[(A)] requires the grounded conductor to be insulated for the circuit voltage for 0--1000V, but only 600V for 1001V and over? Is there something special about 601--1000V?

 

[jcormack]

Most higher voltage power conductors have an over all-shield (braid or tape) within the cable that is grounded, no real need for higher voltage insulation on the ground wire