499. The lead sheath and the armour of a polyphase cable shall be:(1) electrically interconnected throughout their length;
(2) electrically connected at both ends of the cable and to non-current-carrying parts of the electrical equipment or machines to which they are connected;
(3) grounded to the ground network by a connection having an electrical conductivity that is at least that of the metallic armour;
(4) protected against corrosion, if they are exposed to it.