Cable Rating

Have you queried the manufacturer/supplier?

6.6 KV line to neutral or earth, 11 KV line to line. [?]

This may help:

http://cr4.globalspec.com/comment/702498

- MS

Specification of cable is always dependent on the type of system earthing adopted. The insulation of cable for unearthed system need to be better than that for the earthed system. The reason being in an unearthed system the line to ground voltage may reach near about the line voltage, whereas in an earthed system the same will be restricted to 1/√3 times of line voltage. Hence 11kV (UE) cable needs better insulation than 11kV (E) cable. Incidentally 11 kV (E) cable can be used for 6.6 kV (UE) system.

As debata7 already said it, according to IEC 60502-2 ch.4.1:

"The rated voltage of the cable for a given application shall be suitable for the operating

conditions in the system in which the cable is used. To facilitate the selection of the cable,

systems are divided into three categories:

- category A: this category comprises those systems in which any phase conductor that

comes in contact with earth or an earth conductor is disconnected from the

system within 1 min;

- category B: this category comprises those systems which, under fault conditions, are

operated for a short time with one phase earthed. This period, according to

IEC 60183, should not exceed 1 h. For cables covered by this standard, a

longer period, not exceeding 8 h on any occasion, can be tolerated. The

total duration of earth faults in any year should not exceed 125 h;

- category C: this category comprises all systems which do not fall into category A or B."

For rated 10/6 kV [12 kV maximum] category A&B 6 kV phase-to-ground rated cable will be enough. In C category [more than 1h operation with one phase grounded]

8.7 kV [phase-to-ground] is recommended[15/8.7 kV cable rated].