Control cable

Think this requires some additional info. (Hint: a control cable could be either mechanical or electrical). Each would have its own requirement. What's yours?

What are you trying to control?

As load voltage drop and current capacity would not be important cryteria to be considered, another important factor is mechanical strenght when laying the cables.

Normaly, in practice, you may consider:

-2,5 mm2 for current transformers secondaries

-1,5 mm2 for voltage transformers or control cables

Care must be taken when passing these cables parallel to power cables due to longitudinal induction.

The calculation of the mutual inductance may be made according to CCITT tables, as a hand calculation is time consuming.

Care must be taken when paralleling control cables in the field, due to common mode induction. This induction is due to static coupling between the inductor and the induced cables.

In all cases it is recommended to use a cooper shielding strip around the cables, the thickness of which to be calculate by means of capacitive coupling method.

A reccomended practice is to use a cooper clad compensation cable, layed in the upper part of the trenches or in the side of the cable trays.