Shielded Medium Voltage Cables

Short answer is the tape screen will likely provide a better shield (has fewer gaps compared to a wire screen), but the copper wire screen will provide much better cable short circuit protection (due to its much larger cross sectional area, in the event the cable insulation is damaged by a digger or spade, etc) and cable earthing facilities.

I would go with the wire screen, you should not be running data cabling anywhere near the 20kV cable anyway, and certainly not in the same trench/conduit as the 20kV cable (it's in the wiring standards).

ok thanks but were i can find data to read about the 2 cases wire screen or tape screen ,yousaid wires are good for short circuit but i can see on the sample small wires about 12 around the cable and they can be cut very easely while the cable with tape (5 mil) 20% overlap completly shield the cable please advice

If you compare the cross-sectional area of the copper wires to the copper tape you will find that it is considerably larger, and hence can withstand a much higher short circuit (or fault) current (commonly indicated in kA - thousands of amps). One of the mains reasons for the copper wire screen is safety - in the event you damage the cable, shorting the live conductor to the screen you want the screen to carry the short circuit current long enough to cause the protection to operate and isolate the cable, not melt and blow apart preventing the cable protection from operating and possibly electrocuting someone (as could be the case with the thinner copper tape).

In the end it depends on your application, but most importantly on what your cable's potential short-circuit current is.

For more information have a look at previous threads on CR4 regarding the subject, along with cable manufacturer websites.