semiconductive layer

Increasing the 'effective' conductor diameter and therefore reducing the corona losses as well as the insulation requirements.

That is why a 440kVolt supply cable consists of 4 conductors with a spacer every 50 metres or so... It makes the conductor behave as if it was the diameter of the 4 wires spacing i.e. 5 inch diameter as opposed to a ½" cable, this reduces enormously the voltage stress on the dielectric (air in this case) and reduces the losses due to corona discharge...

The same is true for the EHT lead carbon layer...

John.

This is the fact.

Why so?---You will need to get additional coaching on:

• Lines of Force
• Conformal Transformation
• Electric Field
• Magnetic Field
• Maxwell,Lorenze----- Laws of Electro-magnetics

John

That's interesting - what is the reason for using a semiconducting layer rather than a conducting tube around a cheap core? I can imagine cable flexibility and cost coming into this; on the other hand, I suppose the cooling would be better for the conductive tube.

Fyz

Right. Here is how it was explained to me for a standard high voltage cable with a screen. The inner semi conductive layer (wrapped around the conductor) prevents build up of excessive electrical field strength at the individual wires of the flexible conductor and the insulation. The outer semiconductor layer (in contact with the screen) serves as core shield and performs for protection against the electric shock, avoidance of partial discharges in the conductor assembly, generation of the radial electrical field in the insulation and discharge of current in the event of fault.
As I found out, a standard high voltage power cable with only a semiconductor layer and no earthed metal screen is NOT touch safe (because of the reasons mentioned above), and you certainly would not want to touch it.