What’s new in cable?

By A Falconer, Aberdare

 

Published in:

Electricity+Control February 2014 (pages 4 – 6)

Enquiries: afalconer@aberdare.co.za

 

The full article on What's new in cable? can be downloaded in PDF format.

 

Looking at all the options on offer and at the conflicting requirements, it is possible to see that cables are anything but simple. Cables must be able to work routinely at temperatures that the human hand cannot tolerate and be able to handle mind-boggling currents, albeit for a short time, without damage.

They must often ensure the current stays in the conductor, when massively persuasive forces are trying to get it to do otherwise. Cables can be fixed or flexible, and they can be seen as resistors, inductors, capacitors or even wave guides.

Insulated cables

Once the Ingula pumped storage station is in operation, cables with a rated voltage of 400 kV will be used in South Africa. The next big step for cables will be 800 kV, but there is not much information on such cables in the public domain at this stage. The most advanced cable in terms of fire performance is what is referred to as a fire survival cable. Fire survival cable does not survive fires, but fire survival cable can maintain emergency electricity supplies after regular cables have failed.

As an alternative for MV XLPE cable, a specially developed polypropylene insulation is being explored – this will mean a simpler manufacturing process, lower manufacturing energy costs and material that can be recycled.
Unique mark cables are being considered as a solution to cable theft in South Africa.

Overhead conductors

Some suppliers are replacing the steel core in ACSR conductors with a composite fibre core. Finally, the concept of high temperature superconductors is still in development and the feeders installed are therefore experimental and closely monitored. The advantage of high temperature superconductors is that they can handle huge currents without loss. This means that high temperature superconductors can convey large amounts of power without the need for the high voltages usually associated with such power.

 

Take note:

  • Cables are anything but simple.
  • Fire survival cable does not survive fires, but can maintain emergency electricity supplies after regular cables have failed.
  • The advantage of high temperature superconductors is that they can handle huge currents without loss.

Captions if needed
Photo 2: An accelerated ageing facility for testing MV XLPE cable.
Photo 3: A fire performance test facility, with a flame propagation chamber on the left and a smoke emission chamber on the right.
Photo 5: A typical HTS cable. The three concentric conductor layers are barely visible, yet each can handle almost 2 000 A