SA severe lightning risk area — specialist

South African Weather Service lightning specialist says SA has one of the highest rates of lightning strikes per square kilometre in the world.

SA WAS a severe lightning risk area and had one of the highest rates of lightning strikes per square kilometre in the world, South African Weather Service lightning specialist Karel de Waal said yesterday.

Lightning-related deaths in SA account for 1,5 to 8,8 per million of the population, according to an article in the South African Journal of Science, entitled The Lightning Climatology of SA.

This is more than 15 times the global average.

Parts of SA’s central and northern interior fall into the extreme risk category, with the highest risk being the windward side of the Northern Drakensberg, the article says. It also notes that almost all of the insurance-related inquiries received by the Weather Service are related to lightning.

Eskom is one of the main users of data from the Weather Service’s lightning detection network, which indicates an area’s lightning risk profile.

Eskom spent millions of rand each year replacing infrastructure damaged by lightning, the utility said yesterday.

"Each lightning (strike) transfers an enormous amount of energy onto the Eskom power system in a very short time. This means any weakness in (insulation) … caused by damage, pollution or poor design or installation … is exploited and exposed," research, test and development acting GM Barry MacColl said.

"Damage may occur during a lightning event, but the actual failure comes some time later … losses of our large power transformers run into tens of millions of rand per transformer.

"In our medium voltage networks, distributing power directly to consumers, the replacement costs approach R100m per annum," he said.

However, there were hardwired solutions — such as earthing and surge arresters — to minimise the damage, as well as the risk information received real-time from the Weather Service.

Mr de Waal said mines, and other infrastructure-heavy industries, also received lightning information through the lightning detection network’s web portal.

The network, initially deployed in 2005, has 24 sensors strategically located around SA.

- BusinessDay