The wonder of electricity

“And it’s thanks to this remarkable natural wonder that you are able to read and understand this article at all: right now millions of tiny electrical impulses are being transmitted between the cells in your brain, enabling you to make sense of what you’re reading.

“Also, if you live in a summer-rainfall area of South Africa – such as Gauteng or the Free State – you will be aware that during winter the air is drier than in summer and often you will get a small shock when touching particular objects like the television set. That is static electricity; like I said, it’s all around you,” explains Eskom spokesperson Khulu Phasiwe.

Electricity is everywhere

All matter – even you – is made up of atoms. Most of an atom is empty space between its nucleus – which is made up of particles called protons and neutrons – and particles that spin around the nucleus, called electrons. Electrons have a negative charge and protons a positive charge. Being oppositely charged, protons and electrons attract each other – the force that holds atomic particles together.

(When you get zapped while touching the television set in your home or reaching for the doorknob, the static you’re experiencing is exactly this – electrons jumping from a negatively-charged object to a positively-charged one.)

In a nutshell, this is what electricity is about and how it works. So how do we make or “generate” electricity – in big enough quantities to make it useful for us to open our electric garage doors, switch on lights, cook food, watch television and heat up water to shower?

What happens inside a power station?

Eskom generates about 90% of all the electricity produced in South Africa. It generates this electricity at power stations, most of which are located near the source of the material we mostly use to generate electricity – coal, water or wind. (Eskom also generates nuclear power – at the Koeberg power station near Cape Town – and is increasingly looking to wind, hydroelectric and solar power).

In essence what happens inside an Eskom power station is that huge magnets are turned inside vast coils of insulated metal wire. The lines of force between the north and south poles of the magnet are cut by the wires in the coil, producing the electric current in the coil itself. The magnet is called the rotor and the coil the stator.

The energy needed to turn the magnets is supplied by coal which is used to heat water. In boilers water is converted into steam – extremely hot steam at temperatures of over 500°C. This steam is then carefully released under great pressure to drive a large turbine which is connected to the rotating magnets. And that process generates electricity.

Eskom’s power stations are enormous structures that employ hundreds of people each. They need to be big because South Africa’s millions of people and its businesses and industries consume massive amounts of electricity every day.

Getting the power to your plug

You will, of course, have seen the big power lines that carry electrical distribution wires over large distances, from the power station to, eventually, your home. For electricity to be transmitted safely and efficiently, it must be sent at a high voltage (pressure) and in a low current. This is because if the current is too high, the cable would heat up too much and even melt. On the other hand, if the voltage is too low, hardly any energy would be carried to your home.

The generators in the power plants produce electricity at 20 000 volts. This voltage is raised or transformed before it is sent out at 132 000, 275 000, 400 000 or even 765 000 volts onto the transmission grid, depending on how far it has to be transmitted.

 

“Of course this voltage is too much for your home to handle so the voltage is lowered, at a substation, to 11 000 volts to be distributed within a particular local area. By the time it gets to your home the electricity you use has been transformed down to 240 volts – what your refrigerator, microwave oven, television set and kettle can manage.

“It’s a remarkable journey – from a piece of coal that boils water that creates the steam that generates the very high-voltage electricity that is then “diluted” to the low-voltage that you and your family rely on every day,” concludes Eskom spokesperson Khulu Phasiwe