Why is our domestic power supply 240v?

It all started with a couple of guys you may have heard of – Thomas Edison and George Westinghouse, way back in the 1880′s. (incredibly – the companies they founded still exist in some form today, as General Electric and Westinghouse)

The processes that led to the final decision on voltages and currents also included development of the Electric Chair, as a means of a more “humane” execution.  In fact, that’s where the term “Electrocution” comes from.

In the 1880’s Edison had developed his electric lighting using direct current, which also soon turned out to be the right sort of current for the electric motors and other industrial equipment of the day.

While it worked well, transmission was difficult – the power eroded over only a few miles, meaning there had to be plenty of sub-power generators placed throughout the cities.  For this reason, Edison had difficulty in winning bids to put electric lighting into cities and towns with very low density suburbs.  He had more success in closely packed cities.

Edison’s power was direct current at 110 volts. While it could give quite a jolt, it was not considered lethal.  In fact, most electrical engineers of the day had accidentally zapped themselves on more than one occasion.  110 volts was also used as the carbon filaments used by Edison in his light bulbs would burn out too quickly at a higher voltage.

Edison’s direct current power was always delivered by a cable buried underground.  Despite the 110v not being lethal in short bursts, Edison felt for safety reasons, all electrical cables should be below ground.

Meanwhile, a nearly rival, George Westinghouse, was developing alternating current.  This was much more effective to transmit over long distances and Westinghouse began to make real inroads into the domestic and commercial markets.

However, AC current was very dangerous.  As demand for power grew, Westinghouse and similar providers of AC current ignored the potential dangers and instead of burying the cables underground, they criss-crossed cities such as New York City (picture below, 1890) with literally thousands of live, unshielded wires that led to many deaths.

Edison, feeling that AC power was too dangerous and hence not suitable for domestic use, started to lobby the US Government about the dangers.   One of his more pointed actions was to publicly lobby that AC power could be used to provide a quicker, more humane execution for condemned criminals.

(Secretly, in doing so, he had hoped to raise the issue of the dangers of AC current to the public)

Westinghouse opposed, but eventually Edison’s suggestion was adopted and AC power (using Westinghouse generators) was used to develop the first working Electric Chair, and the first execution by the same device.

So why do we now have alternating current?

Despite Edison’s efforts, in the end, AC power won out, only due to the fact that it could be transmitted more efficiently, and in time new developments in electric motors and other equipment allowed the use of AC power.

What led to Australia using 220-240v?

In the US, it’s 110-120 volts, as that was the voltage that Edison used to develop the carbon filament light bulb.

However, soon after this, in Europe, the development of metal filament lamps was underway, which could withstand higher voltages (and provide more efficient lighting, and more cost effective electricity transmission) than the US 110v system.

In the USA, the standard had already been established, so they stayed with 110-120v and in Europe (and most of the rest of the world) 220-240v was adopted – and those standards are still in place today, over 100 years later.

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