I have never believed that voltage surges or current surges existed.
Electricity, as far as I know, does not move in waves, like the sea. At very high voltages, you do get voltage spikes and transients but these are normally smoothed out at lower voltages. Thus, till now, if people told me that their computer failed due to a voltage surge, I would just smile and say, oh really. Till now.
However, during the recent set of government-sponsored power supply interruptions, I have changed my mind. Sort of. My colleague and friend Alwyn Möller, who is an advocate of the Cape Bar Council and thus a fairly reliable witness, told me that the switchboard on his floor had failed after a recent load-shedding episode. An isolated incident, except the same thing happened to one of our computers and to computers elsewhere, all in load-shedding incidents. Interrupting power to a switchboard or a computer or something else is just that – it happens each time you turn it off. But, with computers, it is not actually just the flipping of a switch – you click the ‘shutdown’ icon and wait and, after a time, it switches off.
When the mains power goes, it is like it switched off at the wall. Our computer that failed was not on a uninterrupted power supply (UPS) – which filters out voltage spikes – and neither was the advocate’s switchboard. However, other computers, not on UPS, did not fail. The fact is that, if these computers failed due to simple voltage spikes (as may happen with lightning) then, since voltage spikes at one point will be present at all other points, all computers should fail. Well, perhaps not, given other factors.
Discussing this topic with others, I found that, in fact, a number of people were reporting ‘load-shedding-related’ equipment failures. I think I know what is happening. Most appliances can take a 10% overvoltage for up to an hour (that is, ~ 250 V single phase for one hour) or even longer. Some will take 500 V for a minute or two, but all will fail almost instantaneously at about 1 000 V.
When you switch off at the wall, there is the simple interruption of current to a load, which is purely resistance – electrically, the current flow is like that of a light bulb. When you switch off the current to, for example, a TV set, there is the requirement that the stored energy in the TV has to go somewhere – this is why, with older TV sets, the screens used to creak when switched off.
Now, get this: if you cut off the power to a whole city, there is stored electrical energy in the system which has to be dissipated. In a large power system, there are plenty of ways in which this energy is dissipated. But when you get to domestic suburbs, the energy has no real place to quickly dissipate except through lights and appliances that are not switched off at the wall. Then, in the domestic suburbs, when the power is switched on again, all that stored energy has to be resupplied and may, particularly in suburbs that have underground cable supplies, cause a system resonance with voltage spikes.
This is a theory, anyway. But the point is, if the theory is correct (and the more mathematical of you are welcome to email me and ask for details) then, surely, consumers have a legal case against the power supply authorities. They do hold themselves indemnified against loss during normal power system operation.
But is this normal? Did we consumers sign up for load-shedding-induced equipment failures? We could sue and could win. Just look at Clause 25 of the Electricity Regulation Act: 25 Liability of Licensee for Damage or Injury, which states: “In any civil proceedings against a licensee arising out of damage or injury caused by induction or electrolysis or in any other manner by means of electricity generated, transmitted or distributed by a licensee, such damage or injury is deemed to have been caused by the negligence of the licensee, unless there is credible evidence to the contrary . . .” Remember you read it here first.