» The nine recognised power problems «

Definition of the nine types of power fluctuation

Power surges (and spikes)

A power surge takes place when the voltage is 110% above normal. These surges are short duration spikes in the mains supply voltage, typically a few milliseconds in less. In general, day to day occurrences of these higher voltages causes wear and tear of components and, inevitably failures.

Note that vendors have there own idea of what a what a spike and what a surge is. One definition put a 'spike' as being under 3 nanoseconds, and a 'surge' as over 3 nanoseconds. Given a nanosecond is one billionth of a second…

Either way, if the peak is high enough or repeated often enough, it can inflict heavy damage to electric devices. Think of a light bulb. If you turn a light on and leave it, it may well last for months, even years. However - not that I recommend this for a moment - if you sit for any length of time flicking the light on and off every few seconds the same bulb would soon burn out it's filament. These daily surges and spikes in electricity similarly put extra strain on the delicate components of computers, wearing them down over time.

Over voltage (spikes)

Also know as a 'swell', these are caused when high-current electrical equipment, such as vacuum cleaners, laser printers, photo-copiers and air conditioners are switched off. The over voltage is caused by all that extra power dissipating through the rest of the power circuit, momentarily swamping any other electronics running at the time.

In regard to 'over voltage', I believe the term properly applies when the line condition lasts for minutes or even days, often due to intentional changes by the power utility companies in answer to expected needs.

Switching transient (instantaneous under voltage spike)

These are spikes, but of very, very short duration - typically mere nanoseconds, though the peak can apparently be as high as 20,000 volts. Two common causes are arcing faults (in the overhead power lines, I think) and static discharge. In addition, major power system switching disturbances, initiated by the utilities to correct line problems, may happen several times a day, depending where you live.

A number of UPS manufacturers class high voltage spikes under this, classing it as a sudden, rapid voltage peak of up to 6,000 volts. Think lightning here.

Lightning strikes (spikes)

There seems to be some disagreements over whether a lightning strike is an over voltage, a surge or a switching transient. Lacking a degree in electrical engineering I haven't found a definitive answer yet, but the more I read in-depth the more I'm inclined to think the marks in the sand are written by UPS manufacturers based on what 'their' range of products protect against.

Anyway, as far as spikes goes, lightning is about as bad as it gets. I recall one incident years ago when, I believe, a particularly strong bolt hit a transformer. Locally, a large number of computers were damaged, and indeed a number of shops are known to have lost a days money because it also destroyed and/or wiped the ePDQ and EPOS machines, erasing all record of the mornings takings.

Note that few, if any UPS's can survive a direct lightning strike. If the storm is right over your house or business and you can, best to unplug it, just in case! Basically, unless your surge protector or UPS specifically and unequivocally states it will fully protect you against one, you can assume it won't!

Power failure or blackouts

This is as it suggests, a complete loss of mains power. These are clearly out of your hands but causes include everything from weather conditions like lightning storms or ice on the power lines, excessive demands on the national or regional grid and localised faults caused by cable failure or accidents.

However, if you are just recalling the long power strikes of the 70's in the UK, think again. A break in the mains supply of mere milliseconds is sufficient enough to disrupt, crash, lock or reset a computer.

This break is like unplugging or turning off your computer without shutting it down properly only a tad worse and, as well as the loss of all unsaved work, can corrupt your File Allocation Table (FAT).

For the uninitiated, unless you pay an expert to fix the mangled FAT, this baptism of fire tends to mean your drive needs to be reformatted and everything re-installed to get it working again. OK, that's maybe a morning lost for each out of action machine. It also means that unless you are methodical (and/or paranoid) and have a good - current - backup, according to your circumstances, you have just lost…

All your emails, favourites, contacts etc
the save games of whatever you've just spend weeks trying to beat
priceless digital photos
your college work and thesis
the day's spreadsheets
weeks of tedious data input
the year's entire accounts in Sage - costing you your business

All gone, perhaps forever…
I hope you did a recent backup of everything!

If you are thinking this is just scare tactics, think again. Besides the fact I've nothing to gain, the simple truth is that I have seen all the above happen all too often - including the last example - twice! True, I can't honestly say one way or the other if electrical spikes, sags etcetera caused these, but given the statistics give it a 60% probability…

As a side note, whether though ignorance or laziness, for those of you do that just turn off Windows without properly shutting down first, this is what WILL happen one of those times. Don't say I didn't warn you!

Power sags

Power sags involve voltages 80 to 85 percent below normal for a short period of time and are one of the more common forms of disturbances. These can and do upset sensitive equipment like computers, causing them to lock or hang, with the associated data loss from the necessary system reset. For resets, see also my warning above under 'power failure and blackouts' about the dangers of corrupted FAT.

Brownouts are rather more unpleasant in that these are long term sags in the mains supply voltage which can last up to several days. Brownouts are classed as 'under voltage'.

Under voltage - brownouts

These are caused when power hungry items like vacuum cleaners and photocopiers are turned on, greedily sucking up the immediate distributed voltage - at the cost of whatever else is running at the time. Under voltage can also occur during times of peak power demand. Apparently under voltage is particularly hard on components that use motors, like CD players, VCRs and DVD players.

I believe the term properly applies to brownouts where the line condition lasts for minutes or even days and is due to intentional changes by the power utility companies, reacting to conserve and balance power during peak demand periods.

Also for other heavy loads that exceed supply capacity - the one that comes to mind is a truly massive draw during a major television event. The first time the commercial break came on a million odd thirsty Brits turned on their kettles for a cuppa… Truth!

Line Noise

Typically caused by EMI and RFI waves, this is electrical noise of high frequency waveform and can cause severe disruptions to electrical circuits and equipment. These random, sporadic, or multi-frequency electrical signals can become part of a transmission interrupting and/or corrupting the original signal and causing undesirable effects in circuits of computer systems.

These impulses travel through the air and data cables - especially unshielded ones - can pick them up in the same way that an antenna picks up broadcast signals. These conducted EMI and RFI impulses create background noise on the data cable, interfering with communication between workstations, servers and other peripherals; this can be particularly hard on hubs and routers.

Causes include welding devices, various types of motors and motor control devices, microwaves, lightning, radio and other broadcast transmitters/transmissions, fluorescent lights, and even the computers power supply.

Ever seen a film or movie (like Small Soldiers or Oceans Eleven), or even perhaps the 'Dark Angel' TV series where an EMP device or weapon destroys the terrorising robots, disrupts a city, or even causes global chaos and a breakdown in society by wiping out all the computers… ? Well, that's just line noise on a grand scale!

Frequency variation

Apparently defined as fluctuations of more than 5% (of the regular 50Hz or 60Hz) from the normally stable utility frequency. Reading up, they mainly appear to result from generators or small co-generation sites being loaded and unloaded. Also attributed to erratic operation of emergency generators or unstable frequency power sources.

Again, for sensitive electronic equipment, the result can be data corruption, hard drive crash, keyboard lockup, erratic operations and program failure and even component damage.

Harmonic distortion

Harmonic distortion is the change of the AC voltage waveform from a simple sinusoidal to complex waveform and can be generated by a load and fed back into the AC mains, causing power problems to other equipment on the circuit. These voltage harmonics can cause communication errors and hardware damage due to unexpected overheating of components.

On top of this are 'In-Between Harmonics' which also cause overheating, voltage fluctuation, and visual flicker in computer monitors (and fluorescent lighting and other arc lighting). Perversely they're often caused by the instruments you need to improve power quality.

Pointing to the increase need for on-line UPS's in factory and industrial environments, other sources producers of harmonics include rectifiers, inverters, adjustable-speed motor drives, welders, arc furnaces, voltage controllers, and frequency converters. That said, I read that point-of-sale terminals can cause them too.