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Coping with power viruses

06 October 2010

Power viruses are contracted in much the same way as other viruses – passed along, often by your neighbours on a shared electrical distribution network. Rob Morris describes the six most common types and how to deal with them

Software viruses and their impact on computer systems are well documented. These digital attackers enter unseen, incubate in silence, and then launch an attack ranging from the annoying to the disastrous. Electrical disturbances are similar and could be called ‘power viruses’ since they are also unseen and cause serious and expensive electronic system failure.

Typically, a facility experiences more than 6,000 power viruses a year. Some are obvious, some less so, many are almost unnoticeable, but they all cause problems and challenges that can seriously damage productivity, from lost data and lock-ups to communications errors and hardware failures.

Power viruses are contracted in much the same way as other viruses – passed along, often by your neighbours on a shared electrical distribution network. Some take time to cause noticeable damage; others are immediately catastrophic, like a lightning strike. But how do they impact upon an electronic system and what can you do to prevent them happening? There are six main power viruses, as follows:

Voltage spikes and impulses  Mostly the result of electrical equipment inside a facility; electrical loads like elevators, motors, relays, and so on can cause sudden large increases in voltage inside the electrical system. Conditions outside a facility can be to blame as well. Switching activities by the electricity utility and lightning strikes can cause transient impulses so intense they literally ‘blow up’ sensitive micro-circuitry.

This is deadly to electronic systems, but not always immediately. Sometimes voltage spikes and impulses are relatively small in amplitude, and simply weaken components over time leading to deterioration and eventual failure. Other times, impulses may be so large they cause immediate system failure.

Electrical noise  Like voltage spikes and impulses, electrical noise is generally created inside the facility by the system’s electrical neighbours. Almost every electricity-consuming device contributes its share of electrical contamination. Appliances, photocopiers, printers, even PCs are all noise sources that can cause computers to lock up, lose data, or behave unreliably. It is something of a paradox that computers often infect other computers with power viruses.

Common mode voltage problems  This has not received much attention, but detection of common mode voltage problems is now easier and more problems are being traced to it. It is characterised by unwanted voltage measured between neutral and ground in the electrical system. The virus is probably the most serious one and occurs as a result of high impedance safety grounds, neutral conductors shared with other circuits and branch circuit lengths that are excessive.

When the electrical noise virus appears between the neutral and ground conductors, it becomes a common mode virus and causes lost files, lock-ups or re-boots, communication errors and ‘no problem found’ service calls.

Voltage regulation  Characterised by abnormal variations in the electrical circuit’s nominal operating voltage, these variations are generally greater than +10% of nominal voltage and may last for several line cycles or more. Traditionally, this has been referred to as the ‘sag’ or ‘surge’.

It is typically caused by large loads turning on and off and overloaded branch circuits or distribution transformers. In some cases, voltage regulation viruses can be the responsibility of the power utility. If an electronic system requires tightly regulated voltage (most systems don’t) the voltage regulation virus is likely to cause system lock-ups and unreliable operation in addition to damaged or destroyed components.

Blackouts  The most visible and easily identifiable – one moment power is present, the next it’s not and the system is dead. The effects of unanticipated power loss are obvious. This is especially true if the system is a network or some other ‘fault intolerant’ architecture. Fortunately, blackouts account for comparatively few occurrences of all the power viruses.

Back door disturbances  Back door disturbances infect your system via a secondary path. Even though they are not an ac power connection, things like serial ports, telephone lines, network cabling and I/O connections can all allow power viruses to invisibly enter a system. It causes driver chip failure and communication errors. They often go unrecognised and serious damage can occur.

The magic pill
“An ounce of prevention is worth a pound of cure” – nothing could be closer to the truth when it comes to power viruses. We’re familiar with the damage caused by software viruses and we have learned to practice ‘safe computing’ - backing up data, avoiding clicking on unknown emails, and so on. We also run anti-virus programs, install firewalls and take other preventative measures routinely. So why don’t we apply the ‘safe computing’ approach to the problem of power viruses? They have the same potential devastating effects where systems are concerned.

If there is a ‘magic pill’ to prevent power viruses, it’s clear that prevention must be practised as a ‘system’. This means that certain prevention techniques must be used together. There are five simple devices than can prevent the problems outlined – but all five are required for complete immunity:

Voltage spikes are addressed with a surge diverter and electrical noise with a noise filter. Each of these by themselves, however, is capable only of weakening or slowing down a virus, not eliminating it.

Isolation transformers eliminate common mode voltage problems. When surge diverters and noise filters are added to the isolation transformer, the resulting ‘system’ kills all three viruses.

Uninterruptible power supplies eliminate blackouts, but most are incapable of preventing other viruses. The UPS must be used with other parts of the system to achieve total virus immunity.

The backdoor disturbance can be addressed several ways. Fibre optic connections are one means of electrically closing the back door, but if ordinary copper wiring is used for communication lines, it may be necessary to employ special surge diversion techniques for these connections.

Luckily, the voltage regulation virus is no longer a serious hazard. Once it was responsible for many system failures, but today’s systems use switch mode power supplies. This technology was designed as a way of reducing both power supply size and cost while simultaneously increasing electrical efficiency.

Switch mode supplies are designed to consume electrical power differently than their predecessors. These operational differences have created a beneficial by-product where voltage regulation is concerned. As a result, most systems enjoy substantial immunity to the voltage regulation virus. Additional preventative measures (voltage regulators) are unnecessary.

Power viruses are an appropriate description of the power quality problems that can plague electronic systems. Our dependence on sophisticated technology has created an increased awareness regarding the need to safeguard system integrity. Software viruses have led to the introduction of preventative strategies and data is routinely backed up, and part of this ‘safe computing’ approach should be the prevention of power viruses too.

Rob Morris is country manager, Powervar


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