Lightning may well strike your customer
All UPS is not created equal, argues Christophe Jammes
Many resellers and end users of uninterruptible power supply (UPS) systems believe that they automatically protect valuable equipment and data against lightning-induced power surges.
But it's not quite that simple.
Most of Europe can expect to suffer between two and 10 lightning strikes per square kilometre each year. The chances of a particular building or installation suffering a direct lightning strike are quite small, but a direct strike is not needed for sensitive electronic equipment to be damaged.
A strike anywhere in the vicinity can induce enough of a surge into the supply system to do real damage.
The problem is that some UPS is only effective for surges that occur between the line and neutral of the supply. In real life, however, damaging lightning-induced surges are much more likely to be common-mode surges that occur between neutral and ground, or between the line and the ground.
Bargain-basement UPS often provides no protection at all against common-mode surges. The best UPS may cost a little more, of course.
There are a few more things to think about if you want to be sure that UPS will protect your customers.
Vague claims such as "also provides protection against power line surges" are meaningless. Instead, look for harder information, such as compliance to international standards such as IEC 61643-1 for Low Voltage Surge Protective Devices, and the performance rating, usually shown in kV on the packaging.
No surge protection device can provide total protection against lightning-induced power surges. The energy induced by a nearby lightning strike is simply too great.
A good UPS will, however, suppress most surges without itself becoming damaged. For larger surges, it will also offer one-off protection, where the surge protection device it contains does its job of protecting the connected equipment, but is destroyed in the process.
It is essential for the UPS user to know when such a one-off event has occurred as they are left without surge protection afterwards, even though the UPS may appear to be operating normally in every other way.
Responsible UPS manufacturers provide a warning device, such as an LED indicator, to show when the surge protection in their products is no longer working. It is inadvisable to depend for surge protection on a UPS that does not have it.
UPS will do an even better job if used as part of a comprehensive surge protection system incorporating several levels of protection.
High-energy protection devices can be installed at the point where the supply enters the building, and smaller devices installed at other critical points throughout the building's power distribution system.
Christophe Jammes is an EMEA product manager at Eaton