Eye Current

Lightning Season

This is the time of year when most of us worry the least about our biggest nemesis, lightning. Although winter is the the least likely time that lightning is apt to do its dirty deed, spring is just around the corner. While lightning can strike at any time, the season peaks in most areas around May to June.

While lightning is often described as an act of God, there is still a lot we can do to minimize and prevent damage. Most of the damage caused by lightning is not caused by a direct hit to the equipment involved, but from the eddies and offshoots as the massive energy source seeks to discharge itself into the the earth.

Prevention requires a three prong attack. The first is grounding, the next is isolation, and the third is surge protection.

1. Probably the most important item in lightning protection is grounding. Neutrals should be grounded before the power enters the building. Some systems specify very distinct grounding schemes. Foxboro's Foxnet systems specify separate AC and DC grounds. Building grounding should be checked by a qualified electrician at least once a year. Communication cables should be should be grounded per spec, typically one end only. The installation manual is your friend.
2. If possible all copper communication that enter or leave a building should be replaced with fiber optic cable where ever possible. While field wiring isn't easily replaced by fiber, twisted pair fieldbus and standard ethernet wiring is easily replaceable with standard components and fiber cable. Sometimes it makes sense to replace some of the cabling between cabinets within the same building. Running fiber between cabinets on short runs can isolate the lightning hit damage to one cabinet.
   
3. Surge protection devices can protect the equipment from surges coming down a power line from a hit miles away. Unfortunately we may not be as protected as we would like to believe. Most surge protection devices depend on MOVs. These devices are limited in the protection that they provide and occasionally will actually catch on fire. A big limitation on them is that each time they are activated, they are weakened, so one never really knows just how much protection an MOV has left. A company called Zero Surge provides state of the art surge protection devices. The company's protection devices use blocking methodology instead of trying to shunt away the excess energy. The blocking technology uses phase shifting to effectively blocks high speed, high energy pulses from the line supply. While these surge protectors may seem pricey, they do promise to give real protection instead of possible protection to mission critical and expensive equipment. Zero Surge's FAQ explains:
   

   There are basically two types of powerline surge technology, patented Series Mode and the older Shunt Mode (so-called hybrids are usually Shunt Mode). The Shunt Mode technology was developed over thirty years ago to protect standalone equipment, but this older technology is no longer suitable for modern sensitive interconnected equipment.

   Shunt Mode suppressors are still very common because this older technology is inexpensive to manufacture with high profit margins, and as long as people can be seduced by the low prices, these products will continue to be sold. They generally divert powerline surges to the safety ground wire, using circuits described as "All Three Modes of Protection". The resulting surges diverted to the ground wire can exceed 1000 volts, exposing sensitive motherboards and data boards to surge disruption, degradation and damage.

   This surge voltage on the ground wire varies along the length of the wire. When equipment such as modems, printers and other computers is interconnected, the interconnecting cable creates a "ground loop". If the surge induced on the safety ground wire of one computer is 1000 volts and the surge induced on the safety ground wire at another location is 600 volts, then the difference of 400 volts is fed into the interconnecting cables causing the disruption, degradation, or damage.

   While large surges will cause damage, small surges can result in data problems such as lock-ups, data errors, and "mysterious problems".

   It is better to avoid Shunt Mode surge suppressors that claim "All Three Modes of Suppression" than to try and live with the problems they cause when they divert surges to the ground wire.

Defending against lightning is real preventive maintenance and can be a real downtime and money saver. If you would would like more information or to purchase real surge protection devices drop us an email. We can assist in inspection and in providing the proper hardware.

posted by Ray L. @ 3:02 PM