Cell Tower Related Lightning Damage
September 18, 2009 04:56 PM
This is out-takes from a recent letter addressing
cell tower lightning and equipment
damage...
Dear XXXXX,
This letter is a supplemental written finding regarding the XXXXXXXXXX Police Dept. site we visited on September 17, 2009....
....IEEE defines sites by exposure categories. The 400’ tower makes this site what we call a Category E location. Please refer to our website slide show: IEEE Exposure Categories
Please note the energy waveforms on the bottom of the slide showing increased duration of the surge/transient/lightning event as the location moves from Category C to Category E. We classify this site as Category E. This makes proper grounding and bonding of all elements on this site extremely critical. The fact that the tower ground and nearby electrical services are not bonded properly will continue to present extreme and potentially damaging voltages to not only the suppression but, the owners electrical and electronic equipment.
As with all sites with large towers, the lightning risk goes up significantly because of the tower itself. Our data shows that most of the lightning strikes near this tower will hit this tower first and not nearby structures. Lightning is a variable event (below 5kA to 150kA and beyond) however most of the high-energy strikes (100kA and up) will hit the tower first are not going to strike nearby structures. The addition of any form of lightning rods on the structures directly below the tower is unnecessary and a waste of funds...
While the electrical equipment may not get struck directly by lightning, there will be severe voltage rises at electrical equipment with ground/bonding issues AND there will be significant ‘magnetic coupling’ on all copper conductors (wires and processors) anywhere near or under this tower. This means lightning just has to hit the tower to induce damage on nearby electrical and electronic equipment. Typical Unbonded Condition
Even a small ground potential differential between the tower and the service ground with the high energy potential at this site would produce significant voltage rises at our suppressor on the main. We recommend the tower ground be tested and enhanced until is has be established as equal potential to the electric service ground and then, both must be bonded to each other. by two large copper conductors. We also recommend the addition of the Potential Equalization Clamps (PEC150) on each of two bond conductors and a bonding bus bar to land both bonds devices. Proper Grounding and Bonding
All telecom/data and electric services must be bonded together. The multiple electric and telecom service rooms through out this site present the next bonding problem that needs to be addressed. The lack of bonding of the separate phone rooms throughout the facility still remains an issue. We found ‘floating’ or ungrounded phone and data equipment during our inspection. We recommend the addition of a bonding bus bar in each equipment room, a connecting bond ‘jumper’ between all equipment rooms and the use of the PEC100 at each bonding jumper.
The existing mixture of different suppression manufacturers surge products on this site is the next problem to be addressed. It is not that uncommon when mixing suppressors of different technologies that coordination becomes a big issue. Most manufacturers will not warranty their surge products when used in combination with other surge manufacturers products. This is not a marketing plot. Coordination of the different technologies is a problem. Each manufacturer works under different design and component parameters, clamping levels, and surge reaction times. Within the suppressor itself, the ‘matched array’ of components is critical to overall product life and performance. This same ‘matched array’ rule applies to the entire suppression system for any given building. We highly recommend a uniform and coordinated approach to suppression design. The piecemeal mixture of surge products on this site will always be a problem...
Most of the plug in suppression used throughout the site is UL Listed as temporary power taps and not surge suppression (UL1449). Go to our website: Marketing MisInformation for more information on plug in suppression issues. The age of the plugins coupled with the technology used on these suppressors would now render them useless as protection. They will never show status light failure since they are UL listed as extension cords. They should ALL be replaced.
In conclusion, the high risk of lightning exposure due to the tower coupled with the ‘mission critical’ nature of this site makes coordinated and comprehensive protection critical to success. We highly recommend the development of a master plan and master specification for all grounding/bonding and surge suppression applications throughout this site.
If you have any questions, please feel free to call our toll free number, 800-934-9354.
Dear XXXXX,
This letter is a supplemental written finding regarding the XXXXXXXXXX Police Dept. site we visited on September 17, 2009....
....IEEE defines sites by exposure categories. The 400’ tower makes this site what we call a Category E location. Please refer to our website slide show: IEEE Exposure Categories
Please note the energy waveforms on the bottom of the slide showing increased duration of the surge/transient/lightning event as the location moves from Category C to Category E. We classify this site as Category E. This makes proper grounding and bonding of all elements on this site extremely critical. The fact that the tower ground and nearby electrical services are not bonded properly will continue to present extreme and potentially damaging voltages to not only the suppression but, the owners electrical and electronic equipment.
As with all sites with large towers, the lightning risk goes up significantly because of the tower itself. Our data shows that most of the lightning strikes near this tower will hit this tower first and not nearby structures. Lightning is a variable event (below 5kA to 150kA and beyond) however most of the high-energy strikes (100kA and up) will hit the tower first are not going to strike nearby structures. The addition of any form of lightning rods on the structures directly below the tower is unnecessary and a waste of funds...
While the electrical equipment may not get struck directly by lightning, there will be severe voltage rises at electrical equipment with ground/bonding issues AND there will be significant ‘magnetic coupling’ on all copper conductors (wires and processors) anywhere near or under this tower. This means lightning just has to hit the tower to induce damage on nearby electrical and electronic equipment. Typical Unbonded Condition
Even a small ground potential differential between the tower and the service ground with the high energy potential at this site would produce significant voltage rises at our suppressor on the main. We recommend the tower ground be tested and enhanced until is has be established as equal potential to the electric service ground and then, both must be bonded to each other. by two large copper conductors. We also recommend the addition of the Potential Equalization Clamps (PEC150) on each of two bond conductors and a bonding bus bar to land both bonds devices. Proper Grounding and Bonding
All telecom/data and electric services must be bonded together. The multiple electric and telecom service rooms through out this site present the next bonding problem that needs to be addressed. The lack of bonding of the separate phone rooms throughout the facility still remains an issue. We found ‘floating’ or ungrounded phone and data equipment during our inspection. We recommend the addition of a bonding bus bar in each equipment room, a connecting bond ‘jumper’ between all equipment rooms and the use of the PEC100 at each bonding jumper.
The existing mixture of different suppression manufacturers surge products on this site is the next problem to be addressed. It is not that uncommon when mixing suppressors of different technologies that coordination becomes a big issue. Most manufacturers will not warranty their surge products when used in combination with other surge manufacturers products. This is not a marketing plot. Coordination of the different technologies is a problem. Each manufacturer works under different design and component parameters, clamping levels, and surge reaction times. Within the suppressor itself, the ‘matched array’ of components is critical to overall product life and performance. This same ‘matched array’ rule applies to the entire suppression system for any given building. We highly recommend a uniform and coordinated approach to suppression design. The piecemeal mixture of surge products on this site will always be a problem...
Most of the plug in suppression used throughout the site is UL Listed as temporary power taps and not surge suppression (UL1449). Go to our website: Marketing MisInformation for more information on plug in suppression issues. The age of the plugins coupled with the technology used on these suppressors would now render them useless as protection. They will never show status light failure since they are UL listed as extension cords. They should ALL be replaced.
In conclusion, the high risk of lightning exposure due to the tower coupled with the ‘mission critical’ nature of this site makes coordinated and comprehensive protection critical to success. We highly recommend the development of a master plan and master specification for all grounding/bonding and surge suppression applications throughout this site.
If you have any questions, please feel free to call our toll free number, 800-934-9354.
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