pserc lightning protection: a stroke of luck? theory and application: customer side low voltage...
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PSerc
Lightning Protection: A Stroke of Luck?
Theory and Application: Customer Side
Low Voltage Systems
Ward Jewell Wichita State University
APPA 2005 ENGINEERING & OPERATIONS
TECHNICAL CONFERENCEApril 18, 2005
Power Systems Engineering Research Center
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TV station$50k damage every
year
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Lightning will strike
Lightning rods may help prevent burn damage to structures
Other devices may reduce number of strikes
But…lightning will strike
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Poortower
ground
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Poor Tower Ground
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bends
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boltedconnections
Poor Tower Ground
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Poor Tower Ground
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highvoltage
Can we insulate?
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~1,000,000 V
Can we insulate?
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~1,000,000 V
Can we insulate?NO!
voltage is too high
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Lightning will flow to earth.
Insulation will not stop it.
Keep it away from sensitive equipment
by giving it other paths to earth.
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Improve tower ground
TransmitterOne groundrod close to each leg
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Exothermicweld
(cadweld)conductorsfrom tower
to rods
Improve tower ground
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Improve tower ground
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high voltage
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Bond tower grounds
to building grounds
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Bond all grounds to service entrance
ground
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high voltage
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Bond cable shield to tower
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high voltage
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Bond cable shield tobuilding steel
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Surge suppression:everywhere a conductor
entersthe facility:
secondary surge arrestors
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Surge suppression:everywhere a conductor
entersthe facility:
secondary surge arrestors
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Surge suppression:at sensitive equipment:transient voltage surge
suppressors(UL 1449 listed)
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Provide all possible safe paths to earth;
place surge suppression at the others
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Bond cableshield to tower
Improvetower
ground
Bond all grounds to service entrance
building steel
SurgeSuppression
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Move service
entranceto ground
Or, even better, move all conductor
entrancesto one location at ground
level,through grounded copper
bulkhead.
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Lightning Protection: Customer Side Low Voltage Systems
Lightning will strike– rods or other devices will not stop all strikes
Lightning will flow to earth– insulation will not stop it
Keep it away from sensitive equipment– Provide safe paths to earth
– Bond all grounds
– Use arrestors and suppressors
» service entrance arrestors
» sensitive equipment suppressors
PSerc
pserc.org
APPA 2005 ENGINEERING & OPERATIONS
TECHNICAL CONFERENCEApril 18, 2005