Camera Lightining Protection

Unbridled

Senior Member
Location
Tampa, Fl
Looking for a reason,
Last week a lightning hit several poles approximately 100-150 feet awayfrom our cameras(mounted on the poles) and destroyed them.

To protect the cameras we have on each pole, one 8 FTground rod with #8 ground wire and L-comm lightningprotectors http://www.l-com.com/surge-protector-compact-weatherproof-10-100-1000-base-t-cat6-gas-tube-lightning-protector-rj45-jacks(ALS-CAT6JT and ALS-CAT5W) but they failed to protect the cameras.
Site visit showed no signs of loose connections.
Any suggestion's or logical reasons for the failure?
Thanks in Advance

 

cuba_pete

Senior Member
Location
Washington State
Looking for a reason,
Last week a lightning hit several poles approximately 100-150 feet awayfrom our cameras(mounted on the poles) and destroyed them.

To protect the cameras we have on each pole, one 8 FTground rod with #8 ground wire and L-comm lightningprotectors http://www.l-com.com/surge-protector-compact-weatherproof-10-100-1000-base-t-cat6-gas-tube-lightning-protector-rj45-jacks(ALS-CAT6JT and ALS-CAT5W) but they failed to protect the cameras.
Site visit showed no signs of loose connections.
Any suggestion's or logical reasons for the failure?
Thanks in Advance
I see no mention of the bonding system you have in place, just protectors and a ground rod at each pole (structure).

Even then a well designed LPS likely won't save a device that is directly affected by the lightning stroke, i.e., within the immediate sphere of influence.

What is the overall design of your LPS? How is it bonded to the GES?
 

Sahib

Senior Member
Location
India
Looking for a reason,
Last week a lightning hit several poles approximately 100-150 feet awayfrom our cameras(mounted on the poles) and destroyed them.

To protect the cameras we have on each pole, one 8 FTground rod with #8 ground wire and L-comm lightningprotectors http://www.l-com.com/surge-protector-compact-weatherproof-10-100-1000-base-t-cat6-gas-tube-lightning-protector-rj45-jacks(ALS-CAT6JT and ALS-CAT5W) but they failed to protect the cameras.
Site visit showed no signs of loose connections.
Any suggestion's or logical reasons for the failure?
Thanks in Advance
The lightning current might have exceeded the capacity of your lightning protector. You did not design the lightning protectors taking into account the statistical lightning intensity in that area.
 

mgookin

Senior Member
Location
Fort Myers, FL
Looking for a reason,
Last week a lightning hit several poles approximately 100-150 feet awayfrom our cameras(mounted on the poles) and destroyed them.

To protect the cameras we have on each pole, one 8 FTground rod with #8 ground wire and L-comm lightningprotectors http://www.l-com.com/surge-protector-compact-weatherproof-10-100-1000-base-t-cat6-gas-tube-lightning-protector-rj45-jacks(ALS-CAT6JT and ALS-CAT5W) but they failed to protect the cameras.
Site visit showed no signs of loose connections.
Any suggestion's or logical reasons for the failure?
Thanks in Advance
What does the manufacturer of the surge protectors say?
 

Sahib

Senior Member
Location
India
Of course
The lightning current might have exceeded the capacity of your lightning protector. You did not design the lightning protectors taking into account the statistical lightning intensity in that area.
to be valid, the lightning protectors might also be damaged by the lightning. If they were not damaged and only the cameras are damaged, then there might be mismatch between the two.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
If I understand the system description, you have a _separate_ ground rod at each lighting pole, connected to a lightning arrester, connected to your equipment.

If this is the case, then there is a very real possibility that the ground rods and the lightning arrester actually _caused_ the problem.

The ground rod is two way; it can couple lightning currents down to the earth, or up _from_ the earth.

During a nearby lighting strike, current has to flow through the earth. A ground rod can conduct such currents up to the lightning arrester, through your equipment, to your electrical supply or signal conductors.

This is why ground rods must all be bonded together.

-Jon
 

junkhound

Senior Member
Location
Renton, WA
logical reasons for the failure:

a. Take the cover off the lightning protector, determine damage if any.

b. if the little ceramic gas tubes are blown apart or the lead solder joints melted away, the lightning strike just 100 ft away was higher magnitude than the capability of the; arrestor.

c. If intact, then there are 5 or 6 prime candidates for the 'why'.
1. The ground system inductance is too high, allowing spikes in the 10's of kV due to having loops or sharp turn on the ground wires. (My first suspect)
2. The sensitivity of your cameras to damage is lower than the few hundred volt spike that occurs on gas tubes - the 90 V is where they fire for a slow rising voltage, such as 100 V per second. Lightning has a rise time of a few mircoseconds, so there is appreciable overshoot on gas tube voltages.
3. There is a conceivable resonance in you system - line inductance and camer capacitance resonate to amplify lightning voltage at the gas tube.
4. As others have said, the grounds may not be tied together properly, allowing circulating currents (and resonances)
5. combinations of the above.

The only way to determine the reason is to test the camera for the voltages and rise times at which they fail, and compare that to the gas tube response and circuit responses.

Installed literally thousands of the little ceramic gas tubes like in you protector on Minuteman sites in the 70's and 80's. NEVER all by themselves though, in every case to protect sensitive comm circuits the gas tubes were followed by LC filters AND movs or avalanche diodes.

I have seen the little ceramic gas tubes survive 10's of kA lightning currents (actually EMP and nuclear lightning) to the extent in some cases the solder on the leads melted and the magnetic forces from the high currents pulled the leads out of the board, etc. The original patents on the type gas tube show in your arrestor was from Joslyn, have seen their tube glowing bright red and still not be destroyed - high alumina ceramic and kovar electrode construction. I have no idea what the type ceramic and metal used for the L-com part is, may be cheap low alumina ceramic and plain steel electrodes which could blow up ?
 

GrayHair

Senior Member
Location
Nashville, TN
Seen it several times. Worst damage always seemed to be at sites without a common ground. My preference was to isolate with fiber, but that was before IP cameras.

We rarely know when lightning protection works, but always know when it doesn't. Maybe it should be called "lightning mitigation"!
 
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