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DISCUSSIONlightning surgesurgeprotectorforpowerlineinstrumentlightning surgepower supply cableUVsurgeprotectorforpowerlinelightning surgelightning surgepower supply cableinstrumentUVSingle-pole switchDouble-pole switchDISCUSSIONthundercloudthunderclouddischargemagnetic couplingburied cablefieldsurgeprotectorbuildingsurgeprotectorground surface23Recommended models: • Model MA-100 (100 –120V AC, 2A power supply) • Model MA-200 (200 –240V AC, 2A power supply)Recommended models: • Model MDP-24-1 (4 – 20mA DC signal line) • Model MA-100 (100 – 120V AC, 2A power supply) • Model MA-200 (200 – 240V AC, 2A power supply) • Model MAX-100 (100 – 120V AC, 5A power supply) • Model MAX-200 (200 – 240V AC, 5A power supply) • Model MAX-100 (100 –120V AC, 5A power supply) • Model MAX-200 (200 –240V AC, 5A power supply)QUESTIONDuring a recent lightning storm, the power was turned off but some instruments were still damaged. Can you explain this?Lightning jumped across the single-pole switch into the instrumentation.We would recommend to use a double-pole switch. However, this does not insure that a severe lightning surge will not damage. It is depending on the insulation resistance of the switch or the size of the lightening pulse. The only sure solution is to install a surge protector in line with the power source.7ANSWERANSWERQUESTIONIt has been said that if you use buried cables, then that is enough from light-ning. Is this a true statement?No, because buried cable are also vulnerable to the unpredictable power of lightning.8ANSWERANSWERA buried cable does not have as much pro-tection from induced lightning as one might expect, because underground soil easily transmits an electromagnetic field which oc-curs during a lightning discharge. Also, the high lightning current that is being dis-charged to ground by the lightning rod can find its way to the buried cables located in the ground.

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