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Comment by fleventynine | Hacker News Reader

I strongly recommend against this unless you have bonded earth connections between the buildings. During a storm the ground potential between the locations is likely to exceed the 1500V rating of the magnetics in your switches, and your equipment will be destroyed. Fiber is the only safe option at this distance.

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In my country lightning strikes are rare, the equipment on each end of the link costs substantially less than a fiber splicing machine, and we get bonded earth connections as a matter of course.

I agree it's worth keeping an eye on your earthing, of course - if you get a noticeable difference in ground potential and you plan to plug in an EV charger outside in the rain, you might need some extra grounding. Unless your garage, your EV and yourself are all on an insulated concrete slab.

Voltage differentials in the earth that exceed 1500V will occur even without a lightning strike, and the greatest danger is when the ground is dry. Even something as simple as a strong wind blowing on a tree can charge things up significantly...

How interesting! How do old-fashioned wired telephones and cable TV deal with this problem?

The cable TV shield is grounded where it enters the house. The POTS lines aren't grounded (they're differential, like 1000base-T), but the telephone company installs some sort of protection device in the exterior box that allows sparks to jump across to the local ground if the voltage differential gets too high.

It’s so frustrating the amount of over generalization, anecdata that’s actually dangerous, and/or outright misinformation in this thread. Thank you for being one of the folks with spot on accurate info!

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