You don't have to be in a thunderstorm to have a shocking experience with an antenna.
When I was an apprentice in a desolate place called Waiouru, we had a dipole strung up outside the workshop. It had the braid of the coax grounded and tapped onto the center wire of the coax was a spark plug with a 0.030" inch gap. (No metrics for me, so I'll let someone figure it out.) In the winter, when the snow clouds were down low, that spark plug was zapping away all day as it discharged the static electricity that had built up on the antenna.
We don't normally get the huge lightning strikes that they get in the USA, because our humidity is higher, so I suggest as a good starting point, you need to start reading some of the ARRL handbooks. Having a high wattage 100k ohm bleed resistor across the antenna to ground is a good start, but you need a fast DC (low resistance ) path to ground if there's any close lightning.
The best solution is not to have your radio connected to the antenna during a thunderstorm. That keeps the expensive item safe. Fixing an antenna or coax is a lot cheaper and simpler.
- Putting static discharge coils between mast-ground and the cores of the 2 dipole feedlines is a no-brainer.
- These presumably really should have some arc-gap or similar lightening protection too ...
- Feedline shield is grounded at the shack only (there is no mast)
- Feedline core is not currently protected at all
- The unun is on the house gable with no ready access to ground and whilst I can run a static discharge ground cable down the outside of the house, I suspect that running something sufficient to ground a lightning strike is less simple and aesthetically acceptable