Has anyone ever seen high voltage power lines sparking from dampness in the air? Neat where I live are some of these high voltage transmission lines. One time I remember we worked at a roadside stand for a race, to provide refreshments one morning. It was foggy out and someone mentioned how you could see small arcs on the lines from the fog.

I just thought of that recently, and thought it was interesting to see. I believe you could hear small arcing as well.

Anyone seen/heard of this?

Any arcing means there is a huge fault in the system and needs to be fixed ASAP, as it is asking for a disaster (fire, electrocution,...). Some exception may be very strong wind swaying the wires on a not well designed line (mainly those below 30kV, where the wire distance does not have to be that large) and on the lightning arrestors (usually in the form of a piece of wire installed intentionally close to some grounded structure to form a spark gap arrestor) in case lightning is around the area (it does not have to directly hit the line, induced voltages are high enough to neeed to be clamped by the spark gaps), but just a humidity or rain, regardless how severe, should never cause any arcing at all.
So if you do see arcing and it is not really unusually windy or stormy, it means something severe happened to the line, so you should report it to either the operator if you know it, or to emergency line.

But what you "smell" and/or "hear" is not sparking per se, but a corona. It is also a problem, but more of an air (mainly NOx and ozone are emitted) and EM pollution (it causes noise in the radio spectrum), power losses and accelerated corrosion of the equipment (the NOx and mainly the ozone, as well as the atomary oxygen are quite aggressive oxidizers). But it is not a direct safety thread. With some really high voltage (400kV and above) it may be unavoidable with some weather, but generally the design of the equipment should minimize it.

Has anyone ever seen high voltage power lines sparking from dampness in the air? Neat where I live are some of these high voltage transmission lines. One time I remember we worked at a roadside stand for a race, to provide refreshments one morning. It was foggy out and someone mentioned how you could see small arcs on the lines from the fog.

I just thought of that recently, and thought it was interesting to see. I believe you could hear small arcing as well.

Anyone seen/heard of this?

Yeah that normal when not state of the art armatures are used or the armatures are dirty. Transmission lines have voltages upwoards of 100kV. At these voltages small inregullaritis and not round parts of armatures will shoe coroana discharge. Damp air has a lower dielectric strength then dry air, so there it is more prominent.

Yes, I pass it every morning! 😃, while cycling to work along Winsford industrial estate, there’s a 132,000 V transmission line to my right, on a couple of the towers you can hear arcing in the insulation strings and cables joints 😎, I’ve yet to see a noticeable corona ?, but you can definitely hear the power flowing through them!

Corona discharge makes the same buzzing as an electric arc.

My aimless wandering through random readings once brought me to a scan of a 1978 book on the subject of North American unipart porcelain insulators, and the book thoroughly explains how breakdown resistance was first viewed as a matter of keeping the insulator dry, and early designs reflect that. In fact the now ubiquitous porcelain insulators on 25kV power lines are quite old in design. The underside isn't directly exposed to rain, but contaminants can still accumulate underneath. Those contaminants, when damp, ruin the insulator's properties by literally "shorting" part of the porcelain surface. Then corona discharge or even flashover can occur.

Suspension-type insulators had the same problem... except when used horizontally! Turns out these stay clean thanks to rain, eliminating the dirty, "shorted" sections.

I remember one evening in Portland Texas seeing the corona discharge from the distribution lines where the cables attach to the insulators.  Seemed every insulator on every pole was buzzing in that humid sea salt air.