Has anyone installed Surge Protection at AC panel?

I use a whole house protector from Joslyn Electronic Systems; the Joslyn gas tube discharge primary arrestor is internally fused so it is bridged directly across the incoming primary 120V legs, with a connection to service ground. This is only a primary arrestor however; no single unit can be relied upon for complete protection (there is no such thing actually) - you must cascade your protection devices. I use Chang line conditioners as secondary arrestors downline from the primary Joslyn, which is actually downline from the power company's MOV on the incoming 2300V prior to the transformer. The Chang's also contain large internal MOV protectors. In addition, I bridge my own GE V130LA20B MOV across the outlet of my dedicated AC line. So there are actually four modes of protection in all. This is not to say that I'm immune from lightning transients; damage can still occur from a direct hit or a closeby hit, so I power off & unplug all my equipment when storms are nearby. But this protection makes the difference between repairable damage & total catastrophe. Smaller transients & power line surges are of course shrugged off without incident.
I can provide you the model # of my Joslyn, but it's at home so I'll have to check on that. It's an older industrial model but they still build similar products today.

i have a levington device wired directly to my main panel through a 30 amp 2 pole breaker. you can see one at smarthome.com link to

http://www.smarthome.com/4860.html

like bob, i unplug (my hydra) during wacky weather and when i leave town, and when i have wacky friends over.

unpluging is the only truly secure method to avoid damage from ligtning.

sounds like a safe-sex ad.

This is not as easy a DIY as it seems. First, you have to determine the appropriate method of protection (Line 1 to Neutral, L2 to N, L1 to G, L2 to G or L1 to L2). Then you have to know the available short circuit (symmetrical) current available (most devices are limited to 25,000 amps) and there has to be a breaker space available for the device itself UL listed for one or two wires per terminal.

I'm not sure I understand your question: do you want the entire service protected or just the 50-amp dedicated (sub?)panel? If you want the service entrance protected, there is no need to protect the subpanel. If you want just the subpanel protected then this panel has to have an equipment ground bar with a grounding conductor back to your service panel.

I would retain a consulting engineer to anaylize what you have and to give you something to take to an electrician.

As far as whole house models available, I prefer the Square_D "SurgeBreaker Plus" model SDSB1175C.

I put in a 200amp unit for my whole house. It definitely works. I've never blown a power strip/fuse/surge protector since. The unit cost about $400 and took the electrician 1/2 day to install. It's worth it.

It still will not prevent spike within each circuit. You will still want a line conditioner for your system to clean up the little stuff.