What is the difference between Surge Arrester & Lightning Arrester?

Lightning arrestor is installed outside and the effect of lightning is grounded, where as surge arrestor installed inside panels comprising of resistors which consumes the energy and nullify the effect of surge.

Transmission Line Lightning Protection:

• The transmission line towers would normally be higher than a substation structure, unless you have a multi-storey structure at your substation.
• Earth Mats are essential in all substation areas, along with driven earth electrodes (unless in a dry sandy desert site).
• It is likewise normal to run catenaries(aerial earth conductors) for at least1kM out from all substation structures. Those earth wires to be properly isolated electrically to each supporting transmission tower, and bonded back to the substation earth system.
• It is important to have the catenary earth conductors above the power conductor lines, at a sufficient distance and position that a lightning strike will not hit the power conductors.
• In some cases it is thus an advantage to have two catenary earth conductors, one each side of the transmission tower as they protect the power lines below in a better manner.
• In lightning-prone areas it is often necessary to have catenary earthing along the full distance of the transmission line.
• Without specifics, (and you could not presently give tower pictures in a Post because of a CR4 Server graphics upload problem), specifics would include:

Structure Lightning Protection:

• At the Substation, it is normal to have vertical electrodes bonded to the structure, and projecting up from the highest points of the structure, with the location and number of those electrodes to be sufficient that if a lightning strike arrived, it would always be a vertical earthed electrode which would be struck, rather than any electrical equipment.
• In some older outdoor substation structures, air-break isolator switches are often at a very high point in the structure, and in those cases small structure extension towers are installed, with electrodes at the tapered peak of those extension towers.
• The extension towers are normally600mm square approximately until the extension tower changes shape at the tapered peak, and in some cases project upwards from the general structure2 to6 metres, with the electrode some2 to3 metres projecting upwards from the top of the extension tower.
• The substation normally has a Lightning Counter – which registers a strike on the structure or connected  to earth conductors, and the gathering of that information (Lightning Days, number per Day/Month/Year, Amperage of each strike)

Lightning in a System is a type of Surge.

So Lighting Arrestor is related to only Lighting. It is usually used at the Entrance or Departure Side of an Electrical Grid. It is also used at top of the Buildings.

Surge arrestor has vast applications; it is commonly used in Communication Engineering to Protect Low Power Systems from High Power Systems working / running in Parallel.