Basically there are two types of arrester , namely Direct arrester (Lightning arrester) &
indirect lightning arrester (surge arrester).
Direct arrester are copper rod of 5 to 6 feet long used to protect the structure, building, etc. It has
pointed shape at the end to make current density at tip maximum and the bottom part is properly
grounded.
Indirect lightning arrester are those used in parallel to the equipment to protect them from sharp
increase of voltage. It has an gap which make a short circuit path for current to flow to ground
when a high voltage is applied or induced across it. For an example, if the lightning falls on the
transmission line away from transformer. the heavy current flow through the transmission line to
the transformer. If a lightning arrester are not installed in parallel to the transformer, transformer
may get burn.
Note here lightning is indirect for transformer.
