what is the difference between dry type lighting transformer and dry type LT transformer????

It the same principle. Lighting trafo is either cast resin or vacuum impregnated. Is is smaller in size, generally 100 kva our less.

LT signify low voltage where primary and secondary are below 1000v.

Dry type signify that the cooling medium for the core is air and not liquid, thus the terminology "dry".

Dry type may be high voltage, high voltage / low voltage or low voltage as per Low Tension meaning low voltage.

Both are aircored and if it is Vacuum impregnated there is no difference only in rating and voltage ratios and other protection and control accessories as applied..

lighting transformer is used exclusively for lighting.