Distance Protection

[abrowaqas]

Why Distance( Impedance) protection is always preffered in the Transmission Lines protection?

As for as Short TL is concern, Sometimes we use distance as well as differential protection, but in Medium and Long Transmission Lines only Distance protection is used .. why is it so? whats the reason behind ?

[dlgoff]

What's the difference between the two schemes? What element in the of differential protection scheme that isn't used in the distance scheme?