create table ORARI
(
    id int identity(1,1),
    ora varchar(10)
)

insert into ORARI
select ('01.50')

insert into ORARI
select ('17.20')

insert into ORARI
select ('3.30')

select (sum(T.ore) + floor(sum(T.minute) / 60)) as ORE, (sum(T.minute) - (60 * floor(sum(T.minute) / 60))) AS MINUTI
from
(
select *, 
CAST(left(ora, charindex('.',ora)-1) as int) as ore, 
CAST(substring(ora, charindex('.',ora)+1,2) as int) as minute from orari

) T