Kegel was born in Dresden. He studied conducting with Karl Böhm and composition with Boris Blacher at the Dresden Conservatory from 1935 to 1940. In 1946 he began conducting in Pirna and Rostock; and in 1948 he began a three-decade-long association with the Leipzig Radio Orchestra and Choir, of which he became the principal conductor in 1960. Meanwhile, in 1977 Kegel took the position of principal conductor of Dresden Philharmonic Orchestra, which he kept until 1985.
In 1990 he committed suicide in Dresden.
Kegel was married to the Italian soprano Celestina Casapietra from 1966 to 1983. Their son Björn Casapietra is active as a singer, moderator and actor.