4/0
4
3/0 or250 aluminum
For Service Entrance Cable 600 kcmill (Thousands of circular mils).
A 100 amp service requires that you use AWG 4 copper wire or AWG 2 aluminum wire.
Use AWG #1 copper service entrance wire and #4 copper ground wire.
For a 100 Amp breaker panel it would be 2 AWG. For 150 Amps it would require 2/0 (2 ought) aluminum wire.
3/0 or250 aluminum
Don't use aluminum wire inside the house.
Awg #6
Wire size is rated by Amperes of current. You did not mention the wire size of the aluminum wire, so there is no way to answer your question. The voltage rating is more a rating of how good the insulation around the wire is.
For Service Entrance Cable 600 kcmill (Thousands of circular mils).
A 100 amp service requires that you use AWG 4 copper wire or AWG 2 aluminum wire.
Use AWG #1 copper service entrance wire and #4 copper ground wire.
For a 100 Amp breaker panel it would be 2 AWG. For 150 Amps it would require 2/0 (2 ought) aluminum wire.
40 amp
#2 aluminum for 100 amp
2 AWG Aluminum.
4 sets of 750 mcm aluminum. Or four parallel runs of 600 MCM copper.