I am looking for more information on the following: The green strand passes through a induction furnace under tension. For example equipment provider of induction furnace for this purpose. More information on the type etc.
Your question is not clear to me. The following graphic may be of assistance:
FYI - most (all?) 7-wire strand for prestressed concrete manufactured today is low-relaxation - which has both stress-relieved properties and also lower relaxation properties than just S-R strand.