My question is interrogation group ()COT 21-36) is part of the IEC 60870-5-104 standard or not?
if we look for a definition of this standard:
IEC 60870-5-101 [IEC101] is a standard for power system monitoring, control & associated communications for telecontrol, teleprotection, and associated telecommunications for electric power systems.
• Possibility of classifying the data into different groups (1-16) to get the data according to the group by issuing specific group interrogation commands from the master
IEC 60870-5-104 (IEC 104) protocol is an extension of IEC 101 protocol with the changes in transport, network, link & physical layer services to suit the complete network access.
that mean that standard IEC 60870-5-104 must have interrogated by interrogation group 1 (Cause of transmission ( COT 21-36)) or not , it's not part from the IEC 60870-5-104 standard