Applicable to protection equipment having coded bit serial data transmission for exchanging information with control systems. Specifies a companion standard enabling interoperability between protection equipment and devices of a control system in a substation. The specified companion standard uses standards of the IEC 60870-5 series. Submits specifications for informative interface of protection equipment, but is not necessarily applicable to equipment combining protection and control functions in the same device sharing a single communication port. Covers two methods of information exchange, one based on explicitly specified application service data units, and the second using generic services for transmission of almost all possible information.