IEC 61850 is not the only protocol
by Tom Berry, Schneider-Electric
IEC TC 57 WG 17 is in charge of power system intelligent electronic device communication and associated data models for microgrids, distributed energy resources and distribution automation.
IEC 61850 is not the only protocol …but its data model is a popular reference for identification and mapping.
Outside the somewhat specialized domain of substation automation there are many communication protocols that are used to transmit near real time data values or periodic energy values. Modern meters have a primary role of recording and transmitting energy values for business purposes but today they often have additional communication ports for transmitting values to energy management systems or to interface display. Typically these “instantaneous” values are calculated and reported every one or two seconds. For historical and bandwidth reasons, metering standards such as IEC 60256 (DLMS/COSEM) use an identification system based on a series of numbers called the Object Identification System (OBIS).
However modern internet-of-things and web-based protocols often use text-based encodings where measurement values are identified with human readable character strings. This is the case for the identification of measurement types defined in the Common Information Model: IEC 61970-301 and profiles like IEC 61970-452.
There is ongoing work within IEC TC 57 WG13 and WG19 on the mapping of CIM measurements and IEC 61850 that is part of planned new editions of IEC 62361-102 and IEC 61970-301. The next edition of IEC 62746-4 should also refer to the same set of measurement type strings from IEC 61970. The list of variables is based on the typical values needed in control center applications, including the near real time data items described in IEEE 1547. The mapping of CIM-61850 for real time data includes data objects for the MMXU measurement logical node and the MMTR metering data logical node.
There is a lot of interest now in energy flexibility from customer installations. One of the challenges is that there are many communication protocols and data models defined by various groups with different perspectives such as grid operators, aggregators, customer energy management systems, metering systems and controllable resources such as solar panels, EV charging and HVAC.
TC 57 WG21 is collaborating with other groups to produce a mapping document between the CIM based measurement type strings and other protocols. The first of these protocols is the mapping to the COSEM OBIS codes described in IEC 61850-80-4. This was then combined with the mappings between OBIS codes and CIM reading types defined in IEC 62056-6-9.
Electric vehicle charging is of interest to several IEC working groups, so the mapping document also includes a mapping to the Open Charge Point Protocol (IEC 63584). Managing energy demand is also of interest in industrial premises. These have their own SCADA protocols, but industrial automation is gradually adopting more comprehensive and secure protocols like OPC-UA. The draft mapping therefore also includes the identifying “browse names” defined in the OPC 34100 companion standard.
This mapping work has highlighted a few issues such as the use of the term “real energy” by IEC 61850, whereas the metering standards all use the term “active energy”. Future editions of IEC 61850 will probably align more of this terminology.
Biography:
Tom Berry studied Electrical Engineering at Bath University, UK. For the last 25 years he has worked for Schneider Electric in the UK and France.
Tom has worked on control center projects integrating SCADA systems within dispatch training simulators, transmission and distribution network management systems. He now works “closer to the edge” as a software architect for feeder automation RTUs. He is a member of several IEC TC57 WGs and the editor of IEC TS 62361-102 technical report on CIM-61850 harmonization.
