Protocol
The IEC 61850 is a general transmission protocol for protective and control equipment in medium and high voltage electrical substations. Physically this communication is based on the Ethernet Technology. At present the Server-Client-communication over MMS (Manufacturing Message Specification) and TCP/IP (Transmission Control Protocol/ Internet Protocol) is supported. The communication stack for the Server which is developed by Beckhoff (see graphic below) is integrated step-by-step into the TwinCAT PLC in form of libraries. In the following graphic you can also see the IEC 61400-25 which has been defined especially for the Wind turbines and therefore is a specialization of the IEC 61850.
The most important libraries which are responsible for the mapping of the IEC 61850 will be described here:
Library | Description |
|---|---|
TcACSI.Lib | This library is responsible for a clean interface to the subordinate layers. The therefore realized "Abstract Communication Service Interface" contains all basic-data types of the above named standards and the corresponding blocks to browse through the hierarchical structures of the IEC 61850 or IEC 61400-25. This ACSI-interface allows a universal and future-proofed connection of the norm to the subordinated protocols. |
TcMMS.Lib | In the TcMMS.Lib the necessary services for the communication have been implemented. |
TcASN1.Lib | In this library the user has all of the coding- and decoding function blocks for the in BER (Basic Encoding Rules for ASN.1) coded telegrams. |
To realize the TCP/IP communication the TwinCAT TCP/IP Connection Server is used underneath the known libraries. This Supplement product is responsible for the realization of one or more TCP/IP-Server/-Clients in the TwinCAT PLC.
The in 2004 released IEC 61850 is strictly object-oriented and its data model is build up hierarchically. There are 5 hierarchical levels which have been implemented into the TwinCAT PLC through the corresponding libraries of the standards. Explanations and examples how to apply such a structure are defined under Protocol Overview.
Example of use
In this case the IEC 61400-25 allows that wind turbines from different manufacturers can communicate with a central control station. Because of the standardization the expectations are that manufacturer-specific protocols will be avoided. The company Beckhoff supports this way by the implementation of IEC 61850 and IEC 61400-25 into the TwinCAT Automationsuite.
