IEC 61850 - A BRAND NEW WORLD#4
One of the key advantages of IEC 61850 based systems is the availability of the Substation Configuration Language that allows interoperability and a seamless integration process. The SCL is basically a system specification of the substation equipment connections in a single line diagram. It also documents the allocation of Logical Nodes to devices and equipment of the single line to define functionality, access point connections, and sub network access paths for all possible clients. And finally, it defines the instantiated data model of the different IEDs including optionally preconfigured values for configuration parameters.
What is of specific interest for protection and control applications is that it allows the development of engineering tools for configuration, protection coordination and testing that use a common standard data format.
SCL based configuration process
The overall functionality of any IEC 61850 compliant device is available in a file that describes its capabilities. This file has the extension “ICD” meaning IED Capability Description. The system specification tool supplies to the system configuration tool information such as the single line diagram of the substation and the required logical nodes. The file extension for this file is “SSD” meaning System Specification Description.
The system configuration tool then provides information to the IED configuration tools regarding all IEDs, communication configuration and substation description sections. This information is in a file with the “SCD” extension meaning Substation Configuration Description. This information also needs to be provided to the other tools in order to allow them to configure the set of functions to be performed.
The Standard IED configuration tool sends information to the IED upon its instantiation within a SAS project. The communication section of the file contains the current address of the IED. The substation section related to this IED may be present and then shall have name values assigned according to the project specific names. This file has an extension of “CID” meaning Configured IED Description. Currently there is ongoing work to expand the content of this file to include all settings, thus providing the required configuration data for both the IED itself, and also for the different functional tools
IEC 61850 is the new communications standard that allows the development of a new range of protection and control applications that result in significant benefits compared to conventional hard wired solutions.
It supports interoperability between protective relays and control devices from different manufacturers in the substation which is a necessity in order to achieve substation level interlocking, protection and control functions and improve the efficiency of microprocessor based relays applications.
The modeling of IEC 61850 based multifunctional distance protective relays requires good understanding of their functional hierarchy, as well as the modeling principles defined in the standard.
Complex devices, such as transmission line protection relays are modeled as servers with multiple Logical Devices that correspond to typical substation functions, such as Protection, Measurements and Recording.
The model needs to properly represent the functional hierarchy of the protection relay and at the same time use the available model hierarchy defined in the standard.
High speed peer-to-peer communications between IEDs connected to the substation LAN based on exchange of GSE messages can successfully be used to replace hard-wiring for different protection and control applications such as the protection of distribution buses, distributed recording or load-shedding in substations with varying configuration.
Sampled Measured Values communicated from Merging Units to different protection and control devices connected to the substation Process bus replace the copper wiring between the instrument transformers in the substation yard and the IEDs.
Such systems provide some significant advantages over conventional protection and control systems used to perform the same functions in the substations:
Reduced wiring, installation, maintenance and commissioning costs
Easy adaptation to changing bus configuration in the substation
The Substation Configuration Language allows interoperability and a seamless integration process. The common substation or IED configuration files can be exchanged between different configuration, coordination, analysis or testing tools in a way that significantly improves the efficiency of the engineering process.