A Simulation Model for IEC 61850 Representation of Switchgear in the RTDS Simulator
In IEC 61850 based Substation Automation Systems (SASs), switchgear control systems can be tested conveniently using software tools. Such testing often requires simulation of the entire electrical substation and accurate representation of switchgear using IEC 61850 data models. Typically, it is required to model switchgear in the substation inside the simulation case and have them interfaced with control functions of external Intelligent Electronic Devices (IEDs). Therefore, representing switchgear and their associated controls using standard data models is a key feature that an IEC 61850 test tool should possess. Our latest IEC 61850-GSE implementation, GTNETx2-GSE-v6 component, comes with switchgear simulation capabilities and together with other advanced features of the RTDS Simulator, provides means to conveniently test advanced IEC 61850 based SASs.
The simulation model developed in GTNETx2-GSE-v6 for switchgear representation is primarily based on an entity called a switch object, which is a combination of three Logical Node (LN) instances, one each from LN classes XCBR (or XSWI), CSWI and CILO as shown in Figure 1. The XCBR LN instance (representing a circuit breaker) resides in the process level and CSWI and CILO LN instances (representing, respectively the switch controller and the interlocking functions of that beaker) are in bay level. Information flow between these LN instances is internal to the model. A particular switch object can be mapped to a desired circuit switch in the simulation for control operations. The CILO LN instance typically takes external inputs to determine the status of the interlock. A remote client can access the switch object for monitoring and control purposes using the Manufacturing Message Specification (MMS) protocol. The simulation model can also exchange information such as circuit breaker statuses (published as GOOSE messages) and trip signals (subscribed as GOOSE messages via Generic Inputs) with external IEDs independently from the switch controlling function.
Switch objects are created as a part of configuring the data model of the GTNETx2-GSE-v6 component, using its IED configurator tool, the SCD Editor. The switch object supports all four standard control model types (direct control with normal security, Select Before Operate (SBO) control with normal security, direct control with enhanced security and SBO control with enhanced security ) with an additional and non-controllable “status-only” option. Control model type and type of the switch (XCBR or XSWI) is chosen when the switch objects are first created. All three LN instances (XCBR/XSWI, CSWI, CILO) of the switch object are created simultaneously in the data model and remain locally interlinked. Switch objects with all of their related LN instances exist in a dedicated Logical Device (LD) in the data model. Furthermore, the LD carrying the switch objects has a dataset each for MMS (reports) and GOOSE communication.
Notice that a switch object in the simulation exists independently from the circuit switch, control parameters and interlock inputs it is linked to, regardless of them originating from inside the simulation or elsewhere. This enables, for example, a switch object to be connected to an external circuit breaker and to other external inputs, if the user so wishes.
Operating switchgear in a substation can be done either locally (at the process level) with manual control or by a command from bay, station or remote level operators. Control authority designates an operator’s right to control a specific circuit switch and is used to grant accessibility to operators at different locations and to avoid conflicts between them. A prescribed set of control parameters as per IEC 61850 , determines where the control authority resides at a given point of time. The switch controller takes control inputs to determine the standing of control authority. Operation of a switch controller is only carried out in response to a command from an operator that holds the control authority for that switch object. Originator category (or orCat) indicates type/location of the operator that has sent the request to control the object.
Any correctly configured MMS client can connect to the GTNETx2-GSE-v6’s MMS server with the switch objects. The users have the option to use the MMS Voyageur, a standalone MMS client program available in RSCAD, for this task. The MMS Voyageur can test the connection setup with the server device, browse the data model of the server device, read and write server data and perform control operations. In addition, it has a capability to emulate different originator categories and command service types.
This short video demonstrates the operation of simulated switch objects with the MMS Voyageur. Please note that this video does not demonstrate all the features. Please review user guides of the GTNETx2-GSE-v6 and the MMS Voyageur for more information.
Each GTNETx2-GSE-v6 component (runs on one of two modules of the GTNETx2 hardware), can simulate up to 32 switch objects representing 32 circuit switches in the simulated system. Each switch object is configured, operated and monitored independently and all relevant control parameters are user configurable. Users can also take advantage of the MMS Voyageur’s runtime scripting capability to automate test procedures for switchgear control systems with numerous checks and switching operations.
Moreover, publishing of circuit breaker statuses (XCBR.Pos.stVal) as GOOSE messages enables users to interface with the circuit switches in the simulation more conveniently in substation protection related applications. Testing and verification of the electrical interlocks in the SAS is another advantage for the users. Overall, GTNETx2-GSE-v6 provides an accurate representation of circuit switches and their controls in an IEC 61850 based SAS for testing and validation, individually as well as a group.
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Authors: Dinesh Gurusinghe and Sachintha Kariyawasam, June 2018
 Communication networks and systems for power utility automation – Part 7-4: Basic communication structure – Compatible logical node classes and data object classes, IEC 61850-7-4, Ed. 2, Mar. 2010.