[b]1 Introduction[/b] I have previously published two articles in *Power System Technology*, namely "Seamless Communication System Architecture for Telecontrol" and "Introduction to IEC 61850," which introduced the IEC's determination to develop a unified seamless communication system network transmission protocol for power systems based on IEC 61850 (Substation Communication Networks and Systems), as well as the content and characteristics of IEC 61850. This protocol will certainly be adopted in my country after its publication. Data exchange between substations and control centers using dedicated communication lines should adopt IEC 60870-5-101. If some power systems need to use networks as a means of communication to exchange information, then from now until the publication of the seamless communication system network transmission protocol, there are several network transmission protocol options: ① IEC 60870-5-101 and IEC 60870-5-104; ② IEC 60870-6-TASE. 2; ③ DL/T476. Of the above options, the first option is undoubtedly the most suitable, because there are already many RTUs using IEC 60870-5-101, and with the addition of IEC 60870-5-104, network transmission is easier to implement, with less development work, lower price, and better performance, making it worthy of promotion (as introduced in reference [1]). Since the IEC 60870-6 (TASE.2) protocol is a protocol for exchanging information between dispatch centers, using TASE.2 as the network transmission protocol between RTUs and control centers does not meet performance requirements, and TASE.2 is relatively complex and expensive, making it unsuitable as a network transmission protocol between substations and control centers. One opinion suggests that TASE.2 used between substations and control centers can be simplified (called simple TASE.2), requiring only the use of the TASE.2 data (DATA), dataset (DATA-SET), transport set (TRANSFERSET) (corresponding to IEC 61850's REPORT-LOG), and device (corresponding to IEC 61850's CONTROL) model, i.e., using TASE. TASE. 2 is a subset of IEC 61850; another reason is that both TASE. 2 and IEC 61850-8-1 are mapped to MMS, making the transition to a seamless communication system architecture protocol easier. But what is the actual situation? What are the differences between TASE. 2 and IEC 61850-7/8-1? Is the transition from TASE. 2 to a seamless communication system architecture protocol easier? Will it require a complete overhaul? This article analyzes these questions. IEC will develop a seamless communication system architecture protocol based on IEC 61850, meaning substations and control centers will communicate via 61850 (Substation-Control Centre Communication via 61850, i.e., IEC 61850+). Currently, the specific content of IEC 61850+ cannot be accurately described; only a comparison between IEC 61850 and IEC 61850-6 (TASE. 2) can be made. This paper only analyzes and compares the three basic telemetry tasks and data models related to data collection (DATA, DATA-SET), event reporting (REPORT-LOG (TRANSFERSET)), and control (DE-VICE). [b]2 Comparison of TASE. 2 with IEC61850[/b] 2.1 Main differences in working principle (1) Differences in layering and corresponding services IEC60870-6 is designed for data exchange between control centers. It requires two control centers to establish databases and bilateral tables in advance, know what data and data attributes the other party has in advance, and obtain the values ​​of these data by calling the data name after startup. These data and attributes do not include plant and equipment attributes. They only have these attributes when connected to the network topology. It is point-oriented. The server in IEC61850 consists of several logical devices. A logical device consists of several logical nodes. A logical node contains several data. Data contains several data attributes. Data attributes have various data types, values, and functional constraints. IEC 61850 provides various services such as server directory, logical device directory, logical node directory, data directory, and read data definition (Figure 1). [img=320,252]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2001-10/2-1.jpg[/img] Through the server directory service, clients can obtain the names of each logical device on the server; by using the logical device directory service in sequence according to each logical device name, they can obtain the names of each logical node of the corresponding logical device; by using the logical node directory service in sequence according to each logical node name, they can obtain the names of each data node of the corresponding logical node; by using the data directory service in sequence according to each data name, they can obtain the names of each data attribute of the corresponding data; and by using the read data definition service, they can obtain all the data attribute definitions of the corresponding data. Immediately after power-on, in online mode, clients can use these services to create a mirror image of all the other party's data in the client's database. These services are used to retrieve the definitions of the entire hierarchy within the device, the definitions of all accessible information, and the definitions of all class instances. During normal operation, these services can be used to monitor changes and operational status of various servers, enabling configuration management. To achieve this functionality, the device must be self-describing. IEC 61850 specifies the use of a self-describing method. IEC 61850-7-3 and -7-4 provide over 80 logical node classes and their names, over 350 data classes and their names, and 23 common data classes, and define a set of data code composition methods. Figure 2 shows an example of object naming. In the figure, XCBR1 represents the circuit breaker logical node name, Mode represents the data name of some attributes representing the overall status of XCBR, and stVal represents the data attribute name (status value). [img=299,217]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2001-10/2-2.jpg[/img] In Figure 2, MyLD is the logical device name, MyLD/XCBR1 is the logical node code, and MyLD/XCBR1... Mode is the data code, and MyLD/XCBR1. Mode. stVal is the data attribute code. From the above description, we can see that although IEC61850-8-1 and TASE.2 both use MMS, their principles are different and they cannot be compatible in implementation. When querying the device using TASE.2 with the server directory, logical device directory, and logical node directory, no answer can be obtained, and the expected function cannot be achieved. The new technologies such as object-oriented, device-oriented, and self-describing adopted by IEC61850 are in line with the trend of technological development. The application of these new technologies will promote the development of SCADA system and configuration management technology, and develop the current data acquisition, monitoring and control functions towards data management. (3) Differences in control process Figure 3 is a schematic diagram of the control process of TASE.2. [img=333,206]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2001-10/2-3.jpg[/img] Control is a selection/execution process. TASE. Control method 2: The client selects the object to be controlled using the read service. The server verifies the CheckBackID of <Device-Name>-SBO. If access is allowed, it responds and changes its internal state to ARMED (ready state). The client then sends an operation command (Figure 3) to complete the selection/operation process. Clearly, this control process cannot implement feedback verification because the selection service uses a read service. IEC 61850 has a control process similar to the one described in TASE. 2, but it also defines other control processes, such as a write service for the selection service. After receiving the request, the server responds with a write response PDU. This MMS write response PDU only contains whether the write request service was correctly received; it does not contain feedback verification information. The server generates a verification code through hardware and sends it to the client via the InformationReport service. The client compares the selection information of the sent command with the feedback information from the InformationReport service to determine whether to send the operation execution command, thus truly realizing SBO (Select-Based Operation with Feedback Verification). See Figure 4. [img=300,223]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2001-10/3-1.jpg[/img] As can be seen above, the control processes of IEC 61850-7-2 and -8-1 meet the requirements of power systems for control (circuit breakers, transformer taps, relay protection settings, etc.) and have true feedback verification. ACSI (Abstract Communication Service Interface) is mapped to MMS. Since MMS does not have a suitable PDU, the InformationReport service is used to transmit verification information. The InformationReport service is an unacknowledged service. The entire process includes write request/write response, unacknowledged service, and operation execution. Although the process is slightly more complex, it can truly achieve feedback verification. TASE. 2 and IEC 61850-7-2 and -8-1 have completely different control processes and use completely different MMSPDUs, making them incompatible. (3) Difference between Reporting and Recording Transmission Processes: When an event occurs on the server, according to IEC 61850-7-2 (see Figure 5), the recording processor of the recording module immediately records the event. Once the server is associated with the local master station, the reporting processor of the reporting module immediately reports to the client using the InformationReport service, thus speeding up event transmission. Since the InformationReport service is an unacknowledged service, the server cannot know for sure whether the client has received the data transmitted by the InformationReport service. IEC 61850-7-2, 8-1 also stipulates that the client can use the ReadJournal service to read records from the records by time period or item segment. The ReadJournal service is a request/response service, and its transmission reliability is higher than that of the unacknowledged InformationReport service, ensuring no event loss. After receiving the InformationReport, the client can also send an AckReport for confirmation. [img=500,116]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2001-10/3-2.jpg[/img] [img=500,153]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2001-10/3-3.jpg[/img] According to TASE. 2 (Figure 6), the transmission reports for the four types of transfer sets (i.e., dataset transfer sets, time series transfer sets, transfer account transfer sets, and information message transfer sets) all use only the unacknowledged InformationReport service of MMS. [img=300,195]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2001-10/4-1.jpg[/img] The report transmission processes of TASE. 2 and IEC 61850 are different, and the MMSPDUs they use are also different, making them incompatible. TASE. 2 only uses the unacknowledged Information-Report service of MMS, while IEC 61850 uses the unacknowledged Information-Report service and Read Journal service of MMS. The reliability of event reporting and transmission records in IEC 61850 is higher than that of related functional data transmission in TASE. 2. 2.2 TASE. 2 and IEC 61850 services of the same nature are mapped to the same MMS PDU (MMS Protocol Data Unit), but the options and functions differ. IEC 61850 defines Get Data Value and Set Data Value services for the DATA model 2, and also defines GetDataValues ​​and SetDataValues ​​services. The difference lies in that these two services read and write data, both mapped to MMS-PDU Read and Write, but their functions differ depending on the MMS-PDU Read and Write options. IEC 61850 only allows reading and writing data with a single data name once, therefore it specifies that only the VariableSpecification enumeration table (VariableListName) can be used. In contrast, IEC 61850 allows selection of one or more of the following selectors at a time: Data Reference, Data Attribute Reference, and Data Code. Functional constraints (Data-Reference.FunctionalConstraint), logical node code.FunctionalConstraint (LNRef.FunctionalConstraint), and IEC 61850 selectors, except for the DataAttribute-Reference selector which can only read/write one value at a time, can all read/write multiple data attributes. IEC 61850 selectors have more types and are more flexible and convenient than TASE.2. For example, according to the functional constraint, one can choose to read real-time information and refresh the database, or select the functional constraint as configuration to collect configuration information of logical devices and logical nodes, realizing online configuration management of system equipment. It can collect the operation status of IEC, and also understand the operation status and parameters of primary equipment in the power system. In addition to data acquisition, IEC 61850 also expands its functions to include data management and configuration management. It can use browser technology in the power system to perform online monitoring and management of primary and secondary equipment. Because of the wide bandwidth of the network, more functions can be realized. Similar situations also occur in the following services: GetDataDirectory (corresponding to the read data value name in TASE.2 (GetDataValue)). The functions `Names`, `GetDataSetValues` (corresponding to `Get Data Set Element Values` in TASE.2), and `SetDataSetValues` (corresponding to `Set Data Set Element Values` in TASE.2) are used. TASE.2 and IEC 61850 map services of the same nature to the same MMS PDU, but their options and functions differ and they are incompatible. 2.3 The data models defined by TASE.2 and IEC 61850 differ significantly. A unified data model is an important aspect of achieving a seamless communication system, namely, implementing a Common Information Model (CIM). For SCADA/EMS, a unified real-time data model reduces the format conversion of gateways and data objects. TASE.2, having been published and widely adopted, can only be interfaced with CIM using adapters. IEC 61850 is under development and is coordinating with the CIM of the under-development IEC 61970 (EMS/SCADA Application Program Interface) to achieve a unified CIM. 3 In conclusion, IEC 61850-7, -8-1 is based on UCA 2.0. IEC 61850-7, building upon UCA 2.0, adopts new technologies such as self-describing, object-oriented and device-oriented programming, layering, and abstract communication service interfaces. This paper only analyzes three aspects of basic telemetry tasks (i.e., data collection, event reporting, and control). From the above analysis, it is clear that IEC 60870-6 (TASE.2) and IEC 61850-7, -8-1 differ to varying degrees in their working principles and in the PDUs mapped to the MMS, or in the selection and functions of the PDUs. Therefore, an RTU programmed according to the TASE.2 international standard cannot be identical to one programmed according to IEC 61850. The connection between the master station developed in -7-2 and -8-1 is similar to the connection between TASE.2 and the local master station of the substation developed according to the IEC61850 protocol when TASE.2 is used in the bay layer of the substation. TASE.2 and the IEC61850+ interface to be developed in the future will also have similar problems. At present, the development of the communication protocol between the substation and the control center according to the TASE.2 protocol can only be said to be a technical training preparation for the development of the program according to the IEC61850+ protocol in the future. When the control center is implemented according to the IEC61850+ protocol, the communication protocol implemented by the substation according to TASE.2 may have to be changed to the IEC61850+ protocol to connect with the control center. For the main reason for using the substation-control center communication through IEC61850 (61850+) as a seamless communication system protocol, please refer to the literature. [b]References[/b] ［1］Tan Wenshu. Introduction to the IEC61850 protocol for substation communication networks and systems［J］. Power Grid Technology, 2001, 25（9）.