While implementing new technologies in power system, we should be able to use the past power system protocols and IEDs in its operation. Logical devices of IEC 61850 standard accommodate IEDs with existing past power system protocols. Logical devices of IEC 61850 standard are having logical nodes or LNs that are simpler function and are used to define complex IED functions. Data concentrator can be formed in a single device of a substation with IEC 61850 standard as it can support multiple logical devices.
IEC 61850 based networks use Ethernet or TCP/IP as their communication media. Copper wire communication media is being replaced with ethernet communication channels as it is less cost consuming and having higher speed of communication. IEC 61850 standards are also used as they have the characteristics of ‘self-description’ by which the substation devices can show its contents to several clients. In communication modelling IEC 61850 standard do support substation configuration model, client server communication model and peer to peer communication model [1].
Three operational levels of IEC 61850 communication architecture are shown in fig. 1. All the levels will perform some specific operations in a substation:
- Process Level- This level is having the communication between field devices and bay level IEDs. The substation field values will be measured with devices like instrument transformers, actuators and sensors and will be transferred to the bay level IEDs through process bus.
- Bay Level- This level is having IEDs to perform protection and controlling operations by receiving the substation primary inputs from the process bus communication level. In a single substation there can be various bays present with IEDs interconnected to each other.
- Station Level- At station level collection of bay data and implementation of controlling function will be done. From this level data can travel to other stations and also can send information to bay and process level of the substation.
Digital Substation with IEC 61850
The substation architecture of IEC 61850 enable station can be seen in fig. 2. In the diagram field data or input values of the substation will get collected using instrument transformers and sensors in the process bus level. Then the analog input data will get converted into IED readable format or in digital form while travelling through merging units that are placed inside control rooms or at field site of the substation. The digital form of field data will get transferred to the protection and control IEDs through Ethernet LAN or WAN networks [2].
Development of Multivendor Digital Substation
To obtain a better understanding and to perform interoperability testing of substation devices, a laboratory testbed has been designed in this study by taking devices from different vendors as shown in figure 3 and the hardware setup is shown in figure 4. The devices used in the laboratory setup are listed in table 1 with their respective operational configurations.
The prototype model configuration and interoperability testing require some software tools to be installed in the system. All software tools installed in this model are given in table 2 below.
Demonstration of Process Bus Communication Validation
- Testing GOOSE Communication
To test IED to IED GOOSE communications the breaker operation stages were configured in the form of gate logics in IEDs. Here, GOOSE communications were tested between the REL670 and REC670 IEDs. As GOOSE is a type of publisher-subscriber messaging, during the test REC670 was acting as a publisher IED and REL670 as a subscriber IED. Four gate logics were configured in the REC670 relay with corresponding breaker statuses, as listed in table 3 [3]. The ETE delay values of GOOSE messages travelling between the two IEDs were recorded during the test in the PCM600 disturbance recorder and are summarized in table 4.
- Testing SMV Communication
To test SMV communications, analog inputs from the field devices should travel through the process bus to the station IEDs. In this testbed, the omicron test kit is used to inject the analog inputs of the substation in the form of balanced voltage and current to the AMU.
The substation model implemented in this study had ratings of 220 kV and 1kA. The omicron was having settings of turns ratios for CT and PT inputs which were done using test universe software. With the turn ratio settings, the line values in the secondary of the omicron kit were: Vline=100V and Iline=1A [4]. The input values that were injected from the omicron secondary to the model are voltage and current phase values that can be calculated using equations (1) and (2) corresponding to the line values. The injected phase voltage and current values are given in table 5 and are calculated using equations (3) and (4).
where V_phase is the phase voltage, V_line is the line voltage, I_phase is the phase current and I_line is the line current.
The injected inputs will travel through the turns ratio meter (TRM) of the CT/ PT ports in the AMU and then get converted into digital signals or SMV messages. The TRM settings of the AMU were configured with the following turns ratios [5]:
CT turns ratio – 1000:1
PT turns ratio – 1:2200
The output result taken from the PCM 600 software installed in the PC is shown in fig. 12.
Conclusion
Basics of IEC 61850 standard and its implementation in a substation model to upgrade it into a Digital Substation model are presented in this chapter. Components of digital substation and unique behaviour of IEC-61850 protocol that makes a digital substation operation automated are also discussed.
A complete model of digital substation set up in laboratory has also been shown with all devices connected and commissioned as per the standard. The result analysis of the substation IEDs for process bus communications, GOOSE and SMV has been provided. The results show that a digital substation with IEC 61850 standards can be successfully used in the field of automated operations of substations.
References:
1. Patil, Mayur, S. R. Bhide, and S. S. Bhat. “Experimenting with IEC 61850 and GOOSE messaging.” In Power, Control & Embedded Systems (ICPCES), 2017 4th International Conference on, pp. 1-6. IEEE, 2017.
2. Lei, Hangtian, Chanan Singh, and Alex Sprintson. “Reliability modeling and analysis of IEC 61850 based substation protection systems.” IEEE Transactions on Smart Grid 5, no. 5 (2014): 2194-2202.
3. T. Bhattacharjee and M. Jamil, “GOOSE Publishing and Receiving Operations of IEC 61850 Enabled IEDs,” 2019 IEEE 1st International Conference on Energy, Systems and Information Processing (ICESIP), 2019, pp. 1-6, doi: 10.1109/ICESIP46348.2019.8938272.
4. Jamil, Majid, Mohammad Rizwan, Tanushree Bhattacharjee, and Abdul Azeem. “Digital Substations with the IEC 61850 Standard.” (2021): 41.https://doi.org/10.1063/9780735422827_004.
5. T. Bhattacharjee and M. Jamil “Real Time Operation of IEC 61850 based Digital Substation” International Journal of Engineering and Advanced Technology, vol. 9, issue-1, Oct. 2019. DOI:10.35940/ijeat. A9748.109119.
6. T. Bhattacharjee, M. Jamil, Majed A. Alotaibi, Hasmat Malik, and Mohammed E. Nassar. “Hardware Development and Interoperability Testing of a Multivendor-IEC-61850-Based Digital Substation.” Energies 15, no. 5 (2022): 1785.
Dr. Tanushree Bhattacharjee has completed her PhD in Power Systems from Jamia Millia Islamia, New Delhi in 2022. She has received her M.E. in power system from Indian Institute of Engineering Science and Technology, Shibpur in 2014. In 2009, she has received her B-Tech in Electrical Engineering from Kurukshetra University. Currently, she is working as a R&D Engineer at GRIDsentry pvt. Ltd. India. She has served as a project fellow in UGC SAP DRS-II project at Jamia Millia Islamia, New Delhi. Also, she has served as an Asst. Professor at DCE Gurgaon and MNIT Jaipur. She started her career as a lecturer at REMTECH Shamli. She has published 8 papers in her area of research and 3 book chapters. Her areas of interest are power systems, substation automation, IEC61850, Cybersecurity of substation, PV inverters, microgrids and optimization techniques.
Dr Majid Jamil is a Professor of Electrical Engineering at Department of Electrical Engineering, Faculty of Engineering & Technology, Jamia Millia Islamia, New Delhi since January 2010. He was Head of the Department of Electrical Engineering from 2014 to 2017. Dr. Jamil has also served as Assistant Professor at BITSPilani, Dubai Campus, U.A.E from 2003 to 2006. Dr. Jamil has published more than 180 research papers in SCI, SCOPUS and other refereed journals and conferences. 19 PhDs and forty seven M. Tech. Dissertation thesis have been awarded under the supervision of Dr. Jamil. He is the author of text book “Grid Integration of Solar Photovoltaic Systems, CRC Press, Taylor and Francis, USA and edited two books and wrote several book chapters.
