Relay protection
Smart grid and digital substation

Smart grid and digital substation

Software, data communication and control, etc, is standard in modern substations. Though the development and implementation of IEC 61850 since mid 2000’s, the way to design, configure and run the substations have changed. This IT influence brings many advantages but also introduce new challenges to the industry.

This chapter falls under the name digital substation. The digital substation have many different sub categories where the latest addition, the digital twin, have seen the dawn and enables virtual relay testing. If narrowed down to the everyday work for substation test engineers it mainly come down to IEC 61850 with its abstract data models defined can be mapped to several protocols. Current mappings are to MMS (Manufacturing Message Specification), GOOSE (Generic Object Oriented System Event), SMV (Sampled Measured Values).

Digital twin enables virtual relay testing

Simulating physical or functional performance in a computer - a digital twin - delivers benefits that include reduced costs, increased reliability, and better efficiency. Megger is the first substation testing company entering this area with the SMRT digital twin in IED protection schemes, and has enabled business to continue carrying out a range of tasks despite the travel bans and social distancing measures that have arisen during the COVID pandemic.

Virtual commissioning

Tests performed virtually with the SMRT digital twin removes errors and uncertainties upfront before entering the often time pressured commissioning phase. A small subset of those tests would have to be repeated in the real world to verify physical connections and that correct settings are loaded into the relays. There are many other areas beside commissioning where benefits are seen such as FAT, training, support, development to mention a few. Read more in detail in the digital twin article and the IEEE paper on the same topic.

IEC 61850 GOOSE interoperability

Interoperability is a property of a product or system, whose interfaces are completely understood, to work with other products or systems, present or future, without any restricted access or implementation. The interoperability requirement of the IEC 61850 standard has beneficially increased the “interoperability among different engineers” working for companies that are formally in competition. With field experience of IEC 61850 GOOSE communication in protection and control applications, it is possible today to list the main reasons for interoperability problems for multi- and single-vendor systems; however, the list of causes of interoperability failures would be longer than what indicated in this document, especially if considering the cases found during the beginning of the use of GOOSE messages.

Lessons learned from a 400 kV busbar misoperation utilizing the IEC 61850 standard

The implementation of IEC 61850 standard for substation design and commissioning is fast-phased method of defining grid protection schemes throughout the world.  The protection logic that involves dc control circuits are executed internally in the Intelligent Electronic Devices (IEDs) and effectively communicated between the IEDs via GOOSE. Any error in the mapping of GOOSE signals will result in undesired operation of the protection schemes.

Megger was involved with this case study where an investigation of the tripping of a 400 kV substation due to improper operation of a bus-bar protection scheme was in focus. This incident happened when a Zone 2 fault occurred on one of the 400 kV line feeders, immediately triggering a breaker-failure condition caused by an incorrect mapping od the Breaker-Failure Initiate (BFI) signal to bus-bar IEDs. This minor error caused the entire substation to be out of service. This paper discusses the methods of testing so that would help prevent this situation.

Megger solutions for IEC 61850

The relay test systems FREJA and SMRT together with the software MGC. Megger GOOOSE Configurator, are tools used to test and troubleshoot IEC 61850 communication, both GOOSE and process bus. Features like IEC 61850 sniffer, merge and compare, are cyber secure solutions that saves time and increase quality. Read more about Megger test solutions here.