New Engineering Challenges In The Digital Substations

The continued expansion of digitalization in the substation protection and control has brought in a wave of improvements; especially when it comes to installation, commissioning, and pre-acceptance testing. As usual, it has also brought a new set of challenges, most of them related to the digitalization of the primary values coming from various sensors and sources, matching the hardware to the protocols’ requirements, and identifying and mitigating possible problem scenarios. Completing multiple steps of protection, logic, communication, and coordination are keys to success. This paper offers an in-depth view on the following aspects of substation automation engineering: • the effect of mixed merging units and non-conventional instrument transformers on different types of protection functions: in general, all the functions residing in the relays nowadays were developed with the idea that they will be using the analogue values from the system, digitized by their own A/D converters. How are they coping with values digitized by different devices, with different dynamic (and even static, sometimes) behavior? • is the IEC 61850 standard covering absolutely all scenarios or are there aspects left for interpretation that are undermining a smooth integration of different devices? • what’s the minimum set of requirements for wired communication devices (switches, for example) that will ensure their proper operation in all possible scenarios, including redundancy, priorities, time synchronization, etc. • could wireless devices be entrusted with ensuring an inter-station communication backbone for all kind of signals (including time-critical ones) or only for certain type of signals? • how the necessary bandwidth is calculated for a station-wide application (busbar protection, for example); which are the culprits that could undermine the calculated bandwidth in specific scenarios? • what types of interoperability tests need to be done prior to engineering phase, for example, ensuring that information files from different vendors can be properly understood and used by other equipment vendors. • how can the IEC 61850 system engineering complexities be minimized, what tools should be used for implementation and documentation? Are vendor tools good enough? Do we need an additional tool for system-wide configuration? Configuration files are essential but may not always integrate seamlessly with other vendor tools. • IEC 61850 follows a model-driven approach, it is providing a standardized way of representing and exchanging data within substation automation system, but what is the utility’s expectation? Does vendor defined naming convention meet utility’s requirements? • Digitization in substation provides a wide range of real-time data not only for operation but also useful for maintenance, how can operator utilize that information and improve the operation cost and efficiency.

These aspects will be discussed for all the different phases of engineering: concept, design, detail design, testing (including proof-of-concept testing), installation and commissioning. Also – documentation – as it is the fundament for all activities related to the substation automation engineering process.

This paper’s purpose is to take a holistic view upon the whole engineering process and provide tips and insights on best practices used today. Paper content is based on learnings from the deployed projects in North America and around the world.