Modern Distribution Grid Technologies

Article By : Thorsten Platz, Hitachi ABB Power Grids 

The electric power landscape is rapidly evolving. Whether the challenge is finding mutually beneficial means to integrate bulk renewables, local DERs, or microgrids, digital substations and other smart grid technologies such as RTU-based ATS systems can provide power operators the edge needed to thrive...

Industries need continuous power supply to keep their processes running. Utilities work to ensure the highest possible supply availability to their customers. While in distribution, network operators need to comply with regulation codes to ensure a stable and available supply of electricity. In all instances, the manual control of redundant systems is complex and therefore subject to human errors and time consuming.

In order to better manage the ever complex demands these industries face, technologies focused on automation and communication are key to creating a self-healing grid that will protect asset intensive industries against power outages, ensure customer satisfaction, and support the integration of renewable energies into the grid in a stable and secure manner.

This is particularly critical as increased demand on the grid will pressure power operators to provide a reliable, uninterrupted supply of electricity. Looking toward the future, it is clear that the power systems industry will need to embed two key assets into the future development of the grid: flexibility and resilience.

Flexibility and Resilience

In 2018, the number of power interruptions in the U.S. hit a high of 5.8 hours of disruption per customer. As 2021 unfolds, flexibility will mean responding to unexpected situations such as weather disruptions and supply shifts more quickly. As such, while some essential measures to shore up the grid have required manual actions, leveraging technologies like automated transfer systems (ATS) and remote terminal units (RTU) help to support automatic decision-making.

Take for instance, the case of a leading power utility in Northern Hungary. With an automated distribution network that monitors and controls pole-top overhead line switches and secondary substations, they were able to uncover fault detection and directional information and speed up reaction times when interruptions occurred.

The need for our second asset, resilience, is best derived from the vulnerability of global supply chains observed during the Corona crisis. Of course, energy systems are also based on global supply chains, but in contrast to other industries, national policies are used to mitigate the risk of interruption of supply by local reserves. Countries stored gas, oil or coal for weeks or even months, and conversion of these energy carriers to electricity used to be local. But with the increasing dependency on geographically concentrated renewable energy this concept is changing. Future power systems will be more interconnected, and they will be operated closer to their limits – and by that be more vulnerable. And as there is no way to store wind, solar irradiation or also electricity in larger quantities, new concepts are required.

Resilience, i.e. the ability to ride through critical situations instead of focusing on avoiding them, therefore will become more important. This applies particularly wherever systems are becoming more complex and potentially vulnerable by more interconnection. As such, digitized systems will be more dependent on communication infrastructures. Resilience in this case would mean that they can still provide a base functionality in case these infrastructures are not available.

So how is all this possible?

The Key Technologies

The first step to a self-healing grid is an RTU-based automatic transfer system (ATS), which are particularly suited to avoid long interruptions in power supply at medium and low voltage and used in small industries, utilities, data centers, for transportation and in commercial and public buildings.

Specifically, the ATS function based on RTU hardware is designed for time delayed transfers in emergency lights, hazard ventilation, cooling systems, communication systems, and Alarm handling & monitoring to ensure continuous power supply in combination with a battery system or generator.

ATS Hitachi

One of the largest airports in Switzerland has experienced this system firsthand. The airport has several emergency power supply groups. The 16kV medium voltage (MV) network is divided into autonomous sectors. Each sector has an MV distribution station (so called terminal station) as well as several transformer stations. The transformer stations include a main connection to a terminal station with ring connection option among the transformer stations. This concept increases the power supply reliability in the buildings. Using RTUs, each sector of the airport’s MV power supply was controlled and monitored autonomously, which ensured that the millions of passengers, cargo and flights supported by the airport are always operational.

Here is an example of a fault detection isolation and restoration (FDIR) for an open ring configuration:

Hitachi - FDIR Configuration

The grids are transitioning to geographically distributed intelligence. Maintenance of so many devices with limited human resources presents a huge challenge for network operators. RTUs provide network operators with a secure interface for staying up to date and in control of all assets.

A major high-speed rail line, connecting the UK with mainland Europe is an example of what’s possible when all technologies work together. In order to ensure smooth operations, the high-speed rail line has multiple electrical substations along its line to ensure power flows to tracks at all times. The substations are connected via a SCADA software system that collects and interprets data from devices along the line. In addition, each substation is equipped with RTUs that carry out commands from the SCADA system to ensure the safe and reliable flow of electricity.

The electric power landscape is rapidly evolving. Whether the challenge is finding mutually beneficial means to integrate bulk renewables, local DERs, or microgrids, digital substations and other smart grid technologies such as RTU-based ATS systems can provide power operators the edge needed to thrive.

This article was originally published on EEWeb.

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