Efforts to achieve carbon neutrality by 2050 are driving advancements in next-generation power grids. Specifically, this includes lessening the environmental burden caused by power grid facilities, maximizing the capabilities of existing facilities to assist with decarbonization efforts, strengthening the foundation for a stable power supply to expand renewable energy coverage, enhancing power supply resilience against natural disasters, and making power system operations more sophisticated while pushing digitalization forward. Power grids consist of various devices and systems that supply and control electric power referred to as power transmission and distribution systems, and their role will become increasingly important as the backbone of next-generation power grids.

The Toshiba Group is contributing to next-generation power grids through the development of better power transmission and distribution systems.

TAKAO Shuhei / ONISHI Tomoya / SHIRAI Hideaki

Sulfur hexafluoride (SF₆) gas possesses high insulation performance and has been widely used as a high-voltage insulating medium for transmission and transformation equipment including gas-insulated switchgears (GIS). However, because of the extremely high global warming potential (GWP) value of SF₆ gas, reducing use of this gas has become an extremely important part in pursuing carbon neutrality. Developing equipment that does not make use of SF₆ gas has accelerated worldwide in recent years.

Toshiba Energy Systems & Solutions Corporation is developing a lineup of substation equipment using natural origin gas under the AEROXIA™ brand. This includes a 72/84 kV AEROXIA™ series GIS that uses synthetic air as a replacement for SF₆ gas for the first time, as well as a compact design to accommodate the increased demand for renovating existing GIS by improving the surface conditions of high-voltage conductors and optimizing the performance of arc-extinguishing earthing switches. The first 72/84 kV AEROXIA™ series GIS was installed at the TEPCO Power Grid, Inc. Fuchu Substation, which started operations in 2023 as the first GIS using a natural origin gas in-service in Japan.

NOGUCHI Naoki / ISHIKAWA Taku / UCHIDA Keisuke

Sulfur hexafluoride (SF₆) gas is widely used in gas-insulated transformers (GITs) because of its superior insulating and cooling performance. However, as SF₆ has 24,300 times higher global warming potential (GWP) of carbon dioxide (CO₂), workers are forced to abide by strict transformer handling procedures during maintenance, such as extracting SF₆ gas from the equipment, etc. From the viewpoint of achieving carbon neutrality, the need has arisen in recent years for transmission and distribution equipment, including GITs, to replace SF₆ gas with an appropriate gas possessing a lower environmental load and is easier to handle.

Toshiba Energy Systems & Solutions Corporation has developed both a 66 kV-20 MVA GIT and an on-load tap changer (LTC) using nitrogen (N₂) gas, which is an inert gas contained in natural origin gases, as a replacement for SF₆ gas, significantly contributing to reducing the environmental load, improving maintainability, and easier handling.

YAMASHITA Syunya / NOZAWA Tsuyoku

The introduction of natural ester oil-immersed transformers as an alternative to mineral oil, which has traditionally been used for electrical insulation, is picking up speed in recent years in line with efforts to achieve carbon neutrality. Demand is particularly strong for such transformers in power distribution equipment installed at indoor substations with fire safety requirements due to the fire point temperature of natural ester exceeding 300°C.

To meet market needs, Kitashiba Electric Co., Ltd. has developed a compact, lightweight rapeseed oil-immersed transformer for indoor substations by improving the tank structure of conventional oil-immersed transformers in consideration of various installation location constraints. To meet user
requirements for retrofilling aged oil-immersed transformers by replacing mineral oil with rapeseed oil, we have confirmed that required fire suppression systems can be simplified by identifying rapeseed oil characteristics, such as the amount of residual mineral oil, fire point temperature, etc.

ISHIGURO Takahiro

The movement to achieve carbon neutrality by 2050 has been gaining speed in line with the long-term vision of cross-regional network development proposed by the Organization for Cross-regional Coordination of Transmission Operators, Japan (OCCTO) in 2023. The vision details plans for multiple high-voltage DC (HVDC) link construction projects in Japan.

Toshiba Energy Systems & Solutions Corporation has developed Japan’s first voltage-sourced converter (VSC) for HVDC power transmission systems, featuring modular multilevel converters (MMCs) without AC filters or reactive power branches, which was delivered to Pole 1 of the New Hokkaido-Honshu HVDC Link in 2019. We have also been awarded a contract for a VSC at Pole 2 of the New Hokkaido-Honshu HVDC Link. Our expertise in developing VSCs contributes to ensuring a stable electricity supply and expansion of renewable energy.

GOTO Shigehiko

Surge arresters play a critical role in the prevention of blackouts caused by natural disasters including lightning, and in suppressing various overvoltage and overcurrent conditions caused by transmission system operations. There is currently a trend in using polymer-housed surge arresters with polymer materials for housing.

Toshiba Energy Systems & Solutions Corporation has developed and commercialized a new lineup of polymer-housed surge arresters for 66 kV to 500 kV systems which is compliant with the latest standards for surge arresters specified in Japanese Electrotechnical Committee (JEC)-2374:2020 and the seismic design guidelines specified in the Japan Electric Association Guide (JEAG) 5003-2019. The new models are significantly more compact and lightweight compared with previous porcelain-type surge arresters thanks to a direct molding process to attach silicone rubber directly to electric elements including a zinc oxide element inside the surge arrester. We have also developed a 500 kV high energy type surge arrester offering greatly improved energy resistance as a countermeasure against accidents involving gas circuit breakers caused by direct multiple lightning strikes.

OHNARI Takaaki / SHIMOO Takahiro / UEDA Takashi

In recent years, the expansion of data centers associated with the explosive growth of generative artificial intelligence (AI) has given rise to the need for higher power transmission capacity. Because construction of new facilities for this purpose entails considerable time and cost, application of dynamic line rating (DLR) technologies is attracting attention, as they can accommodate a wide variety of environmental conditions at existing facilities by changing the power transmission capacity.

To make more effective use of existing facilities, Toshiba Energy Systems & Solutions Corporation is developing DLR technology to dynamically calculate transmission capacity limits by identifying bottlenecks in transmission lines using meteorological forecasting and wind resource analysis taking into consideration the terrain without the use of sensors. Verification tests on estimating wind conditions with the goal of practical application of the DLR technology confirm that predicted wind conditions generally agree with actual trends.

HOSHINO Tomohiro / INUZUKA Naoya

Expectations have traditionally been focused on transforming renewable energy into the predominant source of power to achieve carbon neutrality. Introducing more renewable energy systems, however, tends to hinder the stability of power grids due to a limited number of synchronous generators with system inertia and synchronizing torque, as typified by thermal power generation systems.

To rectify this problem, Toshiba Energy Systems & Solutions Corporation has developed the following new systems for special protection systems to maintain power grid stability by shedding the generators and loads in the event of problems: (1) a voltage stabilization system using artificial intelligence (AI) to control and maintain grid voltages within the appropriate level during normal grid operations with increasing difficulty, and (2) a resilience enhancing system to maintain rotor angle stability in case of coincident failures occurring in four-circuit bulk power transmission lines, as well as to maintain frequency stability when renewable energy systems are separated from the power grid. Special protection systems incorporating these systems can also increase the total transmission capability during normal grid operations, contributing to the mass introduction of renewable energy sources.

MIZUTANI Ryota / TOYOSHIMA Ichiro / TATEKOJI Takashi

To ensure stable power grid operation, several tens of or hundreds of thousands of outage tasks necessary for suspending equipment, such as inspections, repairs, expansions, etc., are performed annually by each power distribution and transmission company in Japan. Coordination of outage task schedules is currently handled by a limited number of engineers with a high level of operational knowledge and experience. However, an increasing number of aging facilities, complicated grid operations due to mass introduction of renewable energy systems, and changes in business configurations due to promoting workstyle reforms, have become issues of vital importance.

Toshiba Energy Systems & Solutions Corporation is developing an outage task support system applying a new workflow to streamline coordination processes using expertise gained during the development of grid control systems. Verification tests applying a prototype to a power distribution and transmission company’s actual grid have confirmed the effectiveness of its basic functionality.

NAGATA Shinichi / YAMAGUCHI Akihiro / SAITO Akito

With the progress of Internet of Things (IoT) related technologies in the field of substation equipment, large volumes of data from various sensors attached to equipment, including gas-insulated switchgear and transformers, can now be collected and analyzed to improve economic efficiency and maintainability. To make effective use of these data for early detection of signs of abnormalities and to rapidly recover from equipment faults, highly reliable, high-sensitivity diagnostic technologies have become essential.

The Toshiba Group has developed the following abnormality diagnostic technologies using proprietary artificial intelligence (AI): (1) technology to detect abnormalities based on time-series variations in waveform data by learning only normal operation data from the equipment, and (2) technology to identify the location of abnormalities using a target equipment 1DCAE model. We have confirmed the effectiveness of the basic functionalities.

KUROSE Yuta / HIROKAWA Ayumi

The latest digital technologies are being introduced into substation renovation projects and new constructions to optimize facility configurations and minimize the number of cables. In line with this, connection of protection and control systems to digital substations is replacing conventional metal cables with local area network (LAN) cables for data transmission.

In response to the requirements of multiple power companies, Toshiba Energy Systems & Solutions Corporation develops, tests, and provides various types of protection and control system equipment for digital substations compliant with the International Electrotechnical Commission (IEC) 61850 standard series. We are also working on the following new functions that take advantage of digital substation features: (1) failure detection and factor analysis using a wide variety of accumulated data, and (2) automatic recovery in the event of problems with the equipment.

Feature Articles

FUKUSHIMA Daishi / TAMURA Yuji / ZHANG Hao / KAWAMURA Wataru

The ongoing introduction of renewable energy systems and increasing demand for new electricity necessitates adequate measures to maintain the stability of electric power systems. Static synchronous compensators (STATCOMs), which can supply stepless variable reactive power at high speeds, have become essential for this purpose.

Toshiba Energy Systems & Solutions Corporation has developed a new STATCOM using modular multilevel converter (MMC) topology, which was delivered to the Shikoku Electric Power Transmission & Distribution Co., Inc. Nakamura Substation. By applying a delta open transformer for saving space, the new STATCOM main circuit equipment has a 50% smaller installation footprint compared to conventional STATCOMs using a buffer reactor. We have also included a power system stabilizer (PSS) to ensure electric power system stability, confirming its effectiveness via commissioning tests.

TANAKA Takahiro

With the growing interest in generative artificial intelligence (AI), a trend toward introducing new services using generative AI in a broad range of applications is picking up speed worldwide. With a growing market, issues associated with generative AI, such as the spread of harmful content and misinformation, confidential information leaks, etc., are of serious concern.

Toshiba Corporation has developed the following technologies to substantially improve the reliability of applications using generative AI services: (1) multiple guardrails to protect users from inadequate information by monitoring generative AI input-output information, and (2) technology to improve the accuracy of retrieval-augmented generation (RAG) via knowledge searches using internal documents, etc. in addition to existing large language models (LLM).

Frontiers of Research & Development

Method with Simple Loss Function Reducing False Positives to Predict Number of New Objects in Images for Few-Shot Object Counting Technology

*Company, product, and service names appearing in each paper include those that are trademarks or registered trademarks of their respective companies.

Vol. 80, No. 3, May 2025

Index