Transformer Inspection Robot: ABB TXplore in the Oil

A large power transformer is a steel tank full of mineral oil, and when something goes wrong inside it, somebody has to look. For decades that meant draining the oil and sending a trained inspector in through a manhole. A transformer inspection robot does the looking while the oil stays in the tank. ABB built one called TXplore, a small submersible introduced in 2018 that now belongs to Hitachi Energy. This post covers the hand inspections, how TXplore was developed, what drones, AI software and legged robots are doing on the grid this month, and where ABB robots could fit.

A technician lowers ABB's TXplore robot through a manhole into an oil-filled transformer. Photo: ABB

How transformer inspections meant draining the oil

Oil does two jobs in a power transformer: it insulates the windings and carries away their heat. Utilities still need to look inside now and then, for example after a lightning strike, to find the exact place and severity of a fault, or before a planned repair. ABB's 2018 description of the old routine reads like a small construction project. The oil had to be pumped out and stored, so tanker trucks, processing rigs and vacuum filling equipment came to the site. Then a highly skilled inspector climbed into the tank with a medical team standing by. The transformer was usually out of service for three days, and the inspector and the windings were both at risk.

A transformer at TVA's Chickamauga Dam near Chattanooga, Tennessee, in June 1942. Photo: Alfred T. Palmer / Library of Congress via Wikimedia Commons (public domain)

The first way around this was to test the oil. As insulation and oil break down they give off gases, and those gases dissolve in the oil. Engineers were already discussing how to collect and analyse them in 1928. In dissolved gas analysis, a technician draws oil into a gas-tight glass tube or syringe and sends it to a laboratory gas chromatograph. There are mobile analysers now too, and sensors that stay on the transformer and report its condition, such as Hitachi Energy's TXpert range. All of this narrows things down, but ABB noted in 2018 that utilities still needed internal inspections to pin down where a fault was and how bad it was.

An electric arc between test electrodes during a transformer oil breakdown test. Photo: HVWeb / Wikimedia Commons (public domain)

ABB proposed a robot for the job in late 2012. A team with researchers at its US research center in Bloomfield, Connecticut, and transformer engineers in St. Louis designed a remotely driven submersible that would not harm the oil. Prototypes spent more than 96 hours in leak tests, were driven in seven oil-filled tanks and were checked for oil contamination and for gas bubbles from the propellers. In 2016 it inspected production transformers at the St. Louis factory. American Electric Power watched a demonstration in March 2017 and that summer let ABB inspect one of its transformers, more than 50 years old, without handling any oil. TXplore was launched at the Hannover trade fair in 2018.

TXplore during a demonstration inside an oil-filled tank. Photo: ABB

Submersibles, drones and AI on today's grid

In July 2020 ABB sold 80.1 percent of its Power Grids division to Hitachi. The business was renamed Hitachi Energy in October 2021, and Hitachi bought the remaining shares in December 2022. TXplore went with it. A 2020 webinar on Hitachi Energy's website lists a trained TXplore operator in Qatar among its speakers. The robot has no tether. Propellers and buoyancy control move it through the oil while lights and cameras record the bushings, leads, tap changer and core. Once the transformer is prepared, two people do the work, a technician on top of the tank and a pilot who drives the robot. ABB said an inspection takes less than a day, against three or more days for a human one.

TXplore navigating inside an oil-filled transformer. Photo: ABB

The pictures can change a diagnosis. In one pilot a customer suspected its tap changer, but TXplore's camera showed that the failure was between two disks of a winding, and the images can be shared with experts anywhere in near real time. Small transformers on poles are checked from the outside, and there the camera is moving into the air. On 21 October 2026 Team UAV said it had photographed 500 pole-mounted transformers in Cornwall, Wales and the Midlands for National Grid Electricity Distribution (NGED). Softwire is building computer vision models that look for corrosion and other visible wear in the pictures, in a project funded through the Network Innovation Allowance.

A pole-mounted transformer on a power line near Caistor, England, 2025. Photo: Pete Cruse / Wikimedia Commons (CC BY-SA 2.0)

TXplore left ABB with the grid business, but ABB's industrial arms already work in transformer plants. In September 2026 ABB described an automatic core stacking cell at Changzhou Sieyuan Toshiba Transformer in China, where IRB 6740 robots stack 60,000 silicon steel laminations up to 4.5 metres long to a tolerance of 0.5 mm. Our post on transformer manufacturing covers that job. ABB designed and simulated the whole process in RobotStudio, which it says cut commissioning time on site. Using an arm for inspection is only a possibility so far, and nobody has announced such a project. An arm that places laminations could also carry a camera over a finished core and its windings before the tank is closed and filled.

ABB IRB 6740 robots with vacuum grippers stacking transformer core laminations at Sieyuan Toshiba in Changzhou, China. Photo: ABB

Where transformer inspection robots go next

Robots are also starting to inspect equipment that stays live. In an opinion piece published on 22 October 2026, Daniela Shchegelskaya of Elimpus described adapting Boston Dynamics' Spot to carry partial discharge monitoring equipment through live power substations, in an ongoing proof of concept. She lists the limits plainly: some instruments still have to be calibrated by hand on site, radio links drop, batteries run out, and once she had to take over when the robot picked a route toward sensitive construction work. On 1 October ANYbotics launched Shift, software that schedules fleets of its ANYmal robots and turns their thermal, acoustic, visual and gas readings into maintenance work orders.

ANYmal D walking through a substation on a visual, thermal and acoustic inspection round, 2021. Photo: Cvoellmy / Wikimedia Commons (CC BY-SA 4.0)

NGED says pole-mounted transformers carry power to homes and businesses, particularly in rural communities, and it hopes AI will help it spot problems earlier and plan maintenance better. A factory that runs its own large transformer would feel the 2018 numbers more directly, since ABB said robotic inspection usually cuts the downtime to under a day. ABB also planned to connect TXplore to its ABB Ability digital platform, and Hitachi Energy now markets HMAX Energy, an AI-powered service suite for critical energy infrastructure. My guess is that more of the inspection will move into software, with robots and drones collecting the data. For robots that work on overhead lines, see our power line robot post.

A large power transformer in a substation with a worker on a lift near its top, from ABB's 2018 TXplore article. Photo: ABB

A submersible still needs the transformer switched off and prepared, and it only fits units large enough to take it, so the outage and its cost do not disappear. The robot must also leave no chemical or physical trace in the oil, which is why ABB tested for contamination and propeller bubbles before launch, and robots in live substations still need a person ready to take over. Then there are skills. TXplore needs a trained pilot, and Shchegelskaya argues that engineers must know exactly what a remote inspection did not cover. NGED expects the first phase of its AI project to finish by the end of 2026.

A robot pilot at a laptop beside ABB transformers during a TXplore inspection in a factory hall. Photo: ABB

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