TXpand – Protecting the Power Grid

Challenge

Transformers are the muscles of the power grid, enabling electricity to be utilized efficiently and effectively. They perform this essential and demanding task constantly – 24/7 for decades, with virtually no downtime, while subjected to every stress and surge in the power system.

Transformers are incredibly reliable and robust, yet studies show that even these most dependable components can fail and in every 1000 service-years a catastrophic failure and fire is predicted1, 2. These failures can be dangerous and have a huge impact on the supply of power – so it is vital to mitigate even this unlikely risk.

This challenge is amplified further in HVDC bulk transmission systems, in which  several gigawatts of power capacity could be lost in the event of a failure.

Solution

In a collaboration with Canadian transmission system operator Hydro-Quebec, Hitachi ABB Power Grids developed a rupture-resistant transformer tank solution; TXpand.

Combining our knowledge, the two companies developed sophisticated computer models allowing vulnerable areas to be strengthened while simultaneously making previously rigid areas flexible. This allows the transformer to literally expand during a major internal failure, absorbing the energy and preventing or controlling a potential rupture.

This technology has been deployed in Canada for several years and verified with a full-scale test in 2018, demonstrating TXpand’s capability to resist an internal failure of 20 megajoules (MJ) – 20 times the energy contained in a stick of dynamite.

A similar test in late 2020, in Sweden,  implemented a specific toughened “turret” – the location at which the bushing attaches to the transformer tank – to address the special challenges of HVDC converter transformers.

The test was a spectacular demonstration of the potential consequences of the failure of a transformer without TXpand, in contrast with the test on the TXpand equipped transformer which remained completely intact – exactly as planned.

“This rupture-resistant transformer solution concept is simple, but implementing it on complex transformers, of up to hundreds of cubic meters in volume, requires detailed engineering,” said Markus Pettersson, Global Product Manager for HVDC Converter Transformers, Hitachi ABB Power Grids. “We drew on over a century of transformer design and manufacturing expertise to develop the sophisticated simulations behind this design, combined with unique capabilities to perform full-scale demonstrations in our testing centers and live-stream anywhere in the world.”

Impact 

In an ideal world, neither Hitachi ABB Power Grids nor transformer operators would see the impact of this solution. Transformers are designed to not to fail and system operators carefully manage their grids to avoid damage to their power equipment. Yet unexpected surges, lightning strikes or other unforeseen events can happen and so, therefore, can catastrophic failures.

A hypothetocal failure in the largest transmission systems, could mean the loss of several gigawatts of power – worth millions of dollars per day – and this would be only the beginning of the cost to society.

By utilizing the TXpand rupture-resistant solution; fire, oil leakage and damage to surrounding equipment could be avoided in the unlikely event of a failure. Thus, the resulting outage would be a small fraction of the time – a spare transformer could be in place within hours, as opposed to weeks of cleanup, repairs and maintenance.

Of course, finally, and most importantly, avoiding a rupture could save lives.

Please watch a video about the recent tests here:

1. CIGRE Technical Brochure 537, “Guide for Transformer Fire Safety Practices.”

2. https://www.tdworld.com/substations/article/20964130/risk-equals-probability-times-consequences