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Between December 18-19, an unprecedented five Eurostar trains failed in the Channel Tunnel. The widespread disruption interrupted holiday plans of nearly 100,000 travelers, and was a major embarrassment for the operator. The Governments of France and the UK set up an Independent Review panel, which has published some interesting findings.

As background, the report states:

The design of Eurostar power cars is based on other members of the TGV family, but the trains are more complex machines. They have the most powerful and sophisticated electrical systems of any TGV, but within a much smaller space than other TGVs. Given their small size (for compatibility with the British loading gauge) and low weight, they are the most powerful power cars in current use – much more so than TGV motor units, since two units pull 18 cars.

Contrary to perception of Eurostar being a TGV or TGV-derivative, the design of the Eurostar locomotive is globally unique. Major modifications were required to accommodate British loading gauge — proving once again that custom rolling stock invites unexpected problems.

As compounding factor, there is no redundancy in Eurostar trainsets. This is by design:

Because the Channel Tunnel safety committee wanted Eurostar sets to be divisible into two parts, the two motor units are independent and do not have a high-voltage connection like those of a traditional TGV. As a result, if one motor unit has no high-voltage power because its pantograph is not working, it cannot obtain this from the other pantograph, so its motors are unusable.

Another problem: test and debug procedures for the Eurostar design did not accurately model conditions in the tunnel. Instead, designers used the winterization measures from standard TGVs, which do not encounter anything like the 12km Channel Tunnel:

The environment in the Channel Tunnel is warm and humid. The temperature in the middle, 12 kilometres from either end, is around 25°C and the air, as well as being close to total saturation, is heavily loaded with suspended particles of concrete and metal dust from the brakes of trains using the Tunnel. In winter, trains suck in large quantities of very cold outside air, sometimes containing snow, before they enter the Tunnel, which cools all the structure and components. As the cold metal comes into contact with the warm, damp and dusty air inside the Tunnel, this causes condensation. The snow melts extremely quickly, saturating those parts of the power car which it has infiltrated and causing the electronic and other components to malfunction. The warmth, damp and dust also causes arcing and short circuits.

In addition to the 2009 failures, the “specific atmospheric conditions” of the tunnel have caused failures going back to 1996. In almost every winter, Eurostar had attempted various quick fixes to the on-going problem. The Independent Review recommends a “comprehensive overall review asking detailed questions about these recurring incidents and looking at radical ways of preventing them.”

“Damage caused to the inductor as a result of its proximity to the pan well roof”

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