Liquid Nitrogen to the rescue: How to fix a 230kV oil filled electricity cable.

1 minute read.


This is still one of my favourite mad engineering stories on the web. How to fix a 230kV oil filled electricity cable with Liquid Nitrogen.

It turns out they have a problem with an underground wire. Not just any wire but a 230 KV, many-hundred-amp, 10 mile long coax cable. It shorted out. (Lotta watts!) It feeds (fed) power from the Scattergood Steam Plant in El Segundo to a distribution center near Bundy and S.M. Blvd.

To complicate matters the cable consists of a copper center conductor living inside a 16 inch diameter pipe filled with a pressurized oil dielectric. Hundreds of thousands of gallons live in the entire length of pipe. Finding the fault was hard enough. But having found it they still have a serious problem. They can’t afford to drain the whole pipeline – the old oil (contaminated by temporary storage) would have to be disposed of and replaced with new (pure) stuff which they claim takes months to order (in that volume). The cost of oil replacement would be gigantic given that it is special stuff. They also claimed the down time is costing the costing LA $13,000 per hour. How to fix it and fast?

That’s where the LN-2 comes in. An elegant solution if you ask me. They dig holes on both sides (20-30 feet each way) of the fault, wrap the pipe with giant (asbestos-looking) blankets filled with all kind of tubes and wires, feed LN-2 through the tubes, and *freeze* the oil. Viola! Programmable plugs! The faulty section is drained, sliced, the bad stuff removed, replaced, welded back together, topped off, and the plugs are thawed. I was amazed.

Source: engineering pornography

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