Thanks for the enlightenment, particularly Rapaire's history lesson and Shanhaiceltic's technical talk. I'm just talking out loud here, and due to my ignorance I'm not understanding all of what happened, though it seems clear if they had a nasty fire they sure could have lost the ship and are probably fortunate that, tragic as it was, they suffered no more than one fatality.

I'm wondering what 'era' these subs are from. They can't be too old, or they wouldn't be worth having. Military technology lags behind civilian in that it has to be proofed for wartime use, hence several times as rugged as what one would see in civilian life.

From the above referenced article:

During that repair work a rogue wave washed over the submarine, sending 2,000 litres of sea water cascading through the open hatchways into the control room, where it soaked high-voltage wires, causing the fire.

The fire knocked out power in the boat, leaving it adrift in heavy seas.


Most subs are powered by battery banks, as an example the American WWII sub I was mentioning above had two banks of 126 cells each, putting the service DC voltage at roughly 400 V. In order to power 1000 horsepower motors, you end up with currents in the 2000 Amp range, which is huge, and calls for big honkin' cables. The voltage, however, is not 'high' by electrical terms, and (in civilian life) doesn't require thick insulation. The technical side probably comes around the terminations, sealing them off, and in the case mentioned in the report, of control panels. Where electricity is concerned you've got to be sealed off 100% and that is hard to do against seawater and pressure. Over time all insulation degrades due to mechanical strains, plastic decomposition (very slow, though), and, depending on the voltage, electrical stress.

Since the 70's there might have been changes in design for utility and efficiency involving putting the DC through an invertor and generating AC onboard, in which case there could be all sorts of voltages, which electrically call for more elaborate insulating measures. This would be anything over 600 V. In theory it can still be insulated, but above 4000 V it gets to be much thicker, more expensive, and lifetime limited. The big saving, however, is that you can transmit power over much smaller cables, and with AC you have a lot more sophisticated control possibilities.

There should always be a sophisticated electrical circuitry protection system which 'trips' shorted cables. In each system there may be cables which are sacrosanct, such as fire protection power systems, which are not worth having if they can trip off, but in those cases those systems are heavily overbuilt.

The news article linked above, if I read it correctly, mentioned 2000 litres of seawater coming down the hatches, which amounts to about 500 US gallons, which is a few 'bathtubs' worth of water. It should go through drains in the floor to some sort of sump. In other words, 2000 litres doesn't sound like much.

Thank you for tolerating my words, written from lack of knowledge. I enjoy reading the more experienced posts to this thread.