[PSUBS-MAILIST] DNVGL

[via Personal_Submersibles]

Sean,

The positive has 4 fuses in the box (4 legs) in the case one leg fails you still have power and in the case of a dead short prior to the breakers that the fuse will blow. Once the cable penetrates the hull it goes to a double pole breaker then distributed from there. The negative is a single cable with one fuse and once it penetrates the hull it goes to a double pole breaker and distributed from there.

I completely agree the shielding of the battery cables is a good idea because of strength of the cable and to help if the insolation is cut by something. The part where I struggle with is why ground the shield of the battery cables to the hull? The only thing that could make sense is fault indication on the battery main cable. Is that the reason?

Thank you,
Scott Waters

>  -------Original Message-------
>  From: Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org>
>  To: personal_submersibles at psubs.org
>  Subject: Re: [PSUBS-MAILIST] DNVGL
>  Sent: Oct 21 '17 16:01
>  
>  I presume that even in the unlikely event of the double isolation
>  failure which could create a short circuit current, that the DC mains
>  are also protected as close as is feasible to the batteries by some
>  manner of fuse or circuit breaker?
>  
>  Sean
>  
>  Sent from ProtonMail mobile
>  
>  -------- Original Message --------
>  On Oct 21, 2017, 14:02, River Dolfi via Personal_Submersibles <
>  personal_submersibles at psubs.org> wrote:
>  
>  Sean,
>  An alarmed device to measure leakage to ground on all polarities is a
>  requirement for DNVGL, recently made a requirement for ABS, and was
>  original equipment on Pisces VI. Fortunately, it is an easy thing to
>  implement.
>  
>  I understand that because negative and ground are separate that
>  without a second fault on the negative side there will be no current
>  flow, but why tempt fate? Maybe I'm thinking into this too much.
>  
>  -River J. Dolfi
>  
>  -------------------------
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