[PSUBS-MAILIST] DNVGL

Sat Oct 21 15:12:55 EDT 2017

Noise rejection is not the only use case for cable shielding. Specifically in consideration of shielding which is also a physically robust wire braid, it is, in fact, indicated around power cables specifically because a tool or other object which inadvertently cuts into the cable will likely short that power into the shield, versus into the tool or cutting object which likely has some resistance, and it also provides a physical barrier such that inadvertent contact which cuts into the cable at all will be arrested physically as it is electrically in contact with only the safety earth potential. Think of putting a utility knife to it. You don't want to be able to slice through neoprene, PVC or polyolefin like a knife through butter and contact the core without something getting in the way for safety.

Sean

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-------- Original Message --------
On Oct 21, 2017, 12:55, Scott Waters via Personal_Submersibles wrote:

> Sean,
>
> On a DSV the batteries are in a separate compartment filled with oil. The cables go from the battery box to the hull.
> My interpretation of the rule is it did not consider this.
>
> Thank you,
> Scott Waters
>
> Sent from my U.S. Cellular® Smartphone
>
> -------- Original message --------
> From: "Sean T. Stevenson via Personal_Submersibles" <personal_submersibles at psubs.org>
> Date: 10/21/17 1:41 PM (GMT-06:00)
> To: personal_submersibles at psubs.org
> Subject: Re: [PSUBS-MAILIST] DNVGL
>
> Scott and I have been driving ourselves crazy trying to interpret the DNVGL rules on subsea electrical cables. We think that the essence of the problem is that DNVGL lacks rules specific to oil-compensated external battery banks (except being subject to "approval by the society"), and to the best of our knowledge DNVGL has yet to certify any submersible with external ambient batteries.
>
> One rule in particular is making us scratch our heads. UWT pt4 ch8 sec2-1.3 states that "All cables in the outer area shall comply with (cargo ship cable rules section). All cables shall have an EARTHED braiding or screen around the conductors and be equipped with an insulating outer sheet." If this is applicable to the main battery cable, damage could potentially create an incredibly dangerous ground fault condition where high voltage is passed to the sphere. While this requirement makes sense for low-voltage electronics who require protection from electromagnetic interference, it appears to be nonsense when applied to a high-voltage DC power cable.
>
> Thanks,
>
> -River J. Dolfi
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