Also - the DC electrical should be a non ground-referenced system (neither terminal connected to chassis / safety earth), so a single failure which shorted either side of the DC mains to ground would tie these potentials together, but should not result in any sustained current flow. An alarm which alerts you to the presence of continuity between the hull / safety earth and either battery terminal should be present to warn you of such a short and allow you to fix it before a second fault to the other side of the battery actually creates a short circuit at battery potential.<br><br>Sean<br><br><br>Sent from ProtonMail mobile<br><br><br><br>-------- Original Message --------<br>On Oct 21, 2017, 11:11, River Dolfi via Personal_Submersibles < personal_submersibles@psubs.org> wrote:<blockquote class="protonmail_quote"><br><html><head></head><body><div dir="ltr"><div>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. <br></div><div> <br></div><div>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.<br></div><div><div><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div>Thanks,</div><div><br></div><div dir="ltr">-River J. Dolfi</div></div></div></div></div>
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