Mains transients, or Electrical supply transients, on yachts?

[Faringdon]

Hi,
What are any features of mains transients on Yachts/Super-Yachts? (from 16 foot to 100 foot).
Is it a worse situation than the National Grid, or more benign?
How much of a problem is lightening in this respect.
How bad are common mode transients compared to diff mode transients.

Speaking of systems supplied from DC battery, and those from say diesel generator.

Whats the worst mains transient you tend to get on Yachts?

I guess you can't get the "Loss of neutral" problem, as they are all going to be single phase?
Are any 400Hz used on Yachts?

Do they tend to be DC , or AC distribution?
Do you get Load Dump issues?

Do you have to be a qual'd Electrician to wire up a yacht?...or does it tend to get done by the owner hacking about? What problems can such hackign cause.

Sorry i did google this but the info is not concise and is unclear to what they are referring
eg
https://forums.sailboatowners.com/threads/voltage-spikes-in-marine-electrical-systems.177228/

[dmills]

Done some stuff on a 30M class vessel, it tends to a mix of (In our case) 24V DC and 230Vish AC, sometimes you see three phase delta used to avoid the neutral and the risks of electrolytic corrosion that sometimes brings, mainly a party trick on larger ships.

When running on generators, frequency can be a little variable and brown outs are a bit of a thing when someone throws heavy loads on, the DC supplies will (if engine driven) suffer from all the usual automotive shenanigans, especially if there are annoying things like DC powered bow thrusters that can pull maybe 150A down a pair of DC cables the length of the damn boat, the transient from the contactor on that can HURT.
Sometimes, particularly when mains is derived from an inverter you need to check fault clearance carefully, often the supply is not stiff enough to take a fuse or breaker in reasonable time.

Navigation will NOT appreciate DC wiring with any loop area near the compasses.

The other thing to watch about the DC side is that electrolytic corrosion is very much a thing, and the voltage drop on a negative return can put the case of incautiously designed gear far enough away from the hull to cause rot to happen surprisingly fast, cap couple the chassis to negative wire, don't bond them. This can get 'interesting' with the radios....

On the mains side, shore power in marinas is in truth a complete shit show, a smart boat owner has a honking great isolating transformer with the secondary treated as a separately derived supply and the shore power earth bought nowhere near the on board doings, the issue is TN-C-S and the voltage drop in the neutral being imposed between your hull and the marina structure via the earth conductor, it can be quite sufficient to eat your anodes.   

Oh, yea, salt spray gets into EVERYTHING, just assume it will get in and pot everything not in an ATEX enclosure (and even then...).

[SeanB]

Yes, take the 12V/24V side, and treat it like you are in a 1980's Jaguar XJ, with the horrid Lucas electrical putting 200V spikes on with every ignition pulse off the coil, and the dynamo merrily taking the battery voltage from 10V to 30V as it cycles on and off, plus all the rest of the fun of wet electrics like Lucas can deliver. Never seen a boat with good electrics, unless it was brand new, and had never actually been in the water yet, all were a mix of corroded wires, corroded connections and nasty. Connectors you want to use those that Yamaha uses, those, with judicious application of the right silicone grease, will survive well, though the crimping tools are expensive, along with the right waterproof double sleeved wire, because your normal wire from the local hardware is going to be permeable to some extent. Marine grade cables exist for a reason, along with the connectors.

With the 230VAC (or 115VAC, often using the same type of plug and socket, and no marking as to voltage) you also have all sorts of sags, surges and spikes as well, plus you will either need good filtering, make sure most of the stuff is class 2, and does not need a protective ground, and is double insulated, plus has some decent surge suppression in it. Oh yes, also should work off square waves with massive harmonics on it, because that is what most inverters will give, none of this sine wave well regulated supply here.

[jonpaul]

Alternator or generator load dump transients 70 V many joules use MR2525 transients clamp diodes

j

[fcb]

10-18ft treat like a caravan. Very unlikely to have anything on it at all.

Inboard (fishing dayboats typically 18-27ft) treat like a truck, can be 24V.  Alternator typically on an inline diesel engine for charging battery.  May have seperate batteries for starting and aux.
Outboard (fishing/dayboats), probably have alternator built into outboard motor.

Perhaps 30-50ft will likely have seperate generator for significant hotel load when at anchor, especially if pleasure craft.

Beyond 50ft will typically have generator(s) for hotel load (AC/fridges/lighting/etc..).

The only rule-of-thumb is there is no rule-of-thumb. These systems can get very complex in the bigger boats (50ft+).

I haven't seen to much in the form of spikes, etc.. and even the synthesized mains (Victron etc..) is OK. But assume there is terriable stuff out there.
Earthing can be problematic on all craft, most of the smaller stuff (typically <70ft) is GRP.

Go and watch some Aquaholic YT videos, he does alot of reviews and nearly always shows the AC/DC panels, engine rooms, etc..