Welding a steel craft whilst afloat - electrolysis?

I cannot confirm nor deny that this situation is unusual. The fact is that you tie your boat in a marina an simply do not know what you connect to. There never is a sign "this socket has been installed by an *******".

A power company just delivers 3 phases and a zero, they have no influence on the equal distribution of loads and the conductivity of their ground electrodes.

After holiday guests in houses nearby complained that they sometimes could not take a shower because the water was stinging I investigated and found a differential of nearly 30 V. I installed a separate protective ground using a large surface ground electrode, isolated from the grid, which completely solved the problem in our area.

 

If you told the power company that their ground wire was 30V above earth I'd like to think that they would "influence" it before someone dies. But that doesn't help if you are there temporarily.

> do not know what you connect to
Yes, but you can measure it. Perhaps galvanic isolators should have alarms that indicate the blocking voltage has been exceeded - a good reason to either disconnect completely or use an isolation transformer.

 

It was even worse jonr.

I once told them they connected the phase to the ground lug of a new concrete post, but they said I was mistaken, they were professionals who do not make such stupid mistakes.
The concrete was too hot to touch and stayed that way during a whole winter, so they lost megawatts without noticing it. Only when I found a technician nearby and guided him to the post he sort of apologized, cut the power at the transformer station and cut the cable. It took another 2 weeks until a crew showed up and did the installation properly!

 

Sounds about like the quality of some oil well drillers.

 

I've never heard of electrocuted swimmers because of the conditions described in that post (small voltages on the grounding conductor). However, connecting the onboard ground to the onboard neutral (as is often done in distribution panels on shore) can cause significant currents to be sent into the water, sometimes enough to paralyze or kill- this does happen now and then, hence why it is generally prohibited to connect the ground and neutral wires on board. A similar situation can arise if there is an AC leak into a DC circuit (ie, a faulty battery charger) and the AC ground is not properly tied to the DC negative.

A gradient of six volts per metre is all it takes to kill a swimmer.

Hard to argue with that

If the boat is fitted with a proper isolation transformer and is wired to the appropriate marine codes (not shore codes), I don't see why any of the issues argued in the last page and a half of this thread would pose a problem. If it doesn't have an isolation transformer, or at least a galvanic isolator, you probably shouldn't be connecting it to shorepower in the first place, and the last page and a half of discussion becomes moot.

As for the welding question: I don't think a good DC welder, with its ground clamp affixed near the site of the welding, would leak enough current to cause corrosion problems.

Another quick observation on the grounding issue: There have been a lot of reports out of Toronto of dogs getting killed by stepping on manhole covers. Seems that a few of these things had become live and, when covered with water and salt (as is the case in winter), gave animals enough of a shock to kill them. People were safe, because nobody in Toronto goes barefoot in the winter.

 

> connecting the onboard ground to the onboard neutral

I second this. Check your boat and make sure that this was *not* done.

 

There is nothing stopping you from digging in your own earth plate or just used an isolation transformer. If the power supply earths don't do anything and there's no permanent earth wire then your earth leakage trips can never work and you will be dangerously affected by earth faults in others installations. You must live in a backward country!

 

An earth leakage trip or circuit breaker can only work on a down side earth fault and if you have a good enough earth return... so you cannot disconnect it!! Any voltage difference between the earth and neutral is usually due to faults elsewhere and current running through the earth system. If the supply earth is not good enough or non existant then you supply your own but it must be tested with an earth loop impedence tester. You can't do this using a boat as the earth because it is unreliable and moves around, each place, position and situation is different so that's why you need the tested shore earth which is relatively fixed.

 

That is a somewhat extreme example of ground not being at the potential you expect it to be. Quite surprising it happened in a civilized country.
That is exactly why I advise to distrust the ground connection of an AC outlet and isolate that from a boat's ground wiring.

That is of course correct Matt. Only the possible offset voltage on the ground wire could cause corrosion. It is connected internally to the metal case of the welder, so my advice is to put the welder on an isolating surface and treat it as hostile.
The welder output is floating except for a high resistance path to prevent static electricity. It must be, because you normally connect DC+ to the object and DC- to the electrode.

 

Lots of static on this thread today. Or are they echos?

Below is a schematic picture of a device invented by Gottfried Biegelmeier in 1957. It protects you against all of the dangers that could evolve from poor or damaged wiring, such as shock, electrocution, fire.
Note the complete absence of a ground wire!

The device is mass produced by companies like Moeller and Siemens. A sophisticated electronic version which trips at only 5 milli-amps costs approximately $ 85-100. It is a mandatory piece of equipment in the EU for all waterfront AC outlets.

The article is here: http://www.brieselang.net/fehlerstromschutzschalter.php

 

You are hard work! The first picture is schematic and shows only the test function! Further down in the article another circuit shows the full circuit with the earth or ground wire as the PEN wire (Protective Earthed Neutral conductor)! This however is usually combined in one wire but they are not allowed in special locations such as marinas.

Please look and understand that no earth leakage circuit breaker can work without an earth return! You might learn something if you listen to me instead of fighting me!

This is a good summary of the UK electrical regulations although now on the 17th edition with some changes to marina installations. You will find nearly all you need to know.

http://www.tlc-direct.co.uk/Book/1.1.htm

 

WRONG AGAIN!

If you could read German you would have understood that the ground wire in the second picture is not part of the ground fault circuit but of the over-voltage protection.
The GFI works without ground, it just measures and compares current.
For voltage you need ground as a reference, not for current. Any qualified electrician should know that.

I designed the electronic version almost 30 years ago....

 

Are you on some sort of drugs, they don't have over voltage protection or reference on the earth! Who are you trying to convince... yourself? Are you German?

This is an earth leakage circuit breaker with over current and over voltage protection, it needs an earth to operate the earth leakage protection. You are very confused as to the the operation and therefore I believe you lie about your involvement in this device.

Translation:

A further protection device for electricity mains is realized by the earth-leakage circuit breaker. It separates the supervised electric circuit from remaining electricity mains, if river on bad way flows. In addition the earth-leakage circuit breaker compares the hang-led with the returned amperage. In the electric circuit if a river is derived somewhere against earth, then is not in the sum current transformer the sum of and flowing back river any more zero. Develops a current difference, which leads to the release of the earth-leakage circuit breaker and thus to the disconnection of the current supply.

The Fehlersrtomschutzschalter was invented and patented 1957 of Gottfried Biegelmeier. Organization of the protection device for electricity mains: Over-current protection: (G) behind it hides itself the Leitungsschutzschalter (LSS), generally as protection designation. As soon as the consumers in the secured electric circuit more river would like to refer, than electricity mains are laid out, the over-current protection releases and separates the electric circuit. Overvoltage protection: (G) the operating voltage in electric circuit is supervised here. As soon as a transient overvoltage arises, as for example by a close thunderbolt, the overvoltage protection from us solves derives the overvoltage to the earth. The electric circuit is not switched off. Fault current protection: (And flowing backward rivers are alike to G) in normal operation. If the rivers should become unequal or it flow on protective grounding a river, the fault current protection closes on an error in the electric circuit and scolded off. With a combination of fault current protection and overvoltage protection at the equipment an overvoltage will draw always also a switching of the supervised electric circuit off. The derivative has a short circuited between L and protective grounding or between N and protective grounding to the consequence. Since and flowing backward rivers are no longer alike, scolded the fault current protection consistently off. Since the fault current protection does not contain over-current protection, additionally an over-current protection is always prescribed to the fault current protection. Devices, which contain both enclosures, are " as FI/LS switches or; Personenschutz" designated. Usually the execution is however separate, with priority in the annexe and/or the subdivision.

Structure of an earth-leakage circuit breaker The earth-leakage circuit breaker is based on a sum current transformer, which adds all to and from the consumer flowing rivers with correct sign. In the electric circuit if a river is derived somewhere against earth, then is not equal in the sum current transformer the sum of and to flowing back river zero. In the trip coil a tension is induced by the difference stream, which brings the relay with the latch to releasing.

With from the front the test key accessible at the earth-leakage circuit breaker the case of an error can be simulated, in order to examine the normal function regularly. By pressures of the key an outgoing phase is connected over one suitably dimensioned resistance with the neutral leader before the earth-leakage circuit breaker and in such a way wanted a fault current produced, which exceeds the trigger current strength. Manufacturers recommend a half-yearly examination. Localvariable earth-leakage circuit breakers must be examined daily before beginning of work for function.

Dimensioning Earth-leakage circuit breakers are differentiated on the basis of 3 substantial parameters: Switching capacity (indicated in kilo Amperes [kA]) Working current (indicated in ampere [of A]) Fault current (indicated in milliampere [mA]) Switching capacity Switching capacity or also resistance to short-circuits indicates the max. amperage, with which a switched off or released earth-leakage circuit breaker the electric circuit can still interrupt. Starting from a certain amperage an arc between the opened contacts can develop and develop so an appropriate heat development. Good earth-leakage circuit breakers for private households have a switching capacity of 10kA.

Working current The working current is the amperage some earth-leakage circuit breaker permanently to lead can. In private households 16A earth-leakage circuit breakers are usually used. Fault current (G) The fault current strength indicates, but some earth-leakage circuit breaker releases. In order to ensure a protection of individuals, an earth-leakage circuit breaker must release latest starting from a fault current - thus the difference between outgoing and again detailed river - of 30 mA and interrupt the electric circuit. For fire protection only a fault current of 300 mA is prescribed. It pay attention that an earth-leakage circuit breaker does not limit the height of the fault current. The protective effect is exclusively based on the fast disconnection of the current supply.

Regulations The use of earth-leakage circuit breakers becomes additional in many countries in the household and industrial range at least for plug sockets to 20The installed over-current protection. In Germany fault current protection for humid rooms and plants in the external area are already prescribed since 1984. Since that the legislator except for few exceptions demands 01.06.2007 additionally also for all other plug sockets to 20A, which are intended for the general use, a fault current protection with a fault current of maximally 30mA. This regulation affects itself extremely with electric circuits, which are equipped with an overvoltage protection additionally. Plants, those in enterprise to be permanent must - like cooling systems, safety systems and telecommunications - by occurrence of small overvoltages would on a long-term basis be switched off.

Practice In many cases it is compatible, if an overvoltage protection releases the fault current protection. As soon as always a person locally is, as long as the system is used, this person can the condition of the system examine and if necessary manually restart. For all other cases there are only two solutions: Electric circuits divide in electric circuits with overvoltage protection and electric circuits with fault current protection Installation of a Wiedereinschaltautomatik Electric circuits divide if one considered that overvoltage protection is with priority an equipment protection and a fault current protection priority a protection of individuals, can one in many cases a meaningful allocation find. Stationarily claimant devices, which are permanently operated, are affected only in rare cases directly of persons. Freely accessible plug sockets in those mobile devices to be operated should be provided against it with fault current protection

Möller restarting automat Restarting automat (G) in the subdivision beside the earth-leakage circuit breakers are placed. With a small flag the rocker switch of the automat is restarted. Different modes of operation specify the number and distances to further switching on attempts. Usually 1 to 5 attempts are offered. Permanent restarting is not offered, because in the actual case of an error - thus no transient overvoltage - which would then be loaded system only additionally.

Security is always given: If a FI-protective switch switches the electric circuit off by a derivative of an overvoltage protection, protective grounding is not separated of it and the derivative of the overvoltage is further given without restriction. If electric circuits should have been separated from the central fault current, in order to be able to ensure their permanent enterprise, partly also freely accessible plug sockets for mobile devices are present. These can become simply by the Kopp protection of individuals as protection of individuals secured. It is laid out as inserts and can preferably before connector strips merged.