Acceptable leakage on shore power ground wire

[MikadoII]

I have measured the AC and DC current on the green earth wire in my shore power cable.


DC - 0.5 microamps


AC - 230 microamps everything plugged in
130 uA with nothing but the isolation transformer connected
45 uA with the main breaker off


Are these figures considered acceptable please?

[Orin]

Interesting. Truth be told I have no idea. Given a while I could probably calculate something or get ahold of one of my boat corrosion and preservation experts… but what I would ask…
Any leakage means some amount of corrosion. That said some amount of corrosion is going to occur no matter what…. And those current values are below many peoples instruments ability to accurately measure given natural phenomena become measureable at those scales.
Do you have any current problems or is this academic?
Do you currently have a galvanic isolator onboard? It’s my preferred method for addressing issues like this if you’re experiencing faster than normal corrosion.

[smac999]

Are you using a $10,000 piece of lab equipment?

A gfi trips at 5ma. An elci trips at 30ma. 0.045ma Is nothing…. And if using a regular meter I’d call that 0 anyways.

[MikadoII]

My normal Fluke cannot get anywhere near uA. I used an el cheapo Jaycar Digitech meter that claims a range of 200uA AC or DC. The readings appeared to be quite repeatable.



Some time ago I did have a corrosion problem of the prop. It appears that the installation of an isolating transformer has at least alleviated that.


My feeling is that the DC reading is probably of no concern and that the AC reading could be capacitative coupling.

[CharlieJ]

OP:
You do not have an electrical leakage problem as your isolation transformer eliminates the return path to the shore power source via the safety ground. Note that you could develop an indicated leakage issue if you had a partial N>G in the shore cord/shore power inlet system.

BTW, on boats without isolation xfmrs, I rarely find <5mAAC leakage (and have found as much as 13A!!!) when clamping the L and N (120VAC service) or L1, L2 and N (240VAC service).

[Jammer]

Originally Posted by MikadoII

Are these figures considered acceptable please?

They are acceptable, very good in fact. AC, anything under 5 mA is OK. Anything under 0.5 mA is fantastic.


On the DC side, one mol is 9.648×104 Coulombs.


You state that you have 0.5 microamperes, or 0.5×10-6 Amperes, of DC leakage. An Ampere is one Coulomb per second. This gives you, with some basic arithmetic, 16 Coulombs of galvanic corrosion per year or 1.6e-4 mols. I'm a little fuzzy on the electrochemistry of galvanic corrosion but a zinc anode has an atomic number of 30 and a typical ionization state of +2, so each mol of electrons will ionize 15 grams of zinc. Total of 2 mg of zinc. Basically nothing.


My math is probably wrong...

[Bowdrie]

Originally Posted by Jammer

An Ampere is one Coulomb per second.

I thought that one Coulomb per second = 1 Watt/Second.
One Amp at one Volt.
Anyway, the figures for Zinc erosion are quite interesting, but I know electrons don't weigh very much.

[MikadoII]

Thanks everyone for your thoughts and comments.

[AKA-None]

Just to note
Repeatable does not equal accurate

[MikadoII]

Originally Posted by AKA-None

Just to note
Repeatable does not equal accurate

Of cause not. At least, the dvm is not reacting to a passing seagull.

[tanglewood]

Originally Posted by smac999

Are you using a $10,000 piece of lab equipment?

A gfi trips at 5ma. An elci trips at 30ma. 0.045ma Is nothing…. And if using a regular meter I’d call that 0 anyways.

I think the tongue-in-cheek in this comment was missed.


Are the numbers you are reporting micro-amps, or milli-amps? There is a thousand times difference. I *think* you mean milli-amps which is what most decent meters will read.


Are you really reporting uA, or is it mA?

[MikadoII]

Originally Posted by tanglewood

I think the tongue-in-cheek in this comment was missed.


Are the numbers you are reporting micro-amps, or milli-amps? There is a thousand times difference. I *think* you mean milli-amps which is what most decent meters will read.


Are you really reporting uA, or is it mA?

uA. The meter is an el cheapo but claims a 200 uA range. (My normal Fluke will not go anywhere near uA)


The general consensus is that I do not have a problem.


Thanks.

[lestersails]

Originally Posted by AKA-None

Just to note
Repeatable does not equal accurate

Agree!