Leaking Shore Power Cable

[makesure]

Hi,
So, I have a 25' shore power cable (Marinco on one end and SmartPlug on the other) that pops the breaker instantly when plugged into the dock and not into the boat.
It worked fine at my previous marina but my new slip recently upgraded to the new AFCI standards.
Right now, my spare cable works fine so I am using that.
These cables are expensive so I'd like to fix it. I've replaced both ends so I'm pretty much convinced that there is a leakage in the wire itself. There is no sign of any physical damage to the cable.
Other than randomly cutting the cable into smaller pieces, is there any way to detect where the leakage is on the wire?

Thanks!

 

[alldodge]

So, I have a 25' shore power cable (Marinco on one end and SmartPlug on the other) that pops the breaker instantly when plugged into the dock and not into the boat.

If plugged into the dock and when plugged into the boat there is no issue.
If plugged into the boat and when plugged into the dock it pops the breaker

Or did I miss something?

Also what size cable?

 

[makesure]

If plugged into the dock and when plugged into the boat there is no issue.
If plugged into the boat and when plugged into the dock it pops the breaker

Or did I miss something?

Also what size cable?

It pops even when not plugged into the boat and only plugged into the dock.
It's a 30amp 25' cable

 

[alldodge]

Thanks
Old cable works, new cable does not

I would start with ringing out the wires. Use an ohm meter and ring individual wires, and also verify max resistance between each wire with the other 2

 

[dingbat]

duplicate

 

[dingbat]

The AFCI are monitoring the potential (differential) between positive and negative. Any variance is assumed a “leak” and trips.

Check resistance on each leg and for continuity (leakage) between positive, negative and ground.

Makes sure negative and ground are not reversed.

 

[makesure]

Thanks for the responses, they are all generally helpful. However, I've checked the resistance, ohms, etc. Everything looks good.

My question, specifically, is if I have a ground fault somewhere in the cable due to a break or broken down insulation, that does not show up on the meter, can I isolate exactly where on the wire the fault is occurring?

 

[mike_i]

Did you set the ohm meter on the highest resistance scale then measure between each wire? You should read an open or OL depending on your meter.

 

[dingbat]

Thanks for the responses, they are all generally helpful. However, I've checked the resistance, ohms, etc. Everything looks good.

My question, specifically, is if I have a ground fault somewhere in the cable due to a break or broken down insulation, that does not show up on the meter, can I isolate exactly where on the wire the fault is occurring?

What is “good”?
Are the numbers identical?

To check insulation you need a known load.
Check voltage at source and compare to voltage at end of cable. Then check each leg referenced to ground.

If it’s a homemade cable I would start by removing, inspecting and rewiring each connector.
The only way to isolate the problem in a cable is to start cutting.....

 

[alldodge]

Agree or
test insulation resistance use a Megger which applies the load and test, but not many have those

 

[poconojoe]

Agree or
test insulation resistance use a Megger which applies the load and test, but not many have those

Great suggestion, but as you said, most people don't have a megometer.
Instead of guessing or hacking it up, maybe it's time for a professional inspection of the cable.
Can the cable be taken to or sent out to be thoroughly tested? I'm sure there are places that can do this. It might be worth it since the cable is so expensive.

 

[alldodge]

I don't know of one, but I'm sure there are some

In most cases its the connectors that cost, 10 gauge 3 strand shore power cord is about $3 a foot. Might find it cheaper but would have to do some looking. My guess is it will cost more to test then buying a new cable

Just found 10/3 STOW cable for 1.66 ft
https://www.wireandcableyourway.com/10-3-sto-flexible-portable-cord-white-600v-ul-csa

 

[froggy1150]

Are the recepticals afgi or gfi? 2 different animals. Gfi looks for current loss to ground. Arc flash looks for actual arcing. Plugging in a cord with any load on it will create an arc and trip. Also running a motor with brushes can set thise off too. This is a factory made cord so without cutting a megger might check it. They put 1000/10000 volts out and if there is open insulation the arc will jump across and the meter will read some resistance. Thats how you check for bad winding in a motor. An ohm meter wont do that.

 

[ConchPirate]

When you say resistance is OK, are you measuring each of the wires end to end? You need to check between the wires. Measure resistance between the hot and neutral, then hot to ground, the neutral to ground. All 3 measurements should be infintly open and showing no resistance, if you get a reading between any two then the leakage is between those two wires. Figuring out where may be impossible with a standard VOM. But you could try stretching it out and connect the VOM on diode setting. If no sound detected when connected between the two suspect wires then start manually flexing the cable along its length and if the VOM emits a tone that may ge where the leak is.