anyone recommend an earth leakage clamp meter ?

[redwire]

The 60k reading will move - the multimeter (Ohms) DC current causes electrolysis like charging a battery with the water and metals there. Try flip polarity and watch the reading.
Another approach is measure DCV to get an idea if it's wet. 3-wire? Or measure Ohms between all conductors and the armour, 4 possible readings to see if how much is leaking to what.
Line/Hot will make water boil and steam and make gurgling sounds if immersed, as a give away.
If many wet readings, I'd prepare to dig up the splice. The water will eventually corrode the conductors and the cable go open circuit.

Do you have frost and soil heaves? That moves cables around unless 1-2m below surface here.

[petehall347]

also, is it roughly 60k or did you use a meter with lots of digits?
maybe a precision meter would help position it.

it settles roughly 60k .not exact as it does change a bit and takes a few seconds to settle like its also picking up capacitance which i expect on such a long run . i really should have use the megger on it , when i swap out the isolator switch i will use the megger instead of the dmm . i was nursing a huge hangover and shouldn't really have been messing around with live mains . i had to disconnect whilst checking stuff . where the wires connect to the supply is a dark place and my torch battery decided to run rather low on charge so was hard to see things . its a bit odd as a few times the 60k wasn't there at all and had me touching my meter leads together for my sanity . another thing i noticed was the armour was connecting to the earth wire so i guess there is a split letting water into the cable . i wa told there is a kink in the cable that's been there a long time but i haven't looked at that yet . might have to check that out to see if its getting warm .

[stj]

also, is it roughly 60k or did you use a meter with lots of digits?
maybe a precision meter would help position it.

[stj]

well, the constant resistance may be caused by carbon tracking!
i wonder if some type of RF injection would help find the spot?

[petehall347]

on another note it only has a 2 pole switch at supply end so going to swap that for a 40 amp mcb so the cable wont completely burn out if it hard shorts ..

[petehall347]

if you know where the splice is, try watering the ground and see if it trips!

thought about this but if the wet problem is underground surely it will stay wet for lots longer .. this problem goes away not long after the rain stops . its the 60k ohms between live and earth that is a clue here but find it odd its same reading no matter which end of the long cable i measure from unless its bad right near the middle . am hoping the issue is now fixed for now by disconnecting the earth wire . maybe not though thinking about it .

[stj]

if you know where the splice is, try watering the ground and see if it trips!

[petehall347]

today's findings with the swa cable .. disconnect both ends and checked resistance and getting 60k ohms between live and earth .this is same at both ends . disconnected the earth at supply end so now the earth wire is disconnected both ends .its ok because there is local earth rod as i made it terra terra anyway . funny thing is there is 9 volts showing between the disconnected earth and the ground rod . whether this is because of cable capacitance or leakage i do not know .. the trip hasn't tripped yet but its not raining .

[petehall347]

Where does this cable run?
Outdoor armoured cable (TECK cable) is plastic coated over the armour, then you have the plastic-jacketed conductors.
So you need at least the inner conductor's insulation being breached to have a ground fault or leakage.
Or there is a splice, and that's what is getting wet.

One site, we injected compressed air to see if it could make it to the other side.

we call it swa . plastic coat outside the steel wire armoured . there is one splice that was done years ago that's underground .i did that with a proper potted connector .
https://www.tlc-direct.co.uk/Main_In...SWA/index.html

[redwire]

Where does this cable run?
Outdoor armoured cable (TECK cable) is plastic coated over the armour, then you have the plastic-jacketed conductors.
So you need at least the inner conductor's insulation being breached to have a ground fault or leakage.
Or there is a splice, and that's what is getting wet.

One site, we injected compressed air to see if it could make it to the other side.

[petehall347]

you need a time domain reflectometer
BT used to have crude ones with crt's in a compact case, maybe you can find one on ebay.
or something more modern even.
https://www.youtube.com/watch?v=gw_JAc7l8CA

i have a seaward oscar 250 but think its no use for this problem . had it for years and not found a use for it yet . think its more fore for it shit .

[stj]

you need a time domain reflectometer
BT used to have crude ones with crt's in a compact case, maybe you can find one on ebay.
or something more modern even.
https://www.youtube.com/watch?v=gw_JAc7l8CA

[petehall347]

plot thickens 2 times tripping different days .. but getting close to the tripping issue ,, narrowed it down to one circuit when it rains . this is going to be fun . 10mm armoured cable approx 100 to 120 metres long . hoping its simply at one end or the other as pulling it up for visual inspection isnt going to be easy . if the ends appear good it will have to be cut somewhere near the middle to see which half is bad . or maybe use the megger and try and calculate where it might be . and of course i dont work in the rain so it might fix itself before i start . suppose i could connect a car battery to it and look for smoke coming out of the ground .

[petehall347]

loop tester turned up today . seems to work ok but i suspect it needs calibrating . when i get chance i will check it against the first one i bought .
back to the rcd tripping issue it's fixed now and no more nuisance tripping even during heavy rain .

[petehall347]

30mA is the common value for 240v

along with 100ma .

[stj]

30mA is the common value for 240v

[redwire]

North American GFCI mainly for shock protection and GFCI duplex outlets are 4-6mA here. I have one powering my workbench.
I see British duplex outlet 10mA but you're kinda dead?
Whole house RCD I guess is 30mA.

I did read cable capacitance can also cause false tripping, long runs >50m.

[stj]

you wont see a 10mA rcd on 240v - too easy to false-trip one.

[petehall347]

i cant remember ever seeing a 10ma rcd so cant see it being a problem .

[redwire]

It says the same thing - "25A test current (20Ω range) ... for 2 half cycles of AC (20msec)."
Have to do a teardown of one to see how they are pumping so much current through for the impedance test, yet it can take a mains surprise.
It looks really good. Don't use them in North America and we should.

The impedance test pulse might be fast enough to not trip a RCD, not sure what the response time of them is.
D-Lok for RCD's rated 10mA or less, might trip.