earth leakage clamp meter

[shadyspark]

recently got given a megger earth leakage clamp meter, i realise it will be handy for houses with nuisance rcds caused by appliances to a certain extent however can i use it to determine earth leakage on the circuit with no load connected?

ready somewhere this could be a quick alternative to an IR test as there would be no need to disconnect appliances but im not convinced

 

[securespark]

How does your theory go?

 

[shadyspark]

how does my theory go? probably out the window once i start using it

 

[holmslaw]

..

 

[shadyspark]

right then say the house is drawing 10amps and leaking 5ma, would this mean if the house used 60 amps the rcd would trip at 30? or would it depend on aqppliance leakage?

 

[ricicle]

It depends on :-

What is leaking - wiring or appliances ? (energised wiring will leak all the time if the fault is constant, appliance only when they are used)

How much leakage (damp can cause more leakage for example)

How is it leaking L/E or N/E (what is the imbalance in the toroid) ?

The ratios will hardly ever be linear

 

[shadyspark]

in my job, im more focused on the wiring faults, if say the the L-E ir test showed up 10Mohms would this circuit leak to earth if energised but no load drawing through it?

its just domestic faults that im called out to, so only transformers would be on the bathroom lights, shaver point etc

 

[ColJack]

oh boy...

no load = no current flowing..
you can't get a leak out of a hosepipe if there's no water in it.. same thing with a live wire..
no current = no leak..

 

[ricicle]

Yes a shaver transformer would draw a small amount of magnetising current even off load.
If you use Ohm's law you could work out an approximate leakage if you know the IR.

 

[ban-all-sheds]

Won't leaky insulation have some dielectric properties?

 

[ricicle]

oh boy...

no load = no current flowing..
you can't get a leak out of a hosepipe if there's no water in it.. same thing with a live wire..
no current = no leak..

But there will be a leakage current flowing inversely proportional to the IR of the fixed wiring, regardless of whether or not a load is connected.....

 

[ColJack]

then with no load, leakage current = total current, so a regular clamp meter on the live wire will tell you what's leaking to earth..

 

[shadyspark]

lol, what is it with people comparing electricity problems to everday life?

surely a fault will lessen resistance and increase current?

if the resistance l-e is 10,000ohms, 240 volts? 240/10,000 = 0.024

so if i ir test a l-e fault to be 10Mohms will it leak 24ma?

or am i talking pish?

 

[ricicle]

then with no load, leakage current = total current, so a regular clamp meter on the live wire will tell you what's leaking to earth..

Only if you disconnect everything particularly any transformers.....

A better way is to have the clampmeter around both L+N tails. Any difference between the two will show up on the meter - this will be leakage current.

 

[Spark123]

lol, what is it with people comparing electricity problems to everday life?

surely a fault will lessen resistance and increase current?

if the resistance l-e is 10,000ohms, 240 volts? 240/10,000 = 0.024

so if i ir test a l-e fault to be 10Mohms will it leak 24ma?

or am i talking pish?

You are a factor of 1000 out, 10,000Ω= 10KΩ,
10,000,000Ω = 10MΩ