Testing problems need a little help.

[kes123]

Hi all. i am new to all this and just practising on my own system using megger 1552.
Trying to do measurement of the external earth fault loop impedance (ze)

So i have isolated, removed main earthing conductor.
I have then connected one probe to the earth that I have disonnected and the other lead to the incoming line on the supply side.

This is a live test and i have set my megger to no trip. the unit then beeps but only picks up a voltage of 157volts and then goes to error.

is it me, well i know it is but what am i not doing right

cheers

 

[trypod]

No trip is a 3 wire test on the 1552

 

[telectrix]

you don't use no trip for Ze. only use no trip when measuring Zs downstream of an RCD. the no trip test is a 3 lead test. thats why you're getting errors.
think you are connecting correctly. 2 leads. red to L, black to E. set megger to Hi.

 

[malcolmsanford]

Telectrix is our megger man and he will be along I'm sure for this.

On my meter which is a martindale veritest you check the Ze on the hi test not the soft non trip test, though I doubt that would give you an error code, all it will do is give you perhaps a higher than expected ohmeric reading.

 

[telectrix]

must have posted while you were getting your fingers into gear, malc. LOL.

 

[malcolmsanford]

must have posted while you were getting your fingers into gear, malc. LOL.

I know your a meggar man mate so left it to you, but I thought like the martindale you have to do it on the hi test 2 lead and like the Veritest the soft test is 3 lead .....................

 

[telectrix]

yep, hi current 2 lead for Ze on megger. think the new megger will do a soft test 2 lead now.

 

[kes123]

Hi just to clarify. I set megger to hi, connect one end to disonnected earth and the other to the line.

When I do this it shows 230volts then trips the system

 

[malcolmsanford]

Why would you want to do a soft test Ze ??? is something happening that being here I've missed

 

[telectrix]

you should be connecting to the "live " side of your main switch, with the switch OFF

 

[telectrix]

Why would you want to do a soft test Ze ??? is something happening that being here I've missed

op is learning how to use the tester. suggest buying christopher kitchers book. "guide to inspection and testing". also, read the instructions for the megger.

 

[topquark]

Guessing you have an RCD as your main switch. As Tel says ^^^^ main switch should be off and use the supply side not load side.

 

[malcolmsanford]

Hi just to clarify. I set megger to hi, connect one end to disonnected earth and the other to the line.

When I do this it shows 230volts then trips the system

Again wait for Telectrix but are you testing on the load side of an RCD when your doing this?

If you have disconnected the main earth conductor the installation should be Off mate, and so nothing should be tripping, please please be careful, by the sound of things you have disconnected the earth, and left the installation off.

Do you have an upfront/seperate from the CU RCD by any chance either?

 

[malcolmsanford]

yep, hi current 2 lead for Ze on megger. think the new megger will do a soft test 2 lead now.

Sorry Tel I think we crossed each other there, when you said a 2 lead soft test I was thinking why would you want to do a soft test on a Ze, hence my question. Is this 2 lead soft test designed for non socket circuits that have RCd protection, say a light circuit

 

[telectrix]

yep. the megger 1700 models are capable of doing a 2 lead soft test, whereas all earlier models was a 3 lead test ( so i am lead to believe, anyway )

 

[kes123]

Hi, I am being careful. ok so one probe to earth and one probe to line with the system switched off.

megger set to loop Hi. No reading is given.

 

[malcolmsanford]

Which side of the RCD are you puting the probe son on the supply or load

 

[topquark]

yep. the megger 1700 models are capable of doing a 2 lead soft test, whereas all earlier models was a 3 lead test ( so i am lead to believe, anyway )

Mine (1553) requires 3 leads for a soft test and I had heard that the new ones have a two lead soft test.

 

[topquark]

Hi, I am being careful. ok so one probe to earth and one probe to line with the system switched off.

megger set to loop Hi. No reading is given.

Check which ports on the megger your probes test leads connected to.

 

[Amp David]

Hi, I am being careful. ok so one probe to earth and one probe to line with the system switched off.

megger set to loop Hi. No reading is given.

You mustn't being doing as the others have said.

Put the red probe on the incoming side of the main switch and the gree to the disconnected earth.

Are you testing at the origin or a an RCD protected submain?