excessive noise

[beanzntoast]

Its me
Hi all,i have a question maybe a simple one for the majority of you.It's a domestic TT system,When testing Zs of a lighting circuit with the megger 1553,the symbol for excessive noise on the circuit keeps popping up (the wavey line, those who use the meeger will know which i mean).My question is from your experience what are the possible causes when it shows that there is excessive noise on a circuit,thanks in advance
Jason

 

[beanzntoast]

Anybody have any ideas or doesn't this make any sense what i have posted

 

[Notsosmart]

Ok I'll have a dip; you have excessive noise in the circuit

Sorry couldn't resist it, unfortunatly I don't own that type of meter so I'm no help whatsoever & shall dive back into my foxhole.

But before I go are there a number of fluorescants in the circuit?; as they create all sorts of harmonics & so create a lot of noise (or voltage spikes)

P.S. By your picture arn't you a little young to be undertaking testing ;0)

 

[Deleted member 9648]

Never heard of an excessive noise function on a meter but would point out that the advise now from the NIC is not to Zs lighting circuits... add the R1-R2 to the Ze to obtain the Zs. I'ts deemed hazardous to access live terminals in lumminaires I think....so sod the excessive noise and don't bother.
By the way I'm guessing the excessive noise your meter is picking up would be due to an inductive load..(chokes?) or perhaps L/V electronic transformers which can generate interference I believe.

 

[beanzntoast]

Ok I'll have a dip; you have excessive noise in the circuit

Sorry couldn't resist it, unfortunatly I don't own that type of meter so I'm no help whatsoever & shall dive back into my foxhole.

But before I go are there a number of fluorescants in the circuit?; as they create all sorts of harmonics & so create a lot of noise (or voltage spikes)

P.S. By your picture arn't you a little young to be undertaking testing ;0)

I'm a big boy now i've just gone 1 last month ,ha ha it's my son all i can say he's as cute as his dad.Anyway back to the OP thanks for the reply also wirepuller but thats what i couldn't understand no flourescents on the circuit & also no LV transformers.I know thats the way to go adding Ze to R1+R2 to get Zs but how often is that answer even close to the Zs reading when you do a Zs test,It's usually way out.Thanks for all your replies anyway
regards jason

 

[NoSparks]

I have a different meter but could it be a disconnected earth. If the earth is broken you get induced voltage on the earth through induction which in the worst case can be quite high and give a nasty shock.

 

[c.boy]

Its me
Hi all,i have a question maybe a simple one for the majority of you.It's a domestic TT system,When testing Zs of a lighting circuit with the megger 1553,the symbol for excessive noise on the circuit keeps popping up (the wavey line, those who use the meeger will know which i mean).My question is from your experience what are the possible causes when it shows that there is excessive noise on a circuit,thanks in advance
Jason

hi yeah ive had that quite a few times!!! can mean that the main earth is breaking down and inducing a voltage but highly unlikely!!!! twin and earths next to conduit ,flats and always on the lighting circuit!!!these are the times it appears on my tester!!! switch it off and try again its the only way i have asked numerous electricians and no 1 has the answer be intrested in hearing more tho!!

 

[castlon11]

I'm a big boy now i've just gone 1 last month ,ha ha it's my son all i can say he's as cute as his dad.Anyway back to the OP thanks for the reply also wirepuller but thats what i couldn't understand no flourescents on the circuit & also no LV transformers.I know thats the way to go adding Ze to R1+R2 to get Zs but how often is that answer even close to the Zs reading when you do a Zs test,It's usually way out.Thanks for all your replies anyway
regards jason

It's irrelevant if the readings are far out as your dead tests are the definitive readings of the installation and are not subject to voltage change as the loop readings are, this is why Zs minus Ze = (r1 + r2) method cannot be done. If you do use the (r1 + r2) + Ze = Zs method it has to be stated on your certificate that the Zs readings are a calculated reading.

 

[Richard]

Hi, We had a very similar occurance when we were testing a large college. We use Fluke 1653 testers (error 5 dennoted excessive noise) and had never come accross it before. It was always when we were loop testing (Ze and Zs), and seemed perticularly apparent on one phase. The only explination we could come up with was a large amount of florescent lighting. Richard