Extremely High Zs Reading

[stuartc85]

I'm testing temporary site electrics at the moment and I'm abit confused as to why my readings are completely different. When I test my zs using 2 phases and earth my readings come out correct. When I test using phase neutral and earth I'm getting readings over 200 ohms. I'm thinking towards a broken neutral as this site is a demolition site and I can see certain hv cables have been cut (hopefully by the correct people). Any other ideas as to why this is happening?

 

[ProDave]

And what tests have you done to determine if you have a broken neutral or not?

 

[binky]

most temporary site electrics tend to be on a rod. Bit confused as to what you are saying, I could be wrong but shouldn't you be testing each single phase to earth, PFC and Neutral to phase PSCC?

 

[stuartc85]

The company I'm subbing work for have taken over this job from another site temporary firm and it's been installed off the existing earth. I've been sent to test this supply but something's not right here. On my megger I've got L-L test which I was told was the best way to test a 3 phase supply?

 

[ProDave]

But what other tests have you done?

You seem to connect your tester, press a button and write down a reading.

When the reading is not as expected you need to investigate further. What other tests have you done to determine if the neutral is connected or floating?

Start with doing 2 wire tests between each phase and E and each phase and N.

 

[binky]

The company I'm subbing work for have taken over this job from another site temporary firm and it's been installed off the existing earth. I've been sent to test this supply but something's not right here. On my megger I've got L-L test which I was told was the best way to test a 3 phase supply?

so you are testing but don't quite understand what your test gear is doing.

1/Get the manual, read it and understand what you are doing first

2/ You should know how to test in your own right - everyone has their own foibles, be very careful of listening to advice from others, you need to understand what you are doing yourself.

NB to some of the regulars, this guy needs educating, play nicely now :^O

forgot to say Stuart, what you are currently doing is testing 2 things at once as pointed out by Pro-Dave, you need to do single tests to stand a chance of fully understanding what is wrong.

 

[Andy™]

this guy needs educating

yes, maybe a plumber? but not with gas. just water

as above, if you dont know what your actually testing then your not going to get far

and as for the neutral fault, well if it was a lost neutral then you could expect stuff to not work... and depending on the site, you may not be able to use TNCS anyway so a neutral fault will have nothing to do with your Zs. and since your saying Zs is high, whats your Ze? (or at least Zs on other circuits)

 

[binky]

I've had a couple of cases where Neutral was poor, but everything appeared to work as normal.

 

[Manator]

If you have been sent to test this installation as it stands, you have to start from the beginning

Each phase will need to be tested against earth, and against neutral.If you get a high reading from ANY test, other tests have to be carried out to establish what is going on and where the problem is.

You need to know your tester inside out, and how to perform all the tests available.

Go back and start with the basic tests, do not listen to how others do it, they could be doing it wrong and give you bad instruction.

 

[zimmy]

I wonder if the OP is still alive?