3ph + E Zs calculation?

[Strickers]

Can anyone tell me how to calculate the zs in a 3ph+E installation as my tester will not give me a reading. I've looked into it and a special loop tester is needed, if this is right?

Thanks Paul

 

[ajelec10]

are you sure you know what you mean? to get a zs on a 3 phase system you just test brtween each phase and earth witch is only 230v and record the highest reading no special testers required. if you need to calculate the psc accross the phases then get a zs accross phase and nutural work out the current usins 230v then times it by 1.73205
regards
aj

 

[Strickers]

The problem is there is no neutral and my fluke 1652 wont test without a neutral.

 

[ajelec10]

Some testers you can put the nutural and earth leads together then test the phases that should work

 

[Strickers]

I could just use Ze + R1R2 x 1.732205 but i like to take a measured reading.

 

[dkent5]

You may be trying to test three phase and earth with a three lead instrument? If so, both the neutral and earth crocs need to be connected to the earth bar and the line test lead to the phase you are testing and as AJ says record the highest reading of the three phases. Divide 230 by your lowest reading to give you the worst case scenario of prospective earth fault current on one phase and multiply it by 1.73205 (square root of 3) to give the phase to phase value of PSCC.

 

[Strickers]

i've tried with neutral and earth leads together on the earth but it doesn't work

 

[ajelec10]

Always buy megger lol

 

[dkent5]

I use the same tester and when this doesn't work I normally get ERR5 when the earth and neutral are not connected at the secondary side of the transformer or the earth is not connected at all! You should check this.

 

[Strickers]

Bascially there a set of large floods for a sports pitch that have been imported from America. I was testing from the isolator with lights turned off, should i test with the isolator on? This will put power to transformer on pole.

 

[dkent5]

You need the supply on to perform a loop test and loads should be removed. The fluke 1652 does not like doing earth loop impedance tests on circuits under load, whereas the old robins would do it.

The circuit must be energised to perform the loop test with loads removed. The Fluke 1652 sometime won't test circuits under load conditions.

One to remember is that the Fluke 1652 will not loop test 110v circuits, you will require a special tester for this. I'm assuming that the American lighting is 110v.

 

[ian.settle1]

Bascially there a set of large floods for a sports pitch that have been imported from America. I was testing from the isolator with lights turned off, should i test with the isolator on? This will put power to transformer on pole.

Would be a very good idea to switch on the isolator as if not the is no power to do a Zs test.

 

[Strickers]

My head was completly fried on this one, i had all of it set up right borrowed another fluke tester and it worked fine. So my tester is obviously broken, and it's not long been in for calabration. Cheers for all the help guys