HELP! calculating ze

[Ste69]

Is it possible to calculate Ze?

I am in the middle of an assignment, and have this question to answer.

When confirming automatic disconnection of the supply it is necessary to determine the external earth fault loop impedance(Ze) of the system. State three methods by which this can be achieved.

i have 2, inquiry and measurement (my answer is a little more in depth lol)

to my problem, i want to say calculation and the tutor has said this is correct BUT when i look into it i can not find the calculation! i can work out (Zs) i.e Zs = Ze + (R1 + R2)

so am i right in thinking the question is wrong? or am i being an idiot and missing something here?

sorry for the long winded question.

 

[GLENNSPARK]

lets not forget here that in general characteristics of supply it would be the nominal value of Ze that was put down.....
so for a TN-S its .8......TN-C-S its .35

its the schedule of tests that require a measured value of Ze

 

[ArseyDee]

lets not forget here that in general characteristics of supply it would be the nominal value of Ze that was put down.....
so for a TN-S its .8......TN-C-S its .35

its the schedule of tests that require a measured value of Ze

Sorry Glenn, I don't agree with that. Supply Characteristics Ze can be by measurement. That's the way it's worded on the IET Cert anyway....

 

[GLENNSPARK]

Sorry Glenn, I don't agree with that. Supply Characteristics Ze can be by measurement. That's the way it's worded on the IET Cert anyway....

so...if your putting measured values of Ze down in the supply characteristics section....why bother with the box in the schedule of tests?

 

[ArseyDee]

so...if your putting measured values of Ze down in the supply characteristics section....why bother with the box in the schedule of tests?

I agree, but the Supply Characteristics for Ze definitely says "by enquiry or measurement".

 

[GLENNSPARK]

I agree, but the Supply Characteristics for Ze definitely says "by enquiry or measurement".

so...what would it be by enquiry then?

 

[GLENNSPARK]

let me give you a pointer:

the general characteristics section is for the design....and as such nominals would be used...

THATS why there is a box for measured values on the schedule of tests

 

[ArseyDee]

That's your opinion. I'm just stating what is actually printed on the IET Certs.

 

[Zebra Stripe]

I put down the measured Ze (when possible to test) and maybe a Zdb with an asterix when not and note it somewhere on cert. I think the part on the SoT is for a Zdb when you have perhaps a submain etc...but I suppose it depends on which or whos cert your filling out, they all seem to be slightly different.

 

[ArseyDee]

I put down the measured Ze (when possible to test) and maybe a Zdb with an asterix when not and note it somewhere on cert. I think the part on the SoT is for a Zdb when you have perhaps a submain etc...but I suppose it depends on which or whos cert your filling out, they all seem to be slightly different.

My next point was going to be along those lines. Thanks.

 

[GLENNSPARK]

I always put the nominal value in regards to the earthing arrangements in the supply characteristics box..

the measured value goes in the schedule of tests...

 

[Zebra Stripe]

Hey does it really matter as long as the CERt can be interpreted by someone else?

 

[ArseyDee]

Hey does it really matter as long as the CERt can be interpreted by someone else?

Agreed.

 

[Silly Sausage]

Hey does it really matter ................

No one reads them apart from SECTION E and it contains the word ....

Satisfactory!

 

[Zebra Stripe]

Hey I love to read other peoples certs, unfortunately they seem to be very rare in most occassions

 

[Silly Sausage]

Hey I love to read other peoples certs.

You enjoy reading works of fiction then?!