Trainee Question for Inspection and testing

[dave440]

Hi, part of my coursework is asking me to verify a series of test results.
The task is to explain any problems or deviations.

The results I have are related to a domestic ring circuit.
2.5mm cable.

the results I have are

Line1 : r/1, 0.27
r/n : r/n, 0.28
r/2, 0.45

My R1+R2 is 0.18

and my Zs is 0.34

I have not measured or calculated any of these values myself as they come from an exam question.

my task is to explain any problems with it, However I don't see anything wrong with them, am I missing something?

this is part of my homework and I'm getting a little desperate from some help.

 

[Paul.M]

Dave we have a Training section set up just for people like you with questions like this. You have to apply though here:- http://www.electriciansforums.co.uk/apply-gain-access-trainee-only-forum/

Lets leave this thread to run and see what every one thinks. I bet your Ze is 0.14

 

[Leesparkykent]

Hi, part of my coursework is asking me to verify a series of test results.
The task is to explain any problems or deviations.

The results I have are related to a domestic ring circuit.
2.5mm cable.

the results I have are

Line1 : r/1, 0.27
r/n : r/n, 0.28
r/2, 0.45

My R1+R2 is 0.18

and my Zs is 0.34

I have not measured or calculated any of these values myself as they come from an exam question.

my task is to explain any problems with it, However I don't see anything wrong with them, am I missing something?

this is part of my homework and I'm getting a little desperate from some help.

2.5t+e with 1.5mm cpc?

might be be worth asking one of the mods for access to the trainee section as well mate.

 

[dave440]

Yes, the standard flat twin and earth.

 

[Paul.M]

2.5t+e with 1.5mm cpc?

might be be worth asking one of the mods for access to the trainee section as well mate.

Whoops, I replied to this but I hit the wrong button and no one else could see it until now.

 

[dave440]

Yes, will, however I need to leave my computer for about i hour, and I will return, I was hoping someone would be able to help me urgently, as I'm back at college tomorrow.
(everything at the last minute as usual!)

 

[Pete999]

Hi, part of my coursework is asking me to verify a series of test results.
The task is to explain any problems or deviations.

The results I have are related to a domestic ring circuit.
2.5mm cable.

the results I have are

Line1 : r/1, 0.27
r/n : r/n, 0.28
r/2, 0.45

My R1+R2 is 0.18

and my Zs is 0.34

I have not measured or calculated any of these values myself as they come from an exam question.

my task is to explain any problems with it, However I don't see anything wrong with them, am I missing something?

this is part of my homework and I'm getting a little desperate from some help.

Have they told you what type of OCPD is being used?

 

[Leesparkykent]

Yes, the standard flat twin and earth.[/QUOTE

0.27+0.45=0.72, 0.72/4=0.18

0.27x1.67=0.45

Looks fine to me, but I'm sure I'll be told I'm wrong lol.

 

[dave440]

The Over current device is a type B MCB 32 Amp.

the Ze (which I should have posted) is 0.17

 

[dave440]

Dave we have a Training section set up just for people like you with questions like this. You have to apply though here:- http://www.electriciansforums.co.uk/apply-gain-access-trainee-only-forum/

Lets leave this thread to run and see what every one thinks. I bet your Ze is 0.14

The Ze I have been given is 0.17

Thats one of the things I'm suspecting also.

 

[ImpededLoop]

The Ze I have been given is 0.17

Thats one of the things I'm suspecting also.

Although that's the Ze, there may be parallel paths from the bonding etc, which bring the Zs down below the expected value, hence the 0.14 ohm mentioned earlier.

Are there any more details for this question other than what you've already told us?

 

[ImpededLoop]

Yes, the standard flat twin and earth.[/QUOTE

0.27+0.45=0.72, 0.72/4=0.18

0.27x1.67=0.45

Looks fine to me, but I'm sure I'll be told I'm wrong lol.

This looks sound to me.

 

[TJ Anderson]

I would have bet your Ze at 0.16
As this is theoretical and not real, ZS-(R1+R2) = 0.16
As already said, on a real installation you would have parallel paths also.
There is also an allowance of 0.05 in your leads so it is all perfectly in order in my opinion as within 0.01
The 0.17 Ze may have been to throw you slightly with the 0.05 allowance

 

[Pete999]

I would have bet your Ze at 0.16
As this is theoretical and not real, ZS-(R1+R2) = 0.16
As already said, on a real installation you would have parallel paths also.
There is also an allowance of 0.05 in your leads so it is all perfectly in order in my opinion as within 0.01
The 0.17 Ze may have been to throw you slightly with the 0.05 allowance

Thought the rule was to null your leads before any resistance testing???

 

[TJ Anderson]

Thought the rule was to null your leads before any resistance testing???

Yes definatly. Even with the leads nulled, there is still a 0.05 margin.