Continuity of cpc on 2 core SWA cable

[ajay123]

Hello I was wondering if anyone could help me on what is the most appropriate method to test continuity of cpc on a 2 core steel wire armoured cable to a distribution board.

 

[Darkwood]

Welcome to the forum ajay123

I've relocated your thread to the correct section, if you are currently on a active training course you may benefit from our trainee section, just apply providing all the required info requested.

 

[Simonslimline]

Method 1 or method 2 depending on distance i guess.

If method 1 then do it between line and neutral first and half the reading to get a value for R1.

 

[Octopus]

Hum.... How do you think you would do it on 2 core SWA ?

 

[Simonslimline]

Maybe worth noting that the op is a trainee according to the profile.

 

[Octopus]

Maybe worth noting that the op is a trainee according to the profile.

Which is why I asked the question .....

 

[Risteard]

Method 1 or method 2 depending on distance i guess.

If method 1 then do it between line and neutral first and half the reading to get a value for R1.

Not sure how that would help you verify cpc continuity unless I'm misunderstanding you.

 

[Simonslimline]

Not sure how that would help you verify cpc continuity unless I'm misunderstanding you.

method 2 may not be a viable option due to distance etc.

In order to get a value for the armour being used as the cpc you would need a value for R1 first to subtract from the reading of the R1+R2.

Am i missing something?

 

[Richard Burns]

I would say that you may need to check that the armour gland is not still connected to other metalwork that may provide an alternative path for your measurement.
Other than that as simonslimline says measuring R1+R2 will record continuity of the armour, and subtracting half the R1+Rn value would give you a resistance value for the cpc.
On average the resistance of the armour would generally be about 1-1.5 times the R1 resistance for 1.5mm² cable and drop down to about 1/3 of the R1 resistance for 25mm² cable.

 

[ajay123]

But how would I connect line and the steel wire together at one end of the cable, and then after I can just put one test probe on the gland on the other end of the cable and the other probe on line

 

[Simonslimline]

Just use a bit of cable with some croc clips on each end. A jump lead type thing i guess.

 

[Simonslimline]

But how would I connect line and the steel wire together at one end of the cable, and then after I can just put one test probe on the gland on the other end of the cable and the other probe on line

Are you familiar with the methods i mentioned?

Method 1 and method 2.

Invest in a copy of guidance note 3, it would be beneficial to you mate.

 

[Risteard]

In order to get a value for the armour being used as the cpc you would need a value for R1 first to subtract from the reading of the R1+R2.

Fair enough, but we're not actually interested in the phase conductor resistance but simply that we have adequate continuity on the cpc. But I realise that knowing what resistance the cpc should be for the length expected is important.

 

[Simonslimline]

Fair enough, but we're not actually interested in the phase conductor resistance but simply that we have adequate continuity on the cpc. But I realise that knowing what resistance the cpc should be for the length expected is important.

Using method 2 long lead test would be a simpler way of achieving this in all fairness. However if the SWA is a long distance then this method might not be viable, hence using method 1 Between Line & Neutral to get a value to subtract from the method 2 result between Line and CPC/armour.

 

[Simonslimline]

Edit of post above, the last line should read method 1, not 2.