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Topic Title: Zs on a single circuit
Topic Summary: How do i measure the Zs of a single circuit.
Created On: 01 February 2013 01:57 PM
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 01 February 2013 01:57 PM
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JBrown123

Posts: 1
Joined: 01 February 2013

Can anyone please explain to me how to measure the Zs of a single lighting circuit ? not the whole installation. thanks!
 01 February 2013 02:21 PM
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Avatar for OMS.
OMS

Posts: 19747
Joined: 23 March 2004

Find the end (or worst favoured branch) and measure from there if you want a live test direct reading with a EFLI tester

Or do the same by measuring the relevent phase and CPC dc resistance and calculate it with knowledge of the impedance external to the installation.

Or calculate it from knowledge of the cable size and length and again with knowledge of the external impedance.

Regards

OMS

-------------------------
Failure is always an option
 01 February 2013 06:00 PM
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dg66

Posts: 1675
Joined: 11 January 2008

The third option mentioned by OMS should be used in combination with either of the other two options mentioned.

-------------------------
Regards

Dave(not Cockburn)
 01 February 2013 06:22 PM
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Zs

Posts: 2966
Joined: 20 July 2006

Wow.
 01 February 2013 06:29 PM
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Jaymack

Posts: 4668
Joined: 07 April 2004

Originally posted by: JBrown123
Can anyone please explain to me how to measure the Zs of a single lighting circuit ?

Measure R2 at light switches and at lighting points, to determine the worst case for the circuit, take this highest value and either test there for Zs or use in the calculation.

Regards
 01 February 2013 06:45 PM
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daveparry1

Posts: 6239
Joined: 04 July 2007

I don't quite know why you need to measure the Zs if you dont know how to do it? What i'm trying to say is that a Zs figure is only normaly used by an electrician to check the safety of a circuit!

Dave.
 01 February 2013 11:14 PM
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Martynduerden

Posts: 3211
Joined: 13 July 2008

Originally posted by: Zs

Wow.


Good init!

-------------------------
Regards

Martyn.

Only a mediocre person is always at their best



www.electrical contractors uk.com
 01 February 2013 11:33 PM
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John Peckham

Posts: 7509
Joined: 23 April 2005

JBrown123

Welcome to the forum. Is this a test question you have been asked to answer by your college lecturer for Monday morning? If so we may need to give you a different answer to stop you falling in to an evil trap set by a wicked person. Lecturers of course don't live in the real world but some sort of academic lah lah land!

Dooh I might have just shot myself in the foot.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 02 February 2013 07:26 PM
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AJJewsbury

Posts: 11553
Joined: 13 August 2003

Measure R2 at light switches and at lighting points, to determine the worst case for the circuit

Presuming L follows the same route as PE ... which isn't necessarily the case for a lighting circuit
- Andy.
 04 February 2013 01:19 PM
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BigRed

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Joined: 10 November 2006

measure Zs? with a tape measure...:-) Gives me the distance to avoid the curled up hand hurtling towards my arm.....
 04 February 2013 03:17 PM
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zeeper

Posts: 1411
Joined: 11 July 2008

measuring the relevent phase and CPC dc resistance and calculate it


Hes just lost three points for calling the line conductor a phase conductor.
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