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Earth fault loop impedance understanding
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<blockquote data-quote="SPECIAL LOCATION" data-source="post: 503046" data-attributes="member: 250"><p>Your thoughts are correct....</p><p></p><p>But also you have to allow for how good the connection is between your meter probes/clips and the cable you are testing...</p><p></p><p>Think about the numbers you are getting, also think about what values you get if you measure continuity on just your meter leads before they have been zeroed.</p><p></p><p>AND.. vitally important you need to keep an awareness of what values you are expecting to read, proportional to the cable conductor sizes..</p><p></p><p>e.g. If a reading taken a couple of meters up a circuit is similar to, (or less than), a reading taken at the origin, that can be just due to the connection of your meter leads..</p><p></p><p>But if you were getting a lower reading say 60m away up the circuit then something may not be right?</p><p></p><p>your values of 0.24 and 0.19 is a difference of 0.05..</p><p></p><p>If this 0.05 was part of a 2.5/1.5 T&amp;E radial..</p><p></p><p>then 0.05 = approx 2.6m of cable!! </p><p></p><p>Have a look at the resistance values for copper cables in Appendix I of the OSG..</p><p></p><p>and consider if your differences equate to a gnats whisker of cable or a significant length..</p><p></p><p> Guinness </p></blockquote><p></p>
[QUOTE="SPECIAL LOCATION, post: 503046, member: 250"] Your thoughts are correct.... But also you have to allow for how good the connection is between your meter probes/clips and the cable you are testing... Think about the numbers you are getting, also think about what values you get if you measure continuity on just your meter leads before they have been zeroed. AND.. vitally important you need to keep an awareness of what values you are expecting to read, proportional to the cable conductor sizes.. e.g. If a reading taken a couple of meters up a circuit is similar to, (or less than), a reading taken at the origin, that can be just due to the connection of your meter leads.. But if you were getting a lower reading say 60m away up the circuit then something may not be right? your values of 0.24 and 0.19 is a difference of 0.05.. If this 0.05 was part of a 2.5/1.5 T&E radial.. then 0.05 = approx 2.6m of cable!! Have a look at the resistance values for copper cables in Appendix I of the OSG.. and consider if your differences equate to a gnats whisker of cable or a significant length.. Guinness [/QUOTE]
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