Cant really explain it any better or clearer than this.
Firstly my apologies for interrupting a thread. I'm an avid reader of forums but not well versed with any etiquette .
I have particularly sought to seek your advice as I deeply respect your knowledge and understanding of the 2394/5 examinations.
I am undertaking the 2394 written exam in a few weeks and have been just finalising my revision notes. I have made use of the published Chief Examiners Reports which do tend to point out the basic errors students make.
However one note from a report (Aug 2014) is confusing me, and I would be grateful for your thoughts.
To quote from the report :-
"Candidates were asked to explain the expected pattern of test results when carrying out an earth fault loop impedance measurement at each socket-outlet on the ring circuit. Many candidates incorrectly believed that the results would be the same at each socket-outlet. "
Please correct me if wrong but I have been taught that a correctly installed ring circuit will have substantially the same (R1 + R2) value at each socket outlet (within 0.05ohms). The only exception would be where the ring contains a spur , the (R1 +R2) being marginally higher at this point , proportional to the extra cable length.
I have also been taught that the following calculation is used to calculate Zs , Zs = Ze + (R1 + R2). I'm fully aware of ambient temperature and conductor operating temperature considerations for verification but lets keep it simple for now. Ze is a constant, as mentioned (R1 + R2) should be substantially the same for each outlet so my question is why would it not be conceivable to expect substantially the same Zs values ?
Again my apologies for interrupting this thread, I would be really grateful for thoughts .