ring main query

[bobby101]

hi all i want to know if its possible to obtain r1 and rn and r2 results by calculation by only having the R2 reading and zs reading
i am unsure if this is possible any pointers would be great for a ring main circuit, i can judge the approximate length if this is a required factor

 

[telectrix]

these should be measured before energising thew circuit to ensure you have continuity from end to end of the ring final circuit (not ring main)

 

[bobby101]

yeah thanks for the advice but it does not answer my question thanks

 

[johnboy6083]

you shopuld never have to do this, and i cant see why you would want to. If its just a theorietical excersize, then it is possible to get rough figures.

R1 + R2 can be gained from using Zs= Ze + R1 + R2. You should never use this method to gain results for test sheets though.

R1 can be gained from taking R2 away from R1+R2. Rn should be the same size conductor as R1, so the resistance should be roughly the same.

r2 end to end can be roughlyu calculated by R2x2
r1 is roughly R1x2
Rn should be roughly the same as R1


just to reiterate, this is only a theoretical excersize, and not one that should be used for gaining Test results.

 

[sedgy34]

hi all i want to know if its possible to obtain r1 and rn and r2 results by calculation by only having the R2 reading and zs reading
i am unsure if this is possible any pointers would be great for a ring main circuit, i can judge the approximate length if this is a required factor

whats your reason for your question (you not being lazy on testing are you lol)

 

[telectrix]

as above. you can't get a reliable reading by "back calculation" as Zs is measured live, with parallel paths connected.
( bonding for 1). this would give you a false value for R1.

 

[Litttle Shonet]

R1 can be gained from taking R2 away from R1+R2.

Surely if your taking R2 away from R1 + R2 to get R1, you already know R1!!!

 

[johnboy6083]

Only R1 +R2 from using the Zs-Ze. So yes you do know it (very roughly) but only from calculating it.

 

[telectrix]

if you have measured R2, then if same size conductors, R1=R2. with T/E, where the cpc is a smaller csa, then R1 can be calculated by multiplying/dividing by the csa ratio.

 

[johnboy6083]

althougn hwt we are doscussingis purely theoretical, and niot tobe used for gaining results, it can be used to see what results should be expected. If your calculated figures are massivley different from your measured results, then something may be wrong, and it may give you an early indication of a problem.

 

[GLENNSPARK]

yeah thanks for the advice but it does not answer my question thanks

Bobby.....testing of ring finals is a 3 stage test..ok....so forst its continuity of ring..r1 r2 rn...yes?.....ok then its R1+Rn.....then R1+R2...this confirms that you have a true ring...no open circuit and no ring within a ring scenareo.....it also confirms polarity...this is the way we do continuity of ring finals.....so why are you wanting to rock the boat?....

 

[Amp David]

yeah thanks for the advice but it does not answer my question thanks

Alright then, NO!