2330 303 written paper

[hospital]

Good evening ladies and gentlemen,has anyone recently taken the 2330 303 written exam,the fault finding and rectification one if so any pointers would be most welcome.

Thankyou,Peter.

 

[derek preece]

I got a distinction in my written exam, well chuffed

 

[i=p/u]

when working out the Zs ,say you have 0.28 as Ze, R1 +R2 values , say it was a ring circuit in 2.5/1.5mm and was 63 meters long . is this correct 19.51 x 63 / 1000 / 4 = 0.31 + 0.28 = 0.59 as Zs????

 

[derek preece]

when working out the Zs ,say you have 0.28 as Ze, R1 +R2 values , say it was a ring circuit in 2.5/1.5mm and was 63 meters long . is this correct 19.51 x 63 / 1000 / 4 = 0.31 + 0.28 = 0.59 as Zs????

I assume you are doing (r1+r2)/4 end to end resistance values of the line and the CPC of the ring (as opposed to R1+R2 divided by 4) in which case I think it is correct, but I don't have my OSG with me at the mo.
But I believe measured Zs can have a lower value due to parallel paths

 

[i=p/u]

cheers i think , if im correct, , am i right in dividing by 4 as is a ring...

 

[derek preece]

"the resistance between line and earth is measured at each socket. the readings obtained... will be substantially the same and the value will be approximately one-quarter of the resistance of the line plus cpc loop resistances, (i.e. (r1+r2)/4"
quote from pg82 OSG so I think you are right

 

[i=p/u]

i have good idea of ring testing, but im just playing with sums in my head, as i do, as im a pull cord gack... naw but if you were working out lengths of circuits before installed..

 

[derek preece]

Just had to do some for my first design job, working out Zs for appropriate protective devices, I'm hoping I got it right because I'm installing it on Tuesday, just had to do Ze and pfc psc tests today. But I am going to be triple checking my calculations and relevant regs