harmonics

[Sintra]

this question came up in a 2382 paper and i think the answer is A which ive gathered from App 11. however the answer paper states B as the answer.thanks
A TP&N system supplies an office with IT equipment and has high harmonic currents. How would the effects of harmonic distortion be controlled.
a)increse the size of neutral
b)add surge protection
c)fit a time delay RCD
[FONT=&quot]d)cannot be controlled[/FONT]

In the original question does it mention a half size neutral conductor or is this the full question that you have posted?

 

[joe_berks]

fair play... as i say i might be chatting waffle but was all off the top of my head.
you are right about eddy currents.
what is it im thinking about then when you do have to increase the neutral size? im sure i remember that when i done the 17 ed exam.

 

[pevvers]

what is it im thinking about then when you do have to increase the neutral size?

Harmonics!!!

 

[havoone]

In a tp&N installation servicing an office with IT equipment and a high harmonic disturbance. how would the harmonic influence be combated

This is the question in its etirety.I have since learned that the question was in fact constructed by a lecturer not C&G, so may not be constructed properly.

However I can see that there seems to be quite a number of possible solutions including incresing the neutral.
If i can ask the question, Does Appendix 11 of BS7671 suggest increased neutral as a method of combating harmonics. I cant see anywhere that it mentions surge protection.I am purely trying to stick with these regs.
and thanks again for everyones input

 

[netblindpaul]

You need to increase the neutral size IF the sum of the harominc currents in the neutral conductor can exceed the sum of the fundemental currents in the phase conductors.
Paul

 

[Davey101]

What about running two neutrals, i.e. in parrallel?
Have seen this done before.