Help needed! .. Design question anyone care to help?

[Phil Griffiths]

hello just couple questions regarding my my design exams..

1. A 230V single phase circuit is protected by a circuit breaker with RCD (RCBO). justify witch component part of the device would operate for the following faults ..

a. line to earth fault 2.3 ohms
b. line to neutral fault 0.01 ohms
c. neutral to earth fault negligible impedance
d. an overload approx twice the nominal rating of the device

any idea how to work these out!? if so your help would be much appricated and please could your show me how you did it thanks very much

 

[Wilko]

Perhaps work out the current that will flow in each case. Then look at that current's path and what devices are in that circuit ...

 

[Leesparkykent]

RCD Handbook (Dec 2010) - http://www.beama.org.uk/resourceLibrary/rcd-handbook---dec-2010-.html

This is a good read on how RCD's work.

 

[Phil Griffiths]

Perhaps work out the current that will flow in each case. Then look at that current's path and what devices are in that circuit ...

Thanks for the reply, this is all they have gave me i have no circuit diagrams as such to follow. i have just got the fault current connected to a RCBO & RCD. thank again.

 

[MODECSOFT]

Hi Phil,

Maby you can simulate your example using the free version of ElectricalOM software from here electricalom.com

 

[gazdkw82]

I would first work out the current that flows in each scenario. Then refer to bs7671 for current tripping times and specifications. This and some knowledge on how an RCBO works should be enough to find out which part of the RCBO will trip and why