Understanding breakers and RCD, un-vented cylinders

[ipf]

Hi, i started with a specific "dictionary definition",that is Oxford variety,and not Google and it says,what i said.

I have always had a problem with the term "short circuit",and this is the only reason i am whining on

I think it stems from me nan,who as a kid,would describe absolutely any deviation from correct operation,in machinery or person,as a "short circuit" ....that,and general grumptitude

.....and I always thought a 'short circuit' was less than 5m in length....you live and learn, eh!

 

[I2C]

Hi, i started with a specific "dictionary definition",that is Oxford variety,and not Google and it says,what i said.

I have always had a problem with the term "short circuit",and this is the only reason i am whining on

I think it stems from me nan,who as a kid,would describe absolutely any deviation from correct operation,in machinery or person,as a "short circuit" ....that,and general grumptitude

This definition is taken directly from the Wiring Regulations (BS7671 17th Edition Amendment 3). I'm not sure what an "Oxford Dictionary" states, but regardless the IET publications are the proper reference.

However I do understand, many people use the term 'short-circuit' incorrectly / naively to describe faults. Everyone has done at some point (including myself).

I once worked with an electrician once who told me that using a AVI (Approved Voltage Indicator to GS38) between line-neutral would create a short-circuit! With this said, I promptly explained that the AVI that I was using had an internal resistance of 200kOhms which results in a perfectly safe and easily calculated current-flow of around 1mA. And yes, I'm aware that I'm sad enough to read the datasheets.

In fact, when I first began training as an electrician I honestly believed that transformers, electromagnets, and electric-motors where a short-circuit due to their measured low resistance! I seriously couldn't understand why circuit-breakers didn't trip when a motor was switched on. Of course, this was before I understood inductive-reactance, and therefore impedance.

My advice - nobody knows everything (including myself) and mistakes result in improved knowledge. I've made comments here which where naive and quickly corrected by other members, for which I have remained humble and learned from them. Don't be put off, no question or comment is silly because we all can only improve. That's why I love this forum, because everyone is so understanding and respectful, with all members having an incredible combined-knowledge.

 

[davesparks]

.....and I always thought a 'short circuit' was less than 5m in length....you live and learn, eh!

A short circuit is one where the normal circuit load is bypassed by a low resistance path where current can flow from one phase to neutral or to another phase.
Anything which results in the flow of current to earth is a fault

 

[I2C]

A short circuit is one where the normal circuit load is bypassed by a low resistance path where current can flow from one phase to neutral or to another phase.
Anything which results in the flow of current to earth is a fault

With all due respect, your definition of a 'short-circuit' is almost correct, without using correct terminology. I've given the indisputable definition directly from the Wiring Regulations (BS7671 Amendment 3) regarding short-circuits previously for reference.
You're correct in mentioning that a short-circuit is between live-conductors (live conductors meaning the conductors which carry current under normal conditions), between line-neutral / line-line with 3-phase systems, however it's important to consider the total opposition to current in an AC circuit (impedance), rather than simply the resistance.

Also, earth-faults are distinctly different from short-circuits. By their very nature, they require additional considerations (such as the requirement for 'additional protection', with the voltage represented as U0, and varying depending on the earthing-system) amongst other factors.

 

[electric al]

Looking at the picture of the stat I would say there should be a reset button underneath that sticker stating ' factory seal '

 

[ipf]

A short circuit is one where the normal circuit load is bypassed by a low resistance path where current can flow from one phase to neutral or to another phase.
Anything which results in the flow of current to earth is a fault

Thanks for the quote and info, dave. You really do live and learn

 

[camerabloke]

.....and I always thought a 'short circuit' was less than 5m in length....you live and learn, eh!

I thought short circuit was something to do with Jonny 5