Earth fault and open circuit

[daws124]

Could anyone explain a likely cause for each of those?

Is the cause of an open circuit and broken conductor? Help would be appreciated. Can't find any info on this :/

 

[Tridentsystems]

Could be

 

[Patto]

Can you give more info?

 

[trev]

Have a think about this Daws it's fairly basic stuff, I'm guessing this is all new to you though. An open circuit could be caused by a broken conductor, it could be caused by a switch not operating (deliberately trying to keep it simple)
What's your thoughts on what an earth fault is?

 

[Richard Burns]

As Trev says try and think about what is meant by an
Earth fault: once you know the description of an earth fault then it should be come clear how can occur.
Open Circuit: if this is the disconnection of a continuous circuit path from line to neutral then where and how can this occur, think of items you know about and where such a fault could happen.

 

[daws124]

Thanks for the help lads,got there in the end. I'm now struggling like he'll with the 2365 303/304/305 assignments!!! So close to quitting as I just don't know where to start with them!!

 

[trev]

Don't quit! post up what you're struggling with and have a go at the answers, you'll get the help you need

 

[daws124]

Thanks I appreciate that. Struggling with why we do the test sequence before putting a install back into service? I know the tests "cripplers" but don't know why we do it in that order?? Hmmm

 

[telectrix]

as a start, it's pointless doing an insulation ( megger ) test before ensuring that there is circuit continuity, else you would be testing only part of a circuit if there was a break somewhere. likewise, live tests must not be done before all dead tests confirm that the circuit is safe to be energised.

 

[daws124]

Thank you for that help,makes sense,quite obvious really when someone explains!! Hero!

 

[kingeri]

Bless ya, keep at it and you'll get there!

 

[daws124]

I'm trying mate! Appreciating the help!

 

[Silly Sausage]

Get your fundamental basics nailed first.
Ohm's Law, Kirchhoff's etc etc...burnt into your mind so you don't have to think about them.
Bit like walking into a pub, you never think about how to ask for a pint. Well I hope not!

 

[daws124]

Yeah very true! Never forget how to do that! Ha

So if I was to add another circuit to an installation the insulation resistance between the live conductors would decrease as there is more cable for the current to leak?? Am I thinking right? If so that would be the same for a longer length of cable?!

 

[telectrix]

nope. picture an extra circuit added is in parallel to the existing circuits. impedances in parallel decrease the overall impedance. longer cable would increase resistance.

 

[Richard Burns]

But a longer cable has the capability to reduce the insulation resistance because of a larger surface area for leakage. Probably not overly significant over short distances and certainly the actual end to end resistance of the cores would increase.

 

[SirKit Breaker]

Tel has hit the nail on the head really.

If you Ins Res a circuit, you will get a good result even if there is a break in the circuit, as it will only test up to the point of the break.

So you carry out continuity, usually R1+R2 method, to confirm that the circuit is continuous.
If you are working on a ring, then you would follow this by doing Ring continuity.
Then you would IR the circuit.

Dead test completed.

Job done.

I would advise you get hold of IET Guidance note 3, it explains in simple to understand terms with illustration etc all things testing, and will pay for itself in no time. Even the experts and more experienced of us who do this day in and day out, and in my case i teach it, there isn't a week goes by where i don't need to refer to GN3, and I've been doing this all my life.

Cheers..........Howard

 

[telectrix]

true, howard. nobody can remember everything. what was the question, i forgot.

 

[Geordie Spark]

true, howard. nobody can remember everything. what was the question, i forgot.

Don't worry too much about it Tel ....... a bit of memory loss is to be expected at our age. :wheelchair::wheelchair:

 

[telectrix]

doc gave me some tablets for it, but i keep forgetting to take them. hmm, take what? my brain hurts.

 

[Geordie Spark]

doc gave me some tablets for it, but i keep forgetting to take them. hmm, take what? my brain hurts.

Aye .... it's a bugger ........ I spent the best part of two hours chasing Tidyboiler around the bedroom and when I finally caught her I couldn't remember why I had been chasing her.

 

[tidyboiler]

Aye .... it's a bugger ........ I spent the best part of two hours chasing Tidyboiler around the bedroom and when I finally caught her I couldn't remember why I had been chasing her.

Come upstairs, and I'll remind you.......... :smilewinkgrin:

 

[Silly Sausage]

I don't believe he could chase for 2 hours. 2 minutes maybe...:smilielol5:

 

[Geordie Spark]

I don't believe he could chase for 2 hours. 2 minutes maybe...:smilielol5:

My Zimmer frame has just been serviced .....

 

[telectrix]

but has TB been serviced, that is the question.

 

[Silly Sausage]

He never caught her!

 

[Geordie Spark]

He never caught her!

I did ................ but only after she accidentally stepped in the gazunder and got her foot stuck in it.

 

[telectrix]

hope it was empty at the time. otherwise would give a whole new meaning to golden rain.

 

[tidyboiler]

hope it was empty at the time. otherwise would give a whole new meaning to golden rain.

I've seen the video! :rockon2:

 

[Geordie Spark]

I've seen the video! :rockon2:

Seen it ... you bloody starred in it !!!!!