Generator

[Andy™]

:^O post #49

seems Steptoe is on his own!

 

[steptoe]

[quote name='Andy

 

[philbas]

[quote name='Andy

 

[steptoe]

[quote name='Andy

 

[Sidewinder]

Right,

NOW I see what steps is on about, IF the IP gets a shock from a live conductor it is following the bodily resistance to true earth. Thus the fault current is flowing through this (virtual as steps says & I'm not going to argue this for now) TT system.

The supply earth is rodded, TT, or TN, no issues. That is how it is.

The "confusion" is at the consumers end.

As I understand it steps is saying TT it because then any potential shock current will flow as a potential divider between the IP & the TT rod.

Am I getting your point so far?

 

[Andy™]

it can vary,it doesnt vary on TT or TNS from DNO because it is rodded and earthed throughout,but a TNS from a genny is magically different than that of DNO?

you are talking about an installation that has no rod at star point.i have always stated that a rod must be installed at star

so it cannot have a common earth point,

if the genny is not earthed, (possibly on wheels/a lorry) then it will be insulated, and therefore have absolutely no reference to general earth, it would almost be similar to TNCS without the S. both N & E are the same potential.

if genny is on trailer and insulated by rubber wheels, then it could be very dodgy... trailer to ground would be IT, but installation may be TN

my red

 

[Andy™]

how do you work that out for direct contact?

i said fault to metallic case...

if, regardless of it being TT or TNS, if you touch a live part (direct contact), fault current will always go through you, ground, rod and back to star, and trip the RCD

 

[steptoe]

[quote name='Andy

 

[steptoe]

[quote name='Andy

 

[Andy™]

if you still cant understand how a direct contact fault occurs then you really should think about becoming unemployed.

im well aware of how a direct contact fault occurs....

and the result will be the same for TT, TNS & TNCS

but the point is, i fail to see how a TN installation becomes a TT when you get a shock....

 

[Andy™]

 

[steptoe]

[quote name='Andy

 

[philbas]

Very confused now

We had a supply from the DNO, it went (bill not payed)

so we put in a genny to replace it.

Other than the fact that the genny is in our control, how does this alter things.

Surley everything else stays the same unless the earthing has changed

 

[Sidewinder]

Guys this is getting heated, i can appreciate why but lets cool it.

We are now moving into FMEA's Failure Modes & Effects Analysis.

We have an engineered system.

When operating as designed there is no problem.

Steps is suggesting, sorry Steps, I have just realised that i did not capitalise my previous posts correctly.

Steps is suggesting that in a direct contact failure mode the effect on the system is to deliver the fault current via the same modus operandi of a TT system.

Steps?

 

[Manator]

Please be aware that many people learn from these debates. Fundemental beliefs and hard hitting facts do not always go hand in hand.

If you are going to contribute to the debate stay cool and state your case, respect is earned when you can debate without malice

 

[philbas]

Can we agre the Genny need to be earhthed at the star point ?

 

[Sidewinder]

YES

 

[philbas]

Sow then it becomes a point of supply,ie it repalces the DNO's point of supply

 

[philbas]

So if the orginal source of supply was TT, then its still TT, unless we supply an earth from the Genny, or if it was tnc (-s) its still that if we supply the earth

only difference is, is our new earth as good as the old one?

 

[philbas]

I phrased that badly