tncs

Dm7192 · Jun 27, 2011

Just a general question, how is it when we touch live to earth or there is a short circuit between live and neutral there is an electrical explosion or some sort of reaction however when we use a tncs earthing systems should this not happen as the earth & neutral are combined therefore any return current in the neutral will short with earth, would appreciate it if anyone could explain the theory of this haha?

mattmoo1974 · Jun 27, 2011

A "Load" has a resistance, Earth is the fault path and has very little resistance. Low resistance=100+ amps flow.
You Protective device will only allow a certain amount of current to flow, Thus it disconnects.
You have have a fault between line and Netural(or CPC) you miss the load out IE the current takes the easyest path "pop" MCB goes.

telectrix · Jun 27, 2011

you get the flash due to the high current caused by a low resistance short. as both the N and E are at 0v, nothing happens if N and E short, but shorting L to either will give rise to a large current, causing flash and bang due to nthe conversion of electrical energy to sound and light.

sparks_114 · Jun 27, 2011

Firstly a definition of short circuit: The coming together of two conductors of differing potential with minimal impedance. Now, between Line and Neutral there is a potential difference of 230V in your house. Likewise, between Line and Earthing conductor there is a potential difference of 230V. But, between Neutral and Earthing conductor there is usually no potential difference and being at the same potential cannot result in a short (or any) circuit. Hope this helps too.