View the thread, titled "Touch voltage to earth" which is posted in UK Electrical Forum on Electricians Forums.

Can somebody explain if you had a 230v to earth fault the variables that determine touch voltage of a person to earth and is this voltage less the closer you get to the MET of an installation.

Thanks guys
 
During a fault you will get the supply volts times R2/(R1+R2) relative to true Earth where R1 includes the supply phase impedance, and R2 includes the supply ground.

But it is complicated by the other aspects such as any water/gas bonding to metallic pipes that might raise the local earth where you are standing up a bit relative to true Earth.

So you can see voltages from around 1/2 supply (on long supply cable with R1 around R2) to close to the supply (if R2 is very high on TT system). But the danger of serious impact also depends on the exposure time, hence the values of 0.4s (typical LV TN-S) and 0.2s (TT) for max disconnection to try and keep the likely current-time exposure down.

If you are unfortnuate enough to be in good contact, say a swimming pool , then the current can be much higher even though a similar disconnection time is likely. Hence the requirement for SELV in that sort of high risk area as an RCD limits the exposure time, not the actual current, you might get.
So basically it’s the difference between the raised voltage of the installation when the fault occurs the the true earth we may be standing on that determines the voltage?
 

Reply to the thread, titled "Touch voltage to earth" which is posted in UK Electrical Forum on Electricians Forums.

Best EV Chargers by Electrical2Go! The official electric vehicle charger supplier.

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Advert

Daily, weekly or monthly email

Thread starter

Joined
Location
London
If you're a qualified, trainee, or retired electrician - Which country is it that your work will be / is / was aimed at?
United Kingdom
What type of forum member are you?
Other
If other, please explain
Maintenance Electrician

Thread Information

Title
Touch voltage to earth
Prefix
N/A
Forum
UK Electrical Forum
Start date
Last reply date
Replies
21
Unsolved
--

Advert

Thread statistics

Created
Jako13!,
Last reply from
LastManOnline,
Replies
21
Views
4,330

Advert

Back
Top