Discuss Earth fault on a TN-S system in the Electrical Engineering Chat area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

I have no pictures, however it seems the cable is damaged along the way, not at the terminations. Sorry for misleading.

We are struggling here trying to understand the situation.

Your protection settings are not coordinated, but that sounds like the least of the problems.

I understand the equipment is directly off a transformer - but we don't know the size.

Quite often the fault current at this point is well in excess of the level most people are used to, at home my fault current is a little over 1kA, direct on a medium sized transformer it could be in excess of 20kA, certainly this is way more than the usual mcb can handle, but within the range of acbs and mccbs.

The design of cables and connections for this type of fault current is not what many people are used to, for example, the normal size cable for 40/50A could be 6 or 10mm2, but this size of cable would not withstand fault levels of this order, the only suitable protection would be fuses as they limit the current with a fairly small let-through enabling the cable to survive, with mccbs at this fault current, one has to size the cable to withstand the let-through which is considerably more for a mccb than a fuse.

You need to check your perspective fault current and see if the cables can withstand that.

Protection settings have little impact at high fault currents as the mccbs are in fault limit mode, and have a let-through fixed by type of mccb
 

Reply to Earth fault on a TN-S system in the Electrical Engineering Chat area at ElectriciansForums.net

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
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock