TN Undergo the fault ... but cause tripping to provide protection
This fault is similar to a short-circuit and thus violent and destructive. The circuit-breaker in this case trips on the 1st fault.
No needs of RCD and PIM. TN System is less cost the TT and IT but it becomes very quickly costly in the case of modifications or extensions. Moreover, it is hard on installations due to short-circuit effects on cables and loads, plus the fact that voltage drops can disturb computers, etc.
To limit the consequences of the fault to the part of the network concerned, overcurrent, time and energy discrimination methods must be implemented.
Another possibility is offered with the implementation of the TNS directly downstream from the transformer, which has the advantage of tripping via the RCD due to detection before the short-circuit.
