[0] Advantages [IT] Continuity of operation, cost [TN-S] Safest [TN-C] Cost [TN-C-S] Safety and cost [TT] 
Safe and reliable
H i g h
Y e s
L o w
N o
S a f e
L e a s t
H i g h l o o p i m p e d a n c e ( s t e p v o l t a g e s )
S a f e a n d r e l i a b l e