Impedance grounding

When the neutral i.s impedance grounded, three times its impedance must be added to Zp. in view that this impedance would fall in series with each phase. 

An impedance grounded system will fall into this category. The GFF may now exceed 1.4 (K > O.SV f). 

The above problem can also be overcome by impedance grounding rather than solid grounding. It can be a resistance R or inductance L or both, as discussed above. In the present case, if we consider a p.u. resistance / of Just 9% in every neutral, the improved ground fault current... 

A scheme for a ground fault protection will depend upon the type of system and its grounding conditions, i.e. whether the system is three-phase three-wire or three-phase four-wire. A three-wire system will require an artificial grounding while for a four-wire system the type of grounding must be known, i.e. whether it is effectively (solidly) grounded or non-effeclively (impedance) grounded. 

FIGURE 5.3 Low-impedance ground reference, provided by the earth, between several buildings in the same facility. 

Figure 27.7 Illustration of the Importance of a low impedance grounding conductor...

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