Neutral Grounding

this is real stupid query???

The zig-zag connection is a very good solution, but preferably with a neutral reactance connected. this is the so far known Resonant Grounding, useful when the purpose is to limit the phase to ground fault current. But in this solution you must have means to control the neutral reactance in order to always provide a ressonance between the reactance and the system associated capacitance. Please refer to Trench web-site.

Cheaper would be to ground the system by means of a resistor providing a high current phase to ground fault. But you have to check the conditions to keep the system grounded, if required by using the ratio Ro/Xo< = 3

Those who don't deserve to give a reply or through light should not passon bad remarks.

el..I appreciate your reply and effort.

But I have an answer.

1. for any old system restricting ground fault current to 300A is not desirable, since you don't know how much GF current old equipments can withstand.

2. Going for 10A , in case of Zig-Zag transformer, the resistance valus becomes more and thereby cost is higher.

3. Star-open delta with secondary resistance and zero sequence voltage relay, costs less since reflected resistance value is much less than former one. Now a days high sensitive zero sequence voltage relay considering microprocessor based relay also costs less. Thus alternatively cost wise second option is better.

There is IEEE publication which supports my answer.

Any one can put more light is welcome.

Mr Guest hope you should go to graduate school again before puting such coments in this forum.