corner ground

[puckman]

i went on a service call today and came across a 3 phase 3wire 240v system that is from a transformer with a corner gound tap. this is the first time i've seen this. i'm told that one leg has 0v to ground and this leg should not be fused. is this a true fact ?
if anyone has any infomation about this type of a connection please post it here .
thanks for your help.

can someone tell me if the five 3 phase service fused disconnects at this plant are supposed to be fused in all 3 legs and if the grounded leg must be identifide? anyone have experience with this system?

 

[bcorbin]

This is true in all of the situations I've run into it. The corner is grounded intentionally. If the fuse were to somehow blow, that phase would no longer be correctly referenced to ground.

 

[don_resqcapt19]

The rules in Article 200 for the identification of grounded conductors apply to the grounded conductor of a corner grounded system. In general fuses are not permitted to be used in series with the grounded conductor. There is one exception for the case where fuses are being used as a motor overload protection.
Don

 

[JohnJ0906]

can someone tell me if the five 3 phase service fused disconnects at this plant are supposed to be fused in all 3 legs and if the grounded leg must be identifide? anyone have experience with this system?

I think a solid "fuse" is made for the grounded leg - just solid metal that will fit in the fuse holder.
The ones I have worked on used breakers, so I am not totally sure.