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Anonymous Poster

# How Does a Zig-Zag Transformer Sense the Earth Fault?

05/01/2008 2:17 PM

Why a zig zag transformer is used?

Answer: To provide an artificial neutral point for delta side of transformer

My argument is an artificial neutral point can also be provided with a star connected transformer.So why a special earthing/zig zag transformer?

I heard that zig zag transformer provides a low impedance path to zero sequence currents as the windings per phase are split and oppose each others magnetic flux.

In simple words how zig zag transformer senses the earth fault?kindly explain

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Power-User

Join Date: Sep 2006
Posts: 367
#1

### Re: Why a zig zag transformer is used?

05/01/2008 3:40 PM

Transformers have Zig-zag three phase connections suppling voltages to unbalance loads. Uneven currents on the x-fer secondary are somehow become balanced from the primary windings point of view. And it does not matter if primary is Delta or Star(Wye). The zig-zag windings (two per phase *three phases) are placed on three Fe cores of transformers to create as close as possible to balances 3-ph magnetic field, which is "the carrier" for electromagnetic power.

So D or Y / Zig-zag are used in unbalanced low voltage system - mostly with single phase appliances.

Anonymous Poster
#2

### Re: How Does a Zig-Zag Transformer Sense the Earth Fault?

01/19/2009 2:09 PM

a zigzag transformer is more effective for grounding purposes because it has less internal winding impedance going to the ground than when using a wye-type transformer.

Anonymous Poster
#3

### Re: How Does a Zig-Zag Transformer Sense the Earth Fault?

07/29/2010 7:50 AM

yes artifical neutral point can be provided with star connected transformer but when u compare the cost star transformer is expensive.

It provide the low impedance path it is true.........

But along with the zigzag transformer neutral grounding resistor is connected which limits the earth fault current to the desired value.

depending upon the resistor selected earth fault current can be limited 100,200........etc amps

This limited earth fault current is sensed by the earth fault relays connected in the sytem