Open-wye Grounded Open Delta Connection

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cokei

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Hi! Can anyone help me on this? I have a problem in our area, we are supplying 1 customer and has a transformer banks connected in open-wye grounded primary open-delta secondary with center-tap grounded. During a line-to-ground fault in one phase of the primary line (where one phase of the open-wye transformer bank of the customer is connecdted), the cut-out fuse of that line got busted (open), at the same time that customer experienes a high voltage in their secondary side. In fact most of their appliances got burned. Can anyone has an idea why the open-delta secondary side of the transformer experienced high voltage? thanks
 
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cokei

Member
This a religious establishment particularly a church. Appliances that were damaged are 3-phase loads such as 5-tons aircon and single phase loads
includes TV, Desktop Computers,etc.
 
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cokei

Member
This is a commercial establishment. Appliances that were damaged includes 3-phase loads such as aircons and 1-phase loads includes TV and computers.
 
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cokei

Member
Bob

Is the characteristic of wye-delta same as open-wye neutral grounded primary open-delta secondary? As the result of our investigation, only loads of the one-phase experience a problem where there is an increase in brilliance of the lights and a fast rotation of electric fans that triggers the damage of the equipment.
 
bob

bob

Senior Member
Location
Alabama
cokei said:
Bob
As the result of our investigation, only loads of the one-phase experience a problem where there is an increase in brilliance of the lights and a fast rotation of electric fans that triggers the damage of the equipment.
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After looking at the wiring diagram of an open delta, it appears that you lost
the phase feeding the lightning transformer(LTr). If so, the LTr secondary coil is still connected to the secondary of the other transformer and has a current path thru one half of the LTr coil via the neutral. It seems that there could be as high as 265 volts on one half of the lighting panel. The motor damage was due to a single phase condition. Some of the phase currents may approach 200% of normal. I have never seen the appliances damage occur. Maybe someone else can make a suggestion.

sreeja
Since the transformer is grounded(connected to the neutral) the primary voltage will
remain at the normal phase to neutral value.
 
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