Inrush Current in HV winding ? Input 380V at 11kV/380V Tx HV side

[h0001244]

My boss asked me to distinguish Dy11 and Dy1 in very low cost.
Tx: 11kV / 380V Dy11 1.5MVA transformer

My suggestion is that simply input 380V 3phase domestic supply into HV side of 11kV/380V, then we can get around 13V at LV side. Connect the supply neutral to LV neutral. Now we have VA,VB,VC on HV side and Va,Vb,Vc on LV side.

If it is Dy0, Va-VB should be equal to Va-VC, right?
If it is Dy11 or Dy1, Va-VB should be different from Va-VC, then we can identify between Dy1 and Dy11.

But my question is that I haven't considered the inrush current on the HV side when I apply 380V 3phase to it. Any suggestions or comment?

 

[Kiribanda]

h10001244,
Connection symbol test is a routine test.Therefore,there is a standard test method to check the connection symbol.Per the ratio (11 kV-380V) it looks to me your transformer "belongs" to the IEC world.But as far as I can remember IEC60076 does not specify how to do the connection symbol test for Dyn11 IEC transformers.TRANSFORMER HANDBOOK has given how to do that for variuos connection symbols.Also IEEE C57.12.90 specifies how to check the connection symbol for Dyn1 ANSI transformers.I donot think other "cheap" test methods will give you an accurate picture for a decision.

 

[h0001244]

Thanks Kiribanda.......

Is IEC world having a big difference? In fact I am very young and have no idea on the difference of the standard. Can you tell me more?
Could we just treat it as electrical apparatus in this case? I measured difference between Va-VB and Va-VC, but when I think of the inrush current, I have no idea on it especially the HV winding.

 

[rcw retired EE]

Inrush current will be approximately less by the 380V/11kV ratio. Calculate the 11 kV full load current, ratio it down for your 380V applied voltage and then assume inrush will be the "rule of thumb" 10-12 times that value.

 

[Kiribanda]

h0001244,

Can you tell me more?
Sorry. This forum is not a platform for teaching.Your boss has a duty to guide you.

Could we just treat it as electrical apparatus in this case?
I donot understand the above statement.

 

[pie314]

I agree with rcwilson except his multiplier of "10 - 12 times". This amount of inrush only occurs if the core saturates. Since the applied voltage is well below rated, the core will not saturate. If the transformer is energized @ a voltage zero, then the multiplier will be a factor of 2 not "10 to 12"

 

[Paszt]

"Sorry. This forum is not a platform for teaching.Your boss has a duty to guide you." - Strange, I actually thought this WAS a platform for teaching and sharing knowledge. Am I at the wrong place?

 

[h0001244]

Thanks all...
What makes the difference when core is not saturated? I mean, does it mean that the inrush current would be smaller when core is not saturated?

 

[rcw retired EE]

Good point on saturation, Pie. I figured the resulting calculated inrush would be worst case but that it would still be so small to not be problem for a typical service.

 

[Masbibe]

h0001244,

I didnt undestood what is your task.

Possible Dy transformers are Dy1,Dy3,Dy5,Dy7,Dy9,Dy11 (not Dy0 as you said).

In all cases voltages UaB and UaC are differents.


Milovan Milosevic