Transformer Tap settings

[mikeengurs]

Electrical system study with all loads connected showed we need to modify primary Taps to -5% to maintain voltage. Currently, most of the loads are not connected, and bus voltages at MV level is around 4300v. If Taps are changed now, voltages might get over 4500v, which is high. First, would a higher voltage like that hurt loads? What is the best approach when it comes to changing transformer Taps? Should we do that now, or add loads slowly and see what that does?

 

[prc]

From the post,it is assumed that taps are on HV for HV variation.So for constant primary voltage if you change to minus tap,transformer will be overfluxed to that extent with higher secondray voltage.If the tap changer is of on-load type,tap changing need to be done only when secondary voltage dips.Whether overvoltage hurts the loads- it depends on the type of load.

 

[mikeengurs]

Thanks for the reply. I guuess what I was trying to ask is, what is usually the bus voltage range recommended by standards?

 

[ScottyUK]

In the UK the declared range is +/- 6% on nominal for a public utility supply. You'll have to check the equivalent regulations for yuor location.


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If we learn from our mistakes I'm getting a great education!

 

[prc]

Permissible voltage ranges are given nin standards. eg ANSIC84.1-2006, IEC 60038-2009
For Nominal voltage of 4160 V, the permissible range is 4370-4050 Volts as per ANSI

 

[mikeengurs]

Thank you guys...that was helpful!

 

[DTR2011]

It is advisable to perform a turns ratio test after changing taps.