Transformer Tap settings

[Sunshine97]

Can someone please tell me if there is any actual use case with a -2.5% and -5% Tap settings for a MV Transformer. My understanding is+2.5% and +5% will help in reducing the current and thereby the losses.

Thanks in advance.

 

[jim dungar]

Can someone please tell me if there is any actual use case with a -2.5% and -5% Tap settings for a MV Transformer. My understanding is+2.5% and +5% will help in reducing the current and thereby the losses.

Thanks in advance.

You would be correct, but that is not what taps are typically used for.

The tap is intended to compensate for the corresponding difference in the nominal versus actual supply voltage. Utilities are much more likely to experience a below nominal voltage so transformer usually have -% taps.

 

[Sunshine97]

@jim dungar Thank you very much for your response.

I am kinda lost here. How do I figure out what tap settings to use for a transformer? We have a 34.5 KV utility line and we have a system interconnected to it with a 34.5 KV Pad mount transformer feeding the grid. So, no need to adjust the tap settings here and set it at 0%?

But what happens if I set it at +2.5% or -2.5%?

Thank you!

 

[LarryFine]

Welcome to the forum.

What changing the taps actually does is apply the incoming voltage to a different quantity of primary windings, which alters the volts-per-turn ratio, which in turn adjusts the secondary output voltage.

This will affect the load current to whatever degree altering the voltage to the load would normally would.

 

[GoldDigger]

@jim dungar Thank you very much for your response.

I am kinda lost here. How do I figure out what tap settings to use for a transformer? We have a 34.5 KV utility line and we have a system interconnected to it with a 34.5 KV Pad mount transformer feeding the grid. So, no need to adjust the tap settings here and set it at 0%?

But what happens if I set it at +2.5% or -2.5%?

Thank you!

Your profile lists you as a Performance Engineer, not necessarily an electrical professional. As such your general question about transformer taps falls within allowed Forum posts. Giving you advice about making an electrical decision that should be made by an electrical professional falls outside that limit.
As has been stated already, transformer taps can be used both to correct for variations of the actual input voltage from the nominal voltage and potentially to correct for a large voltage drop in the output circuit. That decision about tap selection is not an arbitrary action.

 

[electrofelon]

PV systems are a common case where taps can come in very handy.

 

[GoldDigger]

PV systems are a common case where taps can come in very handy.

In particular where the voltage rise resulting from resistance can drive the voltage at the inverter terminals outside the allowed range for the inverter.