Transformer Display

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The Transformer Display identifies all transformers in the case. The data presented in the Transformer Display supplements the data presented in the Line/Transformer Display by presenting transformer-specific information. Consult the Line/Transformer Display for the transformer flows.

The Transformer Display is a class of Case Information Display and therefore can be used in a manner consistent with all other case information displays. It has a local menu from which you can print, copy, and modify its information as well as view the information dialog of its associated transformer. You can find a specific transformer using the names or numbers of its terminal buses, and you can learn more about a particular transformer’s terminal buses by choosing either Quick Power Flow List or Bus View. When in Edit Mode, you can delete an existing transformer from the case. You can also sort the transformer information by clicking on the heading of the field by which you want to sort.

To show this display select Network > Transformers Controls in the Model Explorer.

 

The Transformer Display contains the following fields by default:

From Bus Number and Name

From Bus number and name. The From Bus is the tapped side. You may view either the Quick Power Flow List or the bus view display for the From Bus from the local menu.

To Bus Number and Name

To Bus number and name. You may view either the Quick Power Flow List or the bus view display for the To Bus from the local menu.

Circuit

Two-character identifier used to distinguish between multiple transformers joining the same two buses.

Status

The service status of the transformer. This field is toggleable.

Type

Type of transformer. Possible values include

Fixed  The tap positions are fixed

LTC  The tap ratio changes to regulate bus voltage

Mvar The tap ratio changes to regulate reactive power flow

Phase  The phase angle changes to regulate real power flow

Tap/Phase

Indicates the tap ratio for LTC and fixed transformers and the phase shift angle in degrees for phase-shifting transformers.

XF Auto

If the value of this field is Yes, the transformer will automatically change its tap or phase angle to keep the regulated value within the specified regulation range, provided that the Auto XF field of its associated area is set to Yes and transformer tap/phase control has not been disabled for the entire case. The Auto XF field of individual areas is set from the Area Display, and case-wide transformer control can be set from the Power Flow Solution tab of the Simulator Options Dialog. Click on this field to toggle its values.

Reg Bus

For an LTC transformer, this is the number of the bus whose voltage is controlled by the transformer. For phase shifting transformers, the real power is always controlled at the tapped bus.

Reg Value

For an LTC transformer, this is the present per unit voltage at the regulation bus. For a phase shifting transformer, this is the present real power flow through the transformer measured on the "from" (tapped) side.

Reg Error

The error is the difference between the regulated value and the respective limit of the regulation range specified by Reg Min and Reg Max. If the regulated value is within the regulation range, then the error is zero. The error is negative if the regulated value falls below the regulation range, and it is positive if the regulated value exceeds the regulation range.

Reg Min, Reg Max

Minimum and maximum values for the regulation range. For LTC transformers, these fields represent per unit voltage at the regulated bus. For phase shifting transformers, these fields represent actual MW flow through the transformer measured on the "from" (tapped) side. Because transformers use discrete control, the maximum regulation value must be somewhat greater than the minimum value.

Tap Min, Tap Max

For LTC transformers, these fields specify the minimum and maximum tap ranges for the transformer. For phase shifting transformers, these fields specify the minimum and maximum phase shift angle in degrees.

Step Size

The per unit step size for tap changing transformers. This step size is usually determined by dividing the total range of transformer operation by the number of tap positions available.