Two-Winding Transformer Data Type

The Two-Winding Transformer represents the device in a Substation that either steps up or steps down the voltage between two nodes. There are a few key modeling considerations that should be noted for the Transformer data type. First, the transformer ratio is dictated by the ratio of the base KV of its FromNode and ToNode. It is not set directly as a property of the Transformer. Therefore, a Transformer can exist as simply a series impedance connection between two nodes with no transformation of voltage if the base KV of its FromNode and ToNode are set to the same value. Additionally, there is no convention for which side of the Transformer is considered the high side or the low side. Again, the base KV of the FromNode and ToNode of the Transformer dictates this. Second, the type of Transformer (either Delta-Wye, Wye-Wye, Wye-Delta, or Delta-Delta) is dictated by two properties. The FromNodeConnectionType and ToNodeConnectionType specify whether a node exists as a Delta connection or as a Wye connection. Specified individually, these two properties give the ability to model a Transformer with any configuration of connections to be modeled. Third, the Transformer can only be a child of a Substation object. Fourth, its tap model drives the behavior of the Transformer’s tap. This is specified by the TapConfigurationID property. This is the integer identifier of the TapConfiguration that models the behavior of the Transformer tap. The Transformer does have the ability to accept telemetry indicating the prevailing position of the tap. The signal is indicated with the TapPositionInputKey property. The prevailing position of the tap can also be translated into an output signal by specifying the TapPositionOutputKey property. Fifth, in order for the Transformer to accept the signal dictated by the TapPositionInputKey property, the property UltcIsEnabled must be set to true. Otherwise, the tap position will default to the value indicated by the FixedTapPosition property. Finally, the tap of the Transformer is assumed to be connected to the from side of the Transformer. This is critical for assigning the FromNodeID and ToNodeID of the Transformer since the tap makes the two-terminal device asymmetrical in its matrix representation. These properties are outlined in the following table:

Transformer Property/Attribute Table
Property Name Xml Name Type Description
UniqueId Uid Guid A statistically unique identifier for the instance of the Transformer data type. Lazily instantiated.
InternalID ID Integer A non-zero, positive, integer, unique identifier for the instance of the Transformer data type.
Number Number Integer A non-zero, positive integer non-unique descriptor for the instance of the Transformer data type.
Name Name String A non-unique name descriptor for the instance of the Transformer data type.
Description Description String A non-unique description for the instance of the Transformer data type.
FromNodeID FromNode Integer The InternalID of the Node object which is electrically connected to the From side of the Transformer. A Transformer is not symmetrical in that it assumes the tap box is located on the From side of the Transformer.
ToNodeID ToNode Integer The InternalID of the Node object which is electrically connected to the To side of the Transformer.
FromNode-ConnectionType FromNode-ConnectionType Transformer-ConnectionType Either Delta or Wye. Results in an appropriate 30 degree phase shift.
ToNode-ConnectionType ToNode-ConnectionType Transformer-ConnectionType Either Delta or Wye. Results in an appropriate 30 degree phase shift.
FromNodeCurrent-PhasorGroupID FromNodeCurrent-PhasorGroup Integer The InternalID of the CurrentFlowPhasorGroup which has measurements originating at the From side of the Transformer.
ToNodeCurrent-PhasorGroupID ToNodeCurrent-PhasorGroup Integer The InternalID of the Current FlowPhasorGroup which has measurements originating at the To side of the Transformer.
ParentSubstationID ParentSubstation Integer asdf
TapConfigurationID TapConfiguration Integer The InternalID of the TapConfiguration of the Transformer. See TapConfiguration Data Type Section.
TapPositionInputKey TapPositionInputKey String A string key used to uniquely identify the input measurement which contains the measured state of the Transformer Tap Position.
TapPositionOutputKey TapPositionOutputKey String A string key used to uniquely identify the output measurement and map the prevailing value of the Transformer Tap.
FixedTapPosition FixedTapPosition Integer The desired tap position for the Transformer tap when not in ULTC mode.
UltcIsEnabled EnableUltc Boolean A flag which determines whether the Transformer is in ULTC mode or not. When in ULTC mode, the Transformer will accept input measurements for determining the prevailing tap position. Otherwise, the Transformer will assume the FixedTapPosition.
RawImpedanceParameters Impedance Impedance The Impedance of the Transformer. See Impedance Data Type Section.
FromNodeCurrent FromNodeCurrent CurrentFlow-PhasorGroup The CurrentFlowPhasorGroup with measurements originating at the From side of the Transformer.
ToNodeCurrent ToNodeCurrent CurrentFlow-PhasorGroup The CurrentFlowPhasorGroup with measurements originating at the To side of the Transformer.


<Transformer Uid="286f8570-f20d-4b2e-aa23-94bc040cdf6a" ID="1" Number="1" Name="SubstationA TX 1" Description="SubstationA TX 1 Description" FromNode="10" ToNode="9" FromNodeConnectionType="Wye" ToNodeConnectionType="Wye" FromNodeCurrentPhasorGroup="10" ToNodeCurrentPhasorGroup="11" ParentSubstation="1" TapConfiguration="1" TapPositionInputKey="Undefined" TapPositionMeasurement="0" TapPositionOutputKey="Undefined" FixedTapPosition="0" EnableUltc="false">
	<Impedance />
	<FromNodeCurrent />
	<ToNodeCurrent />
</Transformer>

Last edited Sep 16, 2014 at 1:17 AM by kevinjones, version 1