Page Comparison

Winding 1 connection (Gride-side)

The winding connectors for winding 1 on the gride side. Choices are Y, Yn, Yg (default), Delta (D1), and Delta (D3). Default is Yg.

Winding 2 connection (Converter-side)

The winding connectors for winding 1 on the Converter side. Choices are Y, Yn, Yg (default), Delta (D1), and Delta (D3). Default is Delta (D1).

Type

Select Three single-phase transformers (default) to implement a three-phase transformer using three single-phase transformer models. You can use this core type to represent very large power transformers found in utility grids (hundreds of MW).

Select Three-limb core (core-type) to implement a three-limb core three-phase transformer. In most applications, three-phase transformers use a three-limb core (core-type transformer). This type of core produces accurate results during an asymmetrical fault for both linear and nonlinear models (including saturation). During asymmetrical voltage conditions, the zero-sequence flux of a core-type transformer returns outside the core, through an air gap, structural steel, and a tank. Thus, the natural zero-sequence inductance L0 (without delta winding) of such a core-type transformer is usually very low (typically 0.5 pu < L0 < 2 pu) compared with a three-phase transformer using three single-phase units (L0 > 100 pu). This low L0 value affects voltages, currents, and flux unbalances during linear and saturated operation.

Select Five-limb core (shell-type) to implement a five-limb core three-phase transformer. On rare occasions, very large transformers are built with a five-leg core (three phase legs and two external legs). This core configuration, also known as shell type, is chosen mainly to reduce the height of the transformer and make transportation easier. During unbalanced voltage conditions, as opposed to the three-limb transformer, the zero-sequence flux of the five-limb transformer stays inside the steel core and returns through the two external limbs. The natural zero-sequence inductance (without delta) is therefore very high (L0 > 100 pu). Except for small current unbalances due to core asymmetry, the behavior of the five-limb shell-type transformer is similar to that of a three-phase transformer built with three single-phase units.

Units

Specify the units used to enter the parameters of this block. Select pu to use per unit. Select SI to use SI units. Changing the Units parameter from pu to SI, or from SI to pu, automatically converts the parameters displayed in the mask of the block. The per unit conversion is based on the transformer rated power Pn in VA, nominal frequency fn in Hz, and nominal voltage Vn, in Vrms, of the windings. Default is pu.

Nominal power Pn

VA

The nominal power rating , in volt-amperes (VA), of the transformer. The nominal parameters have no impact on the transformer model when the Units parameter is set to SI. Typically, its value is 1.2 times the Nominal Power Pn (VA) of the controller indicated in the controller Tab. Default is 72000.

Winding 1 (Grid-side) parameters

The phase-to-phase nominal voltage in volts RMS, resistance, and leakage inductance in pu for winding 1. Default is [ 6600 , 0.004 , 0.04 ] when the Units parameter is pu and [7.35e+05 4.3218 0.45856] when the Units parameter is SI.

Winding 2 (Converter-side) parameters

The phase-to-phase nominal voltage in volts RMS, resistance, and leakage inductance in pu for winding 2. Default is [480, 0.004 , 0.04 ] when the Units parameter is pu and [3.15e+05 0.7938 0.084225] when the Units parameter is SI.

Magnetization resistance Rm

The magnetization resistance Rm in pu or SI depends on the Units parameter. Default is 500 when the Units parameter is pu and 1.0805e+06 when the Units parameter is SI.

Magnetization inductance Lm

The magnetization inductance Lm, in pu, for a nonsaturable core. Default is 500 when the Units parameter is pu and 2866 when the Units parameter is SI.

Inductance L0 of zero-sequence flux path return

The Inductance L0 of zero-sequence flux path return, in pu, for the three-limb core transformer type. This parameter is visible only if the Type parameter is set to Three-limb core (core type). Default is 0.5 when the Units parameter is pu and 2.866 when the Units parameter is SI.

Inductance L0 of zero-sequence flux path return

The Inductance L0 of zero-sequence flux path return, in pu, for the three-limb core transformer type. This parameter is visible only if the Type parameter is set to Three-limb core (core type). Default is 0.5 when the Units parameter is pu and 2.866 when the Units parameter is SI.