Trafo (Transformer)

Double-clicking on a transformer component should pop up the properties window. Information includes: operating, economic and graphical (and locational) information.

Figure 25. Operational Information in the Transformer Properties window

User can define the following information in the Transformer’s properties window:

• Nominal voltage P: Nominal voltage of the primary in kV

• Nominal voltage S: Nominal voltage of the secondary in kV

• Pcu: Losses due to winding resistance in kW

• Pfe: Losses in the transformer’s core in kW

• Uk: own-base series impedance

• I0: own-base magnetization Impedance

• Smax: Maximum Transformer’s capacity in MVA

• Sn: Rated power in MVA

The values of pcu, uk, and I0 can be calculated by the DeepEdit when user enters the parameters of the resistance and the reactance in p.u. of the PI model of the transformer. These parameters can be entered in the Operation Information section (Parameters in (p.u.)) as shown in the figure.

Figure 26. Parameters in pu in the Transformer Properties window

The values of pcu, uk, and I0 will only be calculated if the parameter ur1 is equal to the nominal voltage of the primary and ur2 is equal to the nominal voltage of the secondary, and if only the model has capacitive components in parallel. The calculations made by the DeepEdit using the π-model are as follows:

• Sn: Nominal Power of Trasformer [MVA] 0≤Sn≤Smax

• Sref: System reference Power [MVA] (typically 100). System reference power can be entered by selecting the Schematic options in the Analysis Tools menu.

• X: π-model reactance in pu.

• R: π- model resistance in pu.

NOTE: The values of Sn must be entered for the calculation of pcu and uk, and they both need to be greater than 0 and less than or equal to Smax. This will be alerted by the properties window, preventing it from closing if conditions are not met.

Figure 27. Economic Information in the Transformer Properties window

The economic information is as follows:

• Life Time: Years in which the transformer depreciates

• Entry Year

• Entry Month

• Exit Year

• Exit Month

• Investment cost Investment cost of the Transformer (VNR) in UD Dollars

• COYM Cost of operation and annual maintenance of the Transformer in dollars

In the graphic information section of the transformer, Users can modify the orientation (horizontal or vertical) in which DeepEdit shows the transformer.

Figure 28. Graphic Information in the Transformer Properties window

The four possible drawing positions of Transformers are:

~ Trafo Graphic

~ Trafo Graphic V

~ Trafo Graphic S

~ Trafo Graphic VS

Figure 29. Display positions of transformers

Transformer parameters calculation

Assume that the following values are defined for a transformer:

• Uk = 11.5266% short-circuit test voltage as a percentage of the nominal voltage according to the manufacturer,

• Pcu = 292.5 kW copper losses associated with the short circuit test,

• I0 = 2% No-load current test as a percentage of the rated current,

• Sn = 75 MVA Nominal apparent power of the transformer,

• Ur1 = 220 kV Nominal voltage according to manufacturer on the primary side,

• Ur2 = 110 kV Nominal voltage according to manufacturer on the secondary side,

• Un1 = 220 kV Nominal voltage of the system on the primary side,

• Un2 = 110 kV Nominal voltage of the system on the secondary side,

• Sb = 100 MVA Base power of the system.

Thus, the values in per unit (on a common basis) will be given by:

For the parameters given above:

• rcc = 0.0052 pu

• Zcc = 0,1537 pu

• xcc = 0,1536 pu

• bm = 0.01 pu