Power System Blockset    

Setting the Initial Load Flow and Obtaining Steady-State

Before performing transient tests on your case1 system you must initialize your system for the desired load flow. Use the load flow utility of the powergui to obtain an active power flow of 1500 MW out of the machine with a terminal voltage of 1 p.u. (13.8 kV).

Open the powergui. In the Tools menu, select Load Flow and Machine Initialization. A new window appears. In the upper right window you have a the name of the only machine appearing in your system: 6*350*MVA 13.8 kV. Its Bus Type should be PV Generator and the desired Terminal Voltage should be already set to the default value (nominal voltage of 13800 V). In the Active Power field, enter 1500e6 (1500 MW) as the desired output power. Click on the Execute Load Flow button. Once the load flow is solved, the phasors of AB and BC machine voltages as well as currents flowing in phases A and B are updated in the left window. The required mechanical power to drive the machine is displayed in watts and in p.u. and the required excitation voltage E is displayed in pu:

Notice that constant blocks containing these two values are already connected to the Pm and E inputs of the machine block. If you open the machine dialog box, you will see that the machine initial conditions (initial speed deviation dw=0; internal angle theta, current magnitudes and phase angles) have been automatically transferred in the last line.

Once the load flow is performed, you can obtain the corresponding voltage and current measurements at the different buses. In the Tools menu, select Steady State Voltages and Currents. You can observe, for example, the phasors for phase A voltages at buses B1, B2 and B3 and the current entering line 1 at bus B1.

The active power flow for phase A entering line 1 is therefore

corresponding to a total of 464*3=1392 MW for the three phases.


 Description of the Transmission Network Transient Performance for a Line Fault