In this tutorial, you will be shown how to use several of EasyPower’s power flow analysis features. EasyPower uses the most robust and accurate algorithm ever developed: the Current Injection Method. The program also uses the latest in sparsity algorithm techniques to find the steady-state power flow conditions of an operating power system.
To run power flow analysis:
Figure 1: Power Flow Analysis
The Overloads button is selected by default. Equipment items that are overloaded are highlighted red. Since no equipment in Simple.dez is overloaded, nothing is highlighted.
Note: EasyPower also highlights items that are within 10% of overload. This overload threshold can be adjusted in the PF Options dialog box.
Figure 2: Power Flow With Losses Displayed
Figure 3: Power Flow With Percent Voltage Drops Displayed
After running power flow, the effect of one or more motors starting in your system can be analyzed. EasyPower computes the system impact of a starting motor at the time when the motor acts as a locked rotor.
Figure 4: Temporary Motor Data Dialog Box
Notice the buses turn red. Their bus voltages are below the “Bus Undervoltage Threshold.” (The “Bus Undervoltage Threshold” defaults to within 5% of unity. This can be adjusted in the Tools > Power Flow Options dialog box on the Control tab.) In both power flow and motor starting analysis, you can quickly spot voltage problems in large systems by looking for red buses.
Figure 5: Motor Starting Analysis
For fast contingency studying and what-if checking, you can run power flows after making temporary changes to the equipment data. All modifications made to equipment data while in the Power Flow focus are temporary. The changes do not affect verified data entered in Database Edit focus. Generators, utilities, transformers, motors, loads, capacitors, and shunts can all be temporarily edited.
Figure 6: Motor With 120% Scaling Factor
Notice that the 120% motor load shown in is greater than the 100% motor load shown. Changing the Scaling Factor of a motor lets you to test different loading scenarios without changing the actual motor specifications.
Note: You can quickly scale multiple motors and loads by clicking Change Scaling Factor from the ribbon. The changes are applied to the motors and loads on your one-line that are selected green. This provides a fast and easy way to check peak loading conditions, light loading conditions, future additions, and other factors prevalent to a power system.
Click PF Options in the ribbon and then select the One-line Output tab.
Observe the different one-line options available.
Figure 7: Power Flow Text Output Dialog Box
Tip: You can also double-click on the window icons created in the lower left corner.
This has been a brief overview of EasyPower’s power flow program. Features such as LTCs, generator voltage control, motor group modeling, and many others are also available. The EasyPowerUser Manual and the Help system cover these power flow features in greater depth.