Short Circuit Analysis Using ETAP | IEC 60909
Short circuit analysis using ETAP software based on IEC 60909 standard.
In the previous discussion, we have presented the step-by-step process of short-circuit calculation based on IEC 60909. The calculations were quite intensive and time-consuming as compared to ANSI-approved methods thus the use of computer software is recommended. As with our final discussion on ANSI short-circuit calculation method, we will conclude the IEC 60909 series with a short circuit analysis using ETAP software.
Before proceeding to the topic, it is recommended that you familiarize yourself with the software user interface. You can refer to this link to review the basic elements and toolbars available in the software, and the step-by-step process of modeling. We will be using the same network as with the ANSI short-circuit application example so that we can make a comparison of the results.
At this point, you are expected to know already how to model the sample network in ETAP. Your network model should look like the figure as shown below.
Verify that the following device parameters are consistent with your model. These parameters are pre-requisite to running the short circuit analysis using ETAP for IEC 60909.
Utility
Rated kV: 25
3-Phase MVAsc: 228.964
3-Phase kAsc: 5.288
X/R: 17.887
Transmission Line
R – T1 Pos.: 0.08171 (Unit in Ohms)
X – T1 Pos.: 0.18041 (Unit in Ohms)
Synchronous Generator
kV: 25
MVA: 5.952
FLA: 137.5
Xd”: 19
Xd”/Ra: 19
Xd: 155
Exciter Type: Turbine 130%
Setting-up the Study Parameters
After reviewing the device parameters, we are now ready to set-up the study case. Navigate to the Study-Case toolbar and click the ‘Edit Study Case’ button. Verify that the faulted bus is Bus2.
Navigate to the ‘Standard’ tab. Select ‘IEC’ for the ‘Standard’ field and ‘Max.’ for the ‘Short-Circuit Current’ field. Leave all other fields to their default values.
Next, navigate to the ‘Adjustment’ tab and uncheck all checkboxes as shown in the figure below.
Notice that the ‘Resistance Temperature Correction’ fields are greyed-out. Remember that IEC 60909 requires the resistance correction of a transmission line to 20°C for the calculation of maximum short-circuit currents. You can review the resistance correction calculation through this link.
You can now close the ‘Study Case’ window by clicking ‘OK’. After setting-up the study case, the short-circuit toolbar on the right side of your ETAP window should look like the figure below.
Before running the Short circuit analysis using ETAP, it is important to identify what equipment is to be specified. In this example, we are interested in the circuit breaker. Double-click on the high-voltage circuit breaker on the one-line diagram and navigate to the ‘Rating’ tab and click on the ‘Library’. A new window should pop-out. Select the circuit breaker as shown and click ‘OK’.
On the ‘Min. Delay’ field drop-down list, select 0.05. This is to be consistent with our calculation using the ANSI-approved method where we set the rated interrupting time to 3 cycles. Click ‘OK’ to close the high-voltage circuit breaker editor.
Short-Circuit Analysis
To start the short circuit analysis using ETAP, click on the ‘Run 3-Phase Device Duty (IEC 60909). If a new window will pop-out requiring you to specify the report name. Enter the output file name of the report and click ‘OK’.
Click on the ‘Report Manager’ in order to open/view the study output report. For this example, click on the ‘Summary’ tab and select ‘Summary’. Click ‘OK’.
Comparison of Results
The following table shows the short-circuit analysis results for the same network using the ANSI-approved method and the IEC 60909.
Final Thoughts
Short-circuit analysis is a very important process in the planning and design of any power system. There are different international standards that address the method of calculation but among these, the most common is the ANSI-approved standards and the IEC 60909 standard. These standards have different approach in the calculation of short-circuit currents and device duties with IEC 60909 more computationally intensive and conservative. The choice regarding which standard to use depends on the design engineer but more importantly should be based on the standard to which the equipment to be acquired or assessed is certified.
References
ETAP Enterprise Solution for Electrical Power Systems Online Help
