EasyPower^® Tutorial - Harmonics Analysis

In this tutorial, you will be shown how to use several of harmonics analysis features in EasyPower Spectrum™. Three features are covered in particular:

• The summation of all harmonics
• The current flow of individual harmonics
• The frequency scan

Harmonics Focus

To run harmonics analysis, you must be in the Harmonics focus.

1. Open the file Bigger.dez in your Samples directory. Click Maximize to fill your screen with the one-line.
2. Click Harm ( Harmonics) on the ribbon to open the Harmonics focus. A new ribbon appears with buttons that are used in the harmonics calculations.

Summation of Harmonics

Click Summation. Total harmonic distortion values are displayed on the one-line as shown in the figure below.

Figure 1: Harmonic Distortion Calculations

By default, Current Total Harmonic Distortion and Voltage Total Harmonic Distortion are selected. The vertical and horizontal numbers on the one-line indicate I _THD and the diagonal numbers on the buses indicate V _THD.

In the example above, the I _THD through the capacitor on BUS-2 is 10.692 amps. The V _THD on BUS-2 is 0.427%. (The current and voltage units can be modified in the Harmonics Options > One-line Output tab.)

Current Root-Sum-Squared and Voltage Root-Sum-Squared display I _RSS and V _RSS values on the one-line. These currents and voltages, which include fundamental and harmonics, are equivalent to I _RMSM and V _RMS. In the Harmonics focus, the fundamental voltage at each bus is assumed to be 1 per-unit. (This can be modified in Harmonics Options > Control.) The fundamental currents for each equipment item are assumed to be either the full load current rating of the equipment or the calculated current at 1 per-unit voltage.

Additional summation information is also available for one-line display:

• IT Product and kVT Product indicate interference that could occur on a nearby telephone circuit.
• Voltage Sum determines peak voltage for comparison with equipment (for example, capacitor) peak voltage capability.
• Losses indicates the sum of fundamental and harmonic losses on individual equipment.
• Transformer K-factor and Transformer Derating show derating values based on ANSI C57.110.
• Conductor Derating determines the maximum fundamental load that can be supplied to a conductor with harmonics present.

Frequency Scan

1. Double-click on BUS-2 on the one-line. A frequency scan similar to the one below is displayed. Drag the splitter bar to the right to view the values for each calculated harmonic.

   
   
   

   Figure 2: Frequency Scan

   This frequency scan, by default, is based on a 1.0 per-unit current injection on BUS-2. The scan displays the BUS-2 per-unit voltage with respect to the harmonic frequency of this injected current. This per-unit voltage can also be considered a per-unit impedance as long as the current injection remains 1.0 per-unit.

2. Double-click in the plot area to customize the frequency scan window. For example, double-clicking on the curve enables you to specify a different style, color, and weight for the curve. You can right-click in the plot window to view all the available plot format options.
3. Click the lower Close button on the top right of the window to close the plot window. This returns you to the one-line.

Summation Bar Chart

1. On the one-line, select a bus and/or branch on the one-line.
2. Click Summation Bar Chart on the Harmonics ribbon.

   This opens a bar chart that displays the different harmonics present in the buses (voltage) or branches (current).

   

   Figure 3: Harmonics Bar Chart Example

Harmonic Current Flow

There are two distinct methods for harmonic current flow solutions:

• The Single Source Current Flow
• The All Source Current Flow

Single Source Current Flow

1. If you are currently viewing a plot window, activate the one-line window.
2. Select BUS-2 (so that it turns green).
3. Click Single Pt ( Single Point Current Flow). Your one-line should display the values shown in figure below.

   The Single Source Current Flow displays currents and voltages throughout the system based on a single harmonic current injection at a bus. In the case above, 1.0 per-unit (or 481 amps) of 5 ^th harmonic current are injected into BUS-2. The resultant 5 ^th harmonic current (in amps) and voltage (in system per-unit) are displayed on the one-line. (The units and injection current can be modified in the Harmonics Options dialog.) This information is useful for determining how a particular harmonic current will flow and what equipment will be affected.

   

   Figure 4: Fifth Harmonic Current Flow Based on BUS-2 Injection

All Source Current Flow

1. Click Find-Select.
2. In the Find dialog box, select 2W Transformer and type TX-4 in ID Name of Item to Find.
3. Click OK.
4. Click All Source ( All Source Current Flow). Your one-line should look similar to the figure below.

   
   

   Figure 5: Fifth Harmonic Current Flow Based On All Source Injections

The motors under bus “SWG-12” represent an 18-pulse drive. Each motor injects a spectrum of harmonics. (The injected harmonic spectrum is specified in each Motor Data database dialog box. The EasyPower device library also contains typical harmonic spectra which can be imported.) The currents and voltages are based on all the fifth harmonic injections from the sources in the system. (This specified harmonic can be modified in the Harmonics Options dialog box.) Notice the fifth harmonic currents cancel on transformer “TX 12”due to phase cancellation. The All Source Current Flow feature determines flows in a network with all sources contributing.

Harmonics Text Reports

Harmonics Reports enables you to create harmonics text reports. When the report check boxes are selected, tabulated text report information is created during each harmonics Summation All or Current Flow operation. These text reports can be opened after they have been created by selecting the appropriate report from under the Window button.

Conclusion

This has been a brief overview of EasyPower’s harmonics program. Features such as IEEE 519 verification, filter modeling, zero sequence and triplen harmonics calculations, multiple Y-axes for plots, harmonics bar charts, power flow link, and others are also available. The EasyPower User Guide and the Help system cover these harmonic features in greater depth.