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Chapter 21 Harmonic Analysis PSCAD

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Chapter 21 Harmonic Analysis PSCAD
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    Chapter 21 Harmonic Analysis Because of the wide and ever increasing applications of power electronic devices, such as variable speed drives, uninterruptible power supplies (UPS), static power converters, etc., power system voltage and current quality has been severely affected in some areas. In these areas components other than that of fundamental frequency can be found to exist in the distorted voltage and current waveforms. These components usually are the integer multipliers of the fundamental frequency, called harmonics. In addition to electronic devices, some other non-linear loads, or devices including saturated transformers, arc furnaces, fluorescent lights, and cycloconverters are also responsible for the deterioration in power system quality. Operation Technology, Inc. 21-1  ETAP PowerStation 4.0  Harmonic Analysis Introduction The presence of harmonics in a power system can give rise to a variety of problems including equipment overheating, reduced power factors, deteriorating performance of electrical equipment, the incorrect operation of protective relays, interference with communication devices, and in some cases, circuit resonance to cause electric apparatus dielectric failure and other types of severe damage. Even worse, harmonic currents generated in one area can penetrate into the power grid and propagate into other areas, resulting in voltage and current distortions for the entire system. This phenomenon has become a major concern for power quality due to the ever-increasing usage of electronic devices and equipment in power systems. Using computer simulation, the phenomena of power system harmonics can be modeled and analyzed. The PowerStation Harmonic Analysis program provides you with the best tool to accurately model various power system components and devices to include their frequency dependency, non-linearity, and other characteristics under the presence of harmonic sources. This program has two analytical methods, Harmonic Load Flow and Harmonic Frequency Scan, which are the most popular and powerful approaches for power system harmonic analysis. By using those two methods in combination, different harmonic indices are computed and compared with the industrial standard limitations, existing and  potential power quality problems, along with security problems associated with harmonics, can be easily revealed. Causes to those problems can be   identified and different mitigation and corrective schemes can  be tested and finally verified. Some of the main features of the PowerStation Harmonic Load Flow  Study are summarized below:   ã Common & Integrated Database ã Fully Inherited 3-D Data Structure, Including Infinite Presentations, Unlimited Configurations, & Multiple Data Revisions ã Looped, Radial, or Combined Systems ã Systems with Multiple Swing Buses ã Systems with Isolated Sub-Systems ã Systems with Zero Impedance Branches (Tie Circuit Breakers) ã Systems with De-Energized Buses & Branches ã Automatic Adjustment of Cable/Line Resistance According to Operating Temperatures ã Automatic Adjustment of Transformer Impedance According to Tolerance ã Automatic Adjustment of Current Limiting Reactor Impedance According to Tolerance ã Multiple Loading Categories ã Load Diversity Factors ã Complete Fundamental Load Flow Calculation ã Automatic LTC Settings for Fundamental Load Flow ã Modeling of Frequency Dependency of Rotary Machine Impedance ã Modeling of Non-linearity & Frequency Dependency of Cable/Line & Transformer Impedance ã Modeling of Frequency Dependency of Other Power System Components & Loads ã Effect of Transformer Phase Shifting to Harmonic Flow ã Effect of Machine & Transformer Winding Connections & Grounding Types to Harmonic Flow ã Harmonic Current Injection Method ã Positive, Negative, & Zero Sequence Harmonics ã Harmonic Order up to 73 rd   ã Harmonic Voltage Source ã Harmonic Current Source ã User-Expandable Harmonic Source Library ã User-Selected Harmonic Source Inclusion by Device Categories Operation Technology, Inc. 21-2  ETAP PowerStation 4.0  Harmonic Analysis Introduction ã Calculation of Various Harmonic Indices Based on IEEE Standards ã Total RMS Value (RMS) for Both Bus Voltages & Branch Currents ã Total Arithmetic Summation Value (ASUM) for Both Bus Voltages & Branch Currents ã Total Harmonic Distortions (THD) for Both Bus Voltages & Branch Currents ã Telephone Influence Factors (TIF) for Both Bus Voltages & Branch Currents ã I*T Product for Branch Currents ã Built-in Harmonic Filters in Different Types ã Automatic Filter Sizing Based on Different Criteria ã Check and Flag Filter Overloading ã Verifying Performance of Harmonic Filters ã Graphic One-Line Display of Study Results ã Slider Bar to Display Fundamental Load Flow, Total & Individual Harmonic Distortion ã Graphic Plots of Voltage & Current Waveform for Viewing & Printing ã Graphic Plots of Voltage & Current Spectrums for Viewing & Printing ã Text Report for Input Data, Fundamental Load Flow Results, Voltage & Current Harmonic Indices, Tabulated Voltage & Current Harmonic ã Crystal Reports   for Preformatted Reports ã Flag Violations of Bus Total & Individual Harmonic Distortion Limits Some of the main features of the PowerStation Harmonic Frequency Scan  Study are summarized  below:   ã Same System & Component Modeling Capabilities for Harmonic Load Flow & Fundamental Load Flow ã Modeling of Frequency Dependency of Rotary Machine Impedance ã Modeling of Non-linearity & Frequency Dependency of Cable/Line & Transformer Impedance ã Modeling of Frequency Dependency of Other Power System Components & Loads ã Transformer Phase Shifting ã Machine & Transformer Winding Connections & Grounding Types ã Built-in Harmonic Filters in Different Types ã Automatic Filter Sizing Based on Different Criteria ã User-Definable Frequency Scan Range & Step ã Graphic One-Line Display of Study Results ã Slider Bar to Display Bus Driving Point Impedance Magnitude & Phase Angle at Selected Frequencies ã Graphic Plots of Bus Driving Point Impedance in Ohms for Viewing & Printing ã Graphic Plots of Bus Driving Point Impedance Phase Angle for Viewing & Printing ã Text Report for Input Data, Fundamental Load Flow Results, Tabulated Bus Driving Point Impedance Magnitudes & Phase Angles   Operation Technology, Inc. 21-3  ETAP PowerStation 4.0  Harmonic Analysis Study Toolbar 21.1 Study Toolbar The Harmonic Analysis Study Toolbar will appear on the screen when you are in the Harmonic Analysis Study mode. This toolbar has eight function keys as shown below.   Run Harmonic Load Flow Run Frequency Scan Display Options Report Manager Harmonic Analysis Plots Halt Current Calculation Get On-Line Data Get Archived Data Run Harmonic Load Flow Select a study case from the Study Case Toolbar when you are in Harmonic Analysis Study mode. Click on the Run Harmonic Load Flow  button to perform a harmonic load flow study. A dialog box will appear for you to specify the output report name if the output file name is set to Prompt  in the Output Report list box. The harmonic load flow study results will appear on the one-line diagram and can be viewed in output report text and plot formats after the calculation completes. Run Frequency Scan After selecting a study case from the Study Case Toolbar, click on the Run - Frequency Scan  button to  perform a harmonic frequency scan study. A dialog box will pop up asking you the output file name if Prompt  is set in the Output Report list box. As in the harmonic load flow study, study results are displayed on the one-line diagram and can be viewed in output report text and plot formats after the calculation completes. Display Options Click on the Display Options  button to customize the one-line diagram annotation display options under the Harmonic Analysis Study mode. See Display Options for more information. Report Manager Click on the Report Manager  button to select a format and view harmonic analysis output report. Harmonic analysis reports are provided in two formats: ASCII text files and Crystal Reports  . Operation Technology, Inc. 21-4  ETAP PowerStation 4.0
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