adv trans stability

Version 5.20.00 November 2008

Advanced Transient Stability Analysis

Power Analytics Corporation 10805 Rancho Bernardo Road, Suite 270

San Diego, California 92127 U.S.A.

U.S. Toll Free Phone: 800-362-0603 Fax: 858-675-9724

www.PowerAnalytics.com

Copyright Power Analytics Corporation 2012 All rights reserved


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Table of Contents Page

Important Product Function Announcement ................................................................................................. 1

Security Index Calculation in the Advanced Transient Stability Program .................................................... 1

Advanced Transient Stability Capabilities, Features and Functions ............................................................. 2

Introduction to Advanced Transient Stability ................................................................................................. 4

Supported Events (Disturbances) ............................................................................................................. 5 Required Steps to Run Transient Stability Program ................................................................................. 6 What to Do When the Simulation Terminates Abnormally: ....................................................................... 7 Data Entry .................................................................................................................................................. 7

Entering the Generator Data ................................................................................................................ 10 Summary of Generator Types and Data Requirements ...................................................................... 14 Utility Model in the Transient Stability .................................................................................................. 16 Induction Machine and Data Requirements in the Transient Stability Analysis .................................. 16

Simulating Events (Disturbances) ............................................................................................................... 21

Changing Mechanical Torque of an Induction Machine .......................................................................... 23

Relay Models In Transient Stability ............................................................................................................. 24

How to Model Over Current Relay in Transient Stability Analysis .......................................................... 29

How to Model Breakers in Transient Stability Analysis ............................................................................... 31

How to Model Fuses in Transient Stability Analysis ................................................................................... 33

Examining the Results of a Transient Stability Simulation Run .................................................................. 37

Modeling of Under Load Tap Changing Transformer (ULTC) in Transient Stability ................................... 38

Motor Operated Valves ............................................................................................................................... 41

How to Model MOV in Design Bases Advanced Transient Stability Program ........................................ 42 Recommended Model Types for MOV Opening Stages ..................................................................... 46 Recommended Model Types for MOV Closing Stages ....................................................................... 47 Example of MOV Application ............................................................................................................... 50 Suggested Readings:........................................................................................................................... 53 Transient Stability Tabular Report for MOV ......................................................................................... 53

Transient Stability Post-Processing - Graphical Output Interface............................................................... 54

Import/Export of Data Between DesignBase and Excel .......................................................................... 54 How to Import Field Measured Data Into DesignBases Transient ...................................................... 56 How to Export Simulated Results Into Microsoft Excel Program ......................................................... 59

Application Guide ........................................................................................................................................ 62

How to Start a New Case ........................................................................................................................ 63 How to Model a Utility .............................................................................................................................. 64 How to Model a Partially or Fully Loaded Induction Motor ...................................................................... 73 How to Model a Generator and Its Associated Controls ......................................................................... 81 How to Model a Synchronous Motor ....................................................................................................... 87 How to Model an Induction Generator ..................................................................................................... 92


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How to Setup Transient Scenarios and Simulate Events (Disturbances) ............................................... 93 Selection of Monitored Quantities for Transient ...................................................................................... 95 Setting Base Frequencies for Asynchronously Connected Networks ..................................................... 97 Starting a Transient Simulation Run ........................................................................................................ 97

The Fault Isolation Unit (FIU) ...................................................................................................................... 98

How to Use the Fault Isolation Unit ....................................................................................................... 100

Static Automatic Bus Transfer (SABT) ...................................................................................................... 105

How to Use The Static Automatic Bus Transfer (SABT) ....................................................................... 106

The Static Frequency Converter (SFC) .................................................................................................... 112

How to Use The Static Frequency Converter (SFC) ............................................................................. 113

Transformers Inrush Current Simulation .................................................................................................. 118

Wind Farm Simulation Doubly-Fed Induction Generator .......................................................................... 123

Model Overview ..................................................................................................................................... 123 Mechanical Wind Power Characteristic ................................................................................................. 124 Reactive Power Control ......................................................................................................................... 127 Pitch Angle Control ................................................................................................................................ 129 Sample Power System Using DFIG ...................................................................................................... 130 References ............................................................................................................................................ 136

List of the Sample Test Cases .................................................................................................................. 138

Overview of User Defined Models (UDM) ................................................................................................. 140

How to build a User Defined Model .......................................................................................................... 143

How to Initialize the Variables of the Control System ............................................................................... 144

Example of a User-Defined Model for an Excitation System .................................................................... 144

Adding a User-Defined Model to the User-defined Library ....................................................................... 159

How to Use a User-Defined Model in a Power System ............................................................................ 162

How to Build a User-Defined Governor Model .......................................................................................... 165

Summary, Additional Notes, and Examples of User-defined Models ....................................................... 166

Examples of the 2nd Order Transfer Function .......................................................................................... 168

Examples of Building a Closed Loop AVR Model ..................................................................................... 170

Examples of Building the Closed loop Governor Model ........................................................................... 171

General User Defined Model (UDM) Builder ............................................................................................. 172

Testing the General UDM ......................................................................................................................... 188

Appendix A: Cyclic Load Modeling ........................................................................................................... 195


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List of Figures Page

Figure 1: Selecting Advanced Power Flow Tools ......................................................................................... 8 Figure 2: Selecting Advanced Power Flow Options ...................................................................................... 8 Figure 3: Selecting Advanced Power Flow Solution ..................................................................................... 9 Figure 4: Selecting Advanced Power Flow Report Manager ........................................................................ 9 Figure 5: Selecting Advanced Power Flow Annotation Option ..................................................................... 9 Figure 6: Selecting a Generator On the One-Line Diagram ....................................................................... 10 Figure 7: Selecting Dynamic Data for a Generator ..................................................................................... 11 Figure 8: Selecting Transient Stability Tools ............................................................................................... 11 Figure 9: Selecting Data and Event Manager for Transient ........................................................................ 12 Figure 10: Adding/Modifying Generator Dynamic Data .............................................................................. 12 Figure 11: Adding Dynamic Data for a Generator....................................................................................... 13 Figure 12: Generator Dynamic Data Dialog ................................................................................................ 14 Figure 13: Selecting Generator Model in Transient .................................................................................... 14 Figure 14: Generator Open-Circuit Saturation Curve ................................................................................. 16 Figure 15: Accessing Induction Motor Dynamic Data ................................................................................. 17 Figure 16: Alternate Method of Accessing Induction Motor Dynamic Data ................................................ 17 Figure 17: Induction Motor Dynamic Data Dialog ....................................................................................... 18 Figure 18: Defining Induction Motor Dynamic Data (Impedances and Load Torque) ................................ 19 Figure 19: Estimating Induction Motor Impedances ................................................................................... 20 Figure 20: Defining Induction Motor Characteristics Data (Testing Curve) ................................................ 21 Figure 21: Selecting Transient Stability Tools............................................................................................. 21 Figure 22: Selecting Data and Event Manager of the Transient Stability ................................................. 22 Figure 23: Adding/Modifying Events (Disturbances) in Transient ............................................................... 22 Figure 24: Selecting Supported Events (Disturbances) for Transient Analysis .......................................... 23 Figure 25: Selecting Transient Stability Tools............................................................................................. 24 Figure 26: Selecting Data and Event Manager of the Transient Stability ................................................. 24 Figure 27: Selecting Relay Models for Transient Stability .......................................................................... 25 Figure 28: Adding Relays for Transient Stability ......................................................................................... 25 Figure 29: Adding an Under Voltage Motor Relay ...................................................................................... 26 Figure 30: Selecting Motor Bus ID for Adding an Under Voltage Motor Relay ........................................... 27 Figure 31: Entering the Data for an Under Voltage Motor Relay ................................................................ 27 Figure 32: Adding an Under Voltage Line Trip Relay ................................................................................. 28 Figure 33: Defining Time-Current Characteristics of an Over Current Relay ............................................. 30 Figure 34: Selecting Relay Data from DesignBases Relay Database ....................................................... 31 Figure 35: Selecting Relay, Breaker, or Fuse ............................................................................................. 32 Figure 36: Selecting Transient Stability Tools............................................................................................. 39 Figure 37: Selecting Data and Event Manager of the Transient Stability ................................................. 40 Figure 38: Dynamic Model of ULTC in Transient ........................................................................................ 41 Figure 39: Typical MOV Illustration ............................................................................................................. 42 Figure 40: Selecting MOV from the Bus Catalog ........................................................................................ 43 Figure 41: MOV General Data Requirement ............................................................................................... 44 Figure 42: MOV Application in a Typical Nuclear Power Plant Auxiliaries System .................................... 44 Figure 43: Dynamic Data Entry for MOV Simulation .................................................................................. 45 Figure 44: Adding a MOV to the Network ................................................................................................... 45 Figure 45: MOV Dynamic Data Requirements............................................................................................ 46 Figure 46: MOV Data Requirement in the Opening Stages ........................................................................ 47 Figure 47: MOV Data Requirement in the Closing Stages ......................................................................... 48 Figure 48: Assigning MOV Model Types in each of the Five Opening Stages ........................................... 49 Figure 49: Transient Data and Event Manager Showing Completed MOV Dialog ..................................... 49 Figure 50: Dynamic Data of the Simulated MOV in the Sample System .................................................... 50 Figure 51: Starting Transient Stability Simulation Engine ........................................................................... 51


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Figure 52: Starting MOV Simulation for the Sample System ...................................................................... 52 Figure 53: Real Time Graphing for MOV Simulation .................................................................................. 52 Figure 54: Transient Simulation Result of MOV Current During Five Opening Stages .............................. 53 Figure 55: Simple System Setup for Generator Load Rejection Test ......................................................... 55 Figure 56: Selecting Transient Analysis Option - Load Rejection Test ...................................................... 56 Figure 57: Real Time Plots for the Generator Load Rejection Test ............................................................ 56 Figure 58: Bus Result for the Generator Load Rejection Test .................................................................... 57 Figure 59: Importing Measured Data Into Transient from Excel (.CSV format) .......................................... 58 Figure 60: Selecting Displays for the Monitored Variables ......................................................................... 58 Figure 61: Selecting Graphs and Charts before Exporting/Importing Data to Excel .................................. 59 Figure 62: Exporting Transient Simulation Result Data to Excel ................................................................ 60 Figure 63: Sample File Format for Imported/Exported to Excel (.CSV file) ................................................ 61 Figure 64: Sample Network Used to Illustrate Salient Features of the Transient Program ........................ 62 Figure 65: Creating a New Job file .............................................................................................................. 63 Figure 66: Selecting One-Line Diagram Electrical Template ...................................................................... 63 Figure 67: Assigning a Job file Name for the Newly Created Case ............................................................ 63 Figure 68: Password Protecting a Job file .................................................................................................. 64 Figure 69: Placing a Utility (Grid) Symbol on the One-Line Diagram ......................................................... 64 Figure 70: Providing General Data for the Utility ........................................................................................ 65 Figure 71: Proving the Short Circuit Data for the Utility .............................................................................. 66 Figure 72: Providing Load Flow Related Data for the Utility ....................................................................... 67 Figure 73: Entry to Dynamic Data Dialog for Utility and Generator ............................................................ 67 Figure 74: Confirming Dynamic Data Entry for the Generators .................................................................. 68 Figure 75: Dynamic Data Dialog for the Utility and Generator .................................................................... 69 Figure 76: Selecting a Transformer Symbol from Branch Catalog ............................................................. 70 Figure 77: Transformer General Data Dialog.............................................................................................. 70 Figure 78: Short Circuit Data Dialog for Transformers ............................................................................... 71 Figure 79: Load Flow Data Dialog for Transformers ................................................................................... 72 Figure 80: Adding a Bus Symbol on the One-Line Diagram ....................................................................... 72 Figure 81: Assigning Zone and Area to a Bus ............................................................................................ 73 Figure 82: Selecting Induction Motor Symbol ............................................................................................. 73 Figure 83: Short Circuit Data Dialog for Induction Motor ............................................................................ 74 Figure 84: Load Flow Data Dialog for Induction Motor ............................................................................... 74 Figure 85: Motor Start Data Dialog for Induction Motor .............................................................................. 75 Figure 86: Accessing the Dynamic Data Dialog for Induction Motor .......................................................... 75 Figure 87: Accessing the Transient Stability Tools .................................................................................. 76 Figure 88: Editing/Adding Dynamic Data for Induction Motor ..................................................................... 76 Figure 89: General Dynamic Data Dialog for Induction Motor .................................................................. 76 Figure 90: Equivalent Circuit Data Dialog for Induction Motor .................................................................... 77 Figure 91: Selection of Induction Motor Parameters Estimation Method ................................................... 79 Figure 92: Motor Parameters Estimation Result ......................................................................................... 80 Figure 93: Defining Motor Characteristics (Testing Curves) for Induction Motor ........................................ 80 Figure 94: Adding a Generator on the One-Line Diagram .......................................................................... 81 Figure 95: Defining General Data for a Generator ...................................................................................... 82 Figure 96: Defining Short Circuit Data for a Generator ............................................................................... 82 Figure 97: Defining Power Flow Data for a Generator ................................................................................ 83 Figure 98: Accessing Dynamic Data for a Generator ................................................................................. 83 Figure 99: Defining Dynamic Data for a Generator .................................................................................... 84 Figure 100: Selecting a Governor Model for a Generator ........................................................................... 85 Figure 101: Selecting AVR and Excitation System for a Generator ........................................................... 86 Figure 102: Adding a Synchronous Generator (Motor) on the One-Line Diagram ..................................... 87 Figure 103: Defining Synchronous Motor Power Flow Data ....................................................................... 88 Figure 104: Accessing Data and Event Manager ....................................................................................... 88


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Figure 105: Editing/Adding Dynamic Data for Synchronous Machines (Generator/Motor) ........................ 89 Figure 106: Defining Dynamic Data for a Synchronous Motor ................................................................... 90 Figure 107: Defining Dynamic Data for the Generator of an M-G Set ........................................................ 91 Figure 108: Defining Governor Model for the Generator of an M-G Set ..................................................... 92 Figure 109: Adding Induction Generator (motor) on the One-Line Diagram .............................................. 92 Figure 110: Defining Power Flow Data for an Induction Generator ............................................................ 93 Figure 111: Selecting Data and Event Manager ......................................................................................... 93 Figure 112: Adding Event to a Case Study (Scenario) ............................................................................... 94 Figure 113: Selecting an Event from the Event List .................................................................................... 95 Figure 114: Motor Starting Event Dialog ..................................................................................................... 95 Figure 115: Accessing Monitored Quantities Specifications ....................................................................... 96 Figure 116: Monitoring Generator, Motor, Bus, Branch and SVC .............................................................. 96 Figure 117: Specifying Frequencies for Asynchronously Connected Networks ......................................... 97 Figure 118: Starting Transient Stability Simulation ..................................................................................... 97 Figure 119: Examining the Graphical Result of a Transient Stability Simulation ........................................ 98 Figure 120: Fault Isolation Unit (FIU) .......................................................................................................... 99 Figure 121: Fault Isolation Unit (FIU), Normal Operation Inductor is Shorted .......................................... 100 Figure 122: Fault Isolation Unit (FIU), High Fault Current, Inductor is Inserted ....................................... 100 Figure 123: Sample Network to Demonstrate the Application of FIU ....................................................... 101 Figure 124: Adding FIU to the Power System........................................................................................... 101 Figure 125: FIU Data Entry Dialog ............................................................................................................ 102 Figure 126: Specifying the Location of FIU in the Power System ............................................................. 103 Figure 127: Sample Result - Application of FIU to Limit Fault Current in the Power System ................... 104 Figure 128: The Static Automatic Bus Transfer (SABT) ........................................................................... 105 Figure 129: SABT: Preferred and Alternate Source Operation................................................................. 106 Figure 130: Sample Network to Demonstrate the Application of SABT ................................................... 107 Figure 131: Adding SABT to the Power System ....................................................................................... 108 Figure 132: SABT Data Entry Dialog ........................................................................................................ 109 Figure 133: Sample Result for Application of SABT to Transfer Load to Alternate Source ..................... 110 Figure 134: Load Current Following SABT Transfer to Alternate Source ................................................. 111 Figure 135: The Static Automatic Bus Transfer (SABT) ........................................................................... 112 Figure 136: 6-Pulse Full Control Rectifier Used in SFC ........................................................................... 112 Figure 137: SFC Inverter Schematic ......................................................................................................... 113 Figure 138: Sample Network to Demonstrate the Application of SFC ...................................................... 114 Figure 139: Adding SFC to the Power System ......................................................................................... 115 Figure 140: SFC Data Entry Dialog .......................................................................................................... 116 Figure 141: Converter and Inverter Bus Voltages with Fault on the Inverter Side ................................... 116 Figure 142: Power Flow Through Converter and Inverter ........................................................................ 117 Figure 143: Sample Network Used for Transformer Inrush Simulation .................................................... 118 Figure 144: Selecting Dynamic Data and Event Manager ........................................................................ 119 Figure 145: Selecting Transformer Inrush Simulation (TIS) option........................................................... 119 Figure 146: Transformer Inrush Simulation Data Entry Dialog ................................................................. 120 Figure 147: Select Transient Analysis Option of the Advanced Transient Stability Program ................... 120 Figure 148: Simulation Parameters and Starting Transient Stability Program ......................................... 121 Figure 149: Detailed Graphical Displays of the Transient Stability Simulation Results ............................ 122 Figure 150: DFIG Model Controls Block Diagrams ................................................................................... 124 Figure 151: Basic Configuration of a Wind Turbine DFIG ........................................................................ 124 Figure 152: Cp, Power Coefficient as a Function of Tip Speed Ratio ...................................................... 126 Figure 153: DFIG Optimum Reference Speed Tracking ........................................................................... 127 Figure 154: Active Power And Current Control ......................................................................................... 127 Figure 155: Reactive Power Control (voltage and power factor) .............................................................. 128 Figure 156: Reactive Power Control Scheme ........................................................................................... 128 Figure 157: Pitch Angle Control Scheme .................................................................................................. 129


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Figure 158: Sample Network Used for DFIG Simulation .......................................................................... 130 Figure 159: Data Dialog of DFIG for Power flow and Short Circuit Analysis ............................................ 131 Figure 160: Selecting Dynamic Data and Event Manager ........................................................................ 131 Figure 161: Selection Dynamic Model for the DFIG ................................................................................. 132 Figure 162: DFIG Data Entry Dialog ......................................................................................................... 133 Figure 163: Selecting Analysis Option of the Advanced Transient Stability Program ............................ 134 Figure 164: Simulation Parameters and Starting Transient Stability Program ......................................... 135 Figure 165: Detailed Graphical Displays of the Transient Stability Simulation Results ............................ 136 Figure 166: Interaction between DesignBases Transient Stability and User-defined Models ................. 140 Figure 167: Partial List of the User-defined Control Blocks (functions) .................................................... 141 Figure 168: A Sample Control Block Diagram of an Excitation System ................................................... 143 Figure 169: A Sample Control Block Diagram of a Turbine System ......................................................... 143 Figure 170: Opening a New Drawing for Building a User-Defined Model ................................................ 145 Figure 171: Selecting User Defined Model Builder Type .......................................................................... 145 Figure 172: Assigning A File Naming to User-Defined Model .................................................................. 146 Figure 173: Selecting Input Block (Terminal Voltage) for AVR Model ...................................................... 146 Figure 174: Example of Drawing a User Defined Function into Draw Area .............................................. 147 Figure 175: Connecting User Defined Function Blocks Together............................................................. 147 Figure 176: Automatic Snap of User Defined Blocks ................................................................................ 148 Figure 177: Rotating a User Defined Block Using Ctrl-R key ................................................................. 148 Figure 178: Connecting and Rotating a User Defined Block .................................................................... 148 Figure 179: User Defined Constant Block Data Entry ............................................................................ 149 Figure 180: Selecting Signs for Inputs in a Summer Block ....................................................................... 150 Figure 181: Assign a Name to the Output of a Summer Block ................................................................. 150 Figure 182: Graphical Display when Inputs in a Summer Block Use Different Signs............................... 151 Figure 183: Assembling the Second Summer Block ................................................................................ 151 Figure 184: Defining a Constant Instead of a Parameter in a Lead-Lag Block ........................................ 152 Figure 185: Defining Parameters in a Lead-Lag Block ............................................................................. 152 Figure 186: Defining the 3

rd Parameter of a Lead-Lag Block ................................................................... 152

Figure 187: Adding the Lead-Lag in the AVR Control .............................................................................. 153 Figure 188: Using The Limiter Block in the AVR Control System ............................................................. 153 Figure 189: Defining the 1

st Parameter of the Limiter Function ................................................................ 154

Figure 190: Defining the 2nd

Parameter of the Limiter Function ............................................................... 154 Figure 191: Connecting the Output Block of an AVR (EFD, Field Voltage) ........................................... 155 Figure 192: Using A Connector To Tap Output Of Control Function Blocks .......................................... 155 Figure 193: Parameters of the Differentiator Block ................................................................................ 156 Figure 194: The VAR Control System Showing the 1st Feedback Block ................................................. 156 Figure 195: The VAR Control System Showing the 2nd Feedback Block ................................................ 156 Figure 196: Defining the 1

st Parameter of the Feedback Loop LEAD-LAG Block .................................... 157

Figure 197: Defining the 2nd Parameter of the Feedback Loop LEAD-LAG Block .................................. 157 Figure 198: The AVR Control System upon Insertion of the Feedback Lead-Lag Block ......................... 158 Figure 199: AVR Control When Addition Lag Block in the Feedback Loop ........................................... 158 Figure 200: Defining the Lag Block Parameters ..................................................................................... 159 Figure 201: AVR System after Connecting the Lag Block in the Feedback Loop .................................... 159 Figure 202: Completed AVR Control System ........................................................................................... 159 Figure 203: Adding User-Defined Models to the Library ........................................................................... 160 Figure 204: Screen Capture Showing How Expressions Can Be Used To Provide Initial

Output Value......................................................................................................................... 167 Figure 205: Naming Parameters of a Control Block ................................................................................. 168 Figure 206: Example of Building a 2nd Order Transfer Function ............................................................. 169 Figure 207: Example Of The Closed Loop AVR Model ............................................................................ 170 Figure 208: Example Of The Closed Loop Governor Model..................................................................... 171 Figure 209: Input/Output blocks of the General UDM and their Relationship to the Power System ........ 173


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Figure 210: Process of Building a General UDM ...................................................................................... 174 Figure 211: Creating a New Jobfile for Defining a General UDM ............................................................. 175 Figure 212: Selecting General UDM Template ......................................................................................... 175 Figure 213: Assigning the Jobfile Name for the General UDM ................................................................. 176 Figure 214: Selecting Bus Voltage Input Block from General UDM Catalog ......................................... 176 Figure 215: Placing the Bus Voltage in the Plot Area ............................................................................ 177 Figure 216: Bus Voltage Data Dialog ..................................................................................................... 178 Figure 217: Assigning Bus ID and Output Name for Bus Voltage Input Block ....................................... 179 Figure 218: Selecting Bus Frequency Input Block from General UDM Catalog ..................................... 180 Figure 219: Bus Frequency Data Dialog ................................................................................................ 181 Figure 220: Renaming the Name of Output for the Bus Voltage Block .................................................. 182 Figure 221: Renaming the Name of Output for the Bus Frequency Block ............................................. 183 Figure 222: Selecting the Division Block from the General UDM Catalog ............................................. 184 Figure 223: Connecting the Output of Voltage and Frequency Blocks to the Division Block ............ 184 Figure 224: Selecting the Lookup Function Block .................................................................................. 185 Figure 225: Saving a General UDM Model into the Library of User-defined Models................................ 185 Figure 226: Creating the Model Equation File for UDM ............................................................................ 186 Figure 227: Adding A General UDM into the Library ................................................................................ 186 Figure 228: Inspecting UDM Model Parameters and Assigning Model Descriptions. .............................. 187 Figure 229: Testing the General UDM Models ......................................................................................... 188 Figure 230: Adding a General UDM Model to the System ........................................................................ 189 Figure 231: Selecting a General UDM Model from the UDM Library........................................................ 190 Figure 232: Data Entry Dialog for the General UDM ................................................................................ 190 Figure 233: Starting Transient Stability Simulation ................................................................................... 191 Figure 234: On-Line Plotting in the Transient Stability Program............................................................... 192 Figure 235: Tabular Results of the General UDM .................................................................................... 193 Figure 236: Single Line Diagram of Power System used Cyclic Load Modeling ...................................... 195 Figure 237: Selecting Cyclic Load Event .................................................................................................. 196 Figure 238: Cyclic Load Data Dialog ........................................................................................................ 197

List of Tables Page

Table 1: Data Requirements for Supported Generator Models .................................................................. 15

Note: You can view this manual from your CD as an Adobe Acrobat PDF file. The files name is:

Advanced Transient Stability Adv_Trans _Stability.pdf

Important Notes: Advanced Transient Stability handles long bus ID names up to 24 alphanumeric characters. It is

recommended, however, that you use 14 characters. If you use more than 18 characters your branch current

will have more than one line.

Power Analytics Corporations software products are tools intended to be used by trained professionals only. They are not substitutes for your professional judgment or for independent verification and testing of results

as they pertain to your specific application. Use of all Power Analytics Corporation software products is

governed by the terms and conditions of the End-User License Agreement (EULA) you accepted when purchasing and installing the software. You must comply with these terms and conditions in applying the

instructional material in this manual. If you do not have or are unfamiliar with the contents of your EULA

for this software, you should request, read, and understand a copy of your EULA before proceeding.


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Important Product Function Announcement

Security Index Calculation in the Advanced Transient Stability Program

Traditional transient stability programs such as those offered by the majority of power system analysis software

vendors, are capable of accurately computing the trajectories of power system quantities (e.g. voltages, frequencies,

power flows, etc.) following disturbances. While all other vendors have left the understanding of these trajectories

(i.e., severity of these disturbances) and their relevance to the power system security largely to the engineers judgment!

Power Analytics, contrary to other software vendors, not only computes fast and accurate power system trajectories

but also provides the engineers with the overall system security index simply by giving a mark between 0 and 100 to

the security. A security index of 100 means the system is fully secure following the disturbances, while a security

index of 0 indicates insecurity following the disturbance.

In the Power Analytics DesignBase transient stability program three different indices are computed, namely, voltage stability index, frequency stability index, and angular (transient) stability index. These indices are then

combined to arrive at total system security index.

Angular (Transient) Stability Index Power Analytics DesignBase software computes this index based on Angle Separation. DesignBase uses a heuristic method which has proven to be very effective both in terms of computational speed and accuracy. The

transient stability index for each island in the power system is computed. The stability index for the system is taken

as the smallest index among all islands.

Frequency Stability Index

The frequency stability index is defined as the maximum time duration for which the frequency excursion

(rise/drop) violates the predefined threshold.

Voltage Stability Index

The voltage stability index is defined as the maximum time duration for which the voltage excursion (rise/drop)

violates the predefined threshold.

System Security Index

The overall system security index is defined as the multiplication of the aforementioned indices. That is, for the

power system to be declared secure, all of the above indices should be greater than zero.

There are several enhancement and additional have been implemented in this release of the DesignBase Advanced

Transient Stability Program. The main added features are:

Transient Stability Index Dynamic Model for Breakers Dynamic Model for Fuses Library Manager Combining the standard AVR/excitation models with the user defined models into one list


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Combining the standard governor models with the user defined models into one list Echo of user defined models parameters in the report file

Dynamic models for breakers and fuses are similar to the relay models. The user can select breakers and fuses from

the devices in the database or those used in the Protective Device Coordination program.

A dynamic device library manager (for generator, exciter, and governor) has been added to facilitate selection of

generator, exciter and governor models in a study. The user can also modify default value of the parameters as well

as their upper and lower range.

Details of the above enhancements are discussed in the manual (see the table of contents).

Advanced Transient Stability Capabilities, Features and Functions

Unlimited Physical Bus Modeling Unlimited number of dynamic models in system Trapezoidal Integration Technique Import Test and Field data for comparison of actual vs. simulation Transformer Inrush Model Changing Mechanical Torque of Induction Motors MG-Set Simulation Dynamic ULTC simulation Integrated Control Logic Modeling and Simulation User Defined Control Logic Modeling System with full on-board oscilloscope Real-time Simulation Frequency Dependent Machine and Network Models Real-time Display of Results on the One-Line Diagram Multi Speed Motor Simulation Static Automatic Bus Transfer Simulation Comprehensive Windmill Model Doubly Fed Induction Generator Model Fault Isolation Unit Static Frequency Converter Integrated Event Manager Multiple CK# between two buses Simulate negative torque Simulate relay actions Fault Cables and Transmission lines at any length User defined actions including CB operation Automatic Load Shedding Variable Time Simulation (Short Time and Long Time) Events and Actions Unlimited Time Events & Actions Simulate any Combination of System Disturbances & Operations Induction/Synchronous Motor/Generator Dynamic Models Frequency Dependent Machine and Network Models Extensive Dynamic Machine Models Phase-shifting transformer


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Synchronous motor exciter/AVR system User-defined Dynamic Models (UDM) interface for: Exciter/AVR Governor - Turbine Power System Stabilizer Complete integration with User-Defined Dynamic Models for the Generator Start-Up Analysis IEEE & Selected Manufacturer Exciter, Governor, & Power System Stabilizer Models for Generator Comprehensive Exciter and Governor Models Direct communication with Protection Coordination program to obtain device settings Automatic CB operation based on instantaneous relay settings Over current (50) Voltage (59/27) Frequency (81) Impedance Relay Simulation Directional Over current (67) Reverse Power (32) Motor Overcurrent (50M) Solid State Trip (SST) User-Customizable Plots with Option to Overlay Plots for machine terminal impedance (for out-of-step relay setting) Plots for branch flows (MW, Mvar, MVA, and Amps) MOV Starting Motor Acceleration Motor Load Modeling Loss of excitation action Critical Fault Clearing Time and System Islanding Time Fast Bus Transfer Studies Impact Loading & Generator Rejection Motor Soft Starters, Delta-Y Starter, External R Starter, Auto-Transformer, etc. Motor Point-by-Point Load Model Transformer LTC Initial & Operating Time Delays SVC (Steady-State & Transient Response) HVDC Link Universal Relays Synchronous Motor Acceleration with Discharge Resistor & Pull-in Process Step & Ramp Generation Changes Step & Ramp Generator AVR Reference Voltage Changes Step & Ramp Loading Changes for Synchronous & Induction Motors Line-to-Ground Faults System Zoning & Automatic Reference Machine Assignment for Each Islanded Subsystem Absolute Power Angle for Synchronous Generator & Synchronous Motor Mvar for Synchronous Generator, Synchronous & Induction Motors Terminal Voltage for Synchronous & Induction Motors Difference of Variables Contactor Open & Close Action Start Synchronous Motor & Induction Machine by Starting Category Multi-Mass Shaft Model for Generators & Motors Transient Stability Index


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Introduction to Advanced Transient Stability

The DesignBase Advanced Transient Stability program is a simulation software program for assessing the dynamic

behavior of electrical power systems when subjected to disturbances. The program can be used for a number of

applications including but not limited to:

a. Motor starting and motor sequencing. An example is the assessment of adequacy of a power system in

emergency start up of auxiliaries in nuclear power plants.

b. Design and evaluation of the protections such as under frequency and under voltage load shedding

schemes. Example of this is allocation of required load shedding for an assumed loss of generation in

electrical utilities or even on a ship.

c. Determination of critical clearing time of circuit breakers to maintain stability.

d. Design of special protection systems.

The Transient Stability Program is time-domain simulation software, and its required data can be divided into two

categories:

System Static Components. The static elements are transformers, cables, overhead lines, reactors, capacitors, etc.

(sometimes referred to as non-rotating equipment). The term static means that these elements are assumed to display

no changes during the time in which the transient disturbance takes place. The time frame for such a disturbance

ranges from cycles up to a few seconds. This static information is the basis for what is called the power flow

solution.

Rotating Equipment. This group encompasses synchronous machines including their associated controls (exciters,

governors, etc), induction machines, static var compensators, etc.

This program, therefore, solves two types of equations simultaneously: one similar to the power flow program and

one for the dynamic equations of controllers and machines. The following power system components are supported

by the DesignBase advanced transient stability program:

Synchronous Machines: generators and/or motors. Thermal (round rotor) and hydraulic (salient pole)

units can be both simulated either by using a simple model or by the most complete two-axis including

damper winding representation.

Induction Machines: motors and/or generators. A complete two-axis model can be used. Also it is

possible to model them by just providing the testing curves (current, power factor, torque as a function of

speed). In the latter case, there will be no electrical dynamics modeled.

Doubly Fed Induction Generator: With the increased use of wind power, particularly in wind-farms, the

voltage and frequency behaviors of the power system networks are likely to be affected significantly.

Doubly Fed Induction Generator (DFIG) is mainly used for wind energy conversion in MW range power

plants. DFIG has a rotor inverter and a front-end converter while the stator is linked directly to the power

system. Design Base has incorporated state of the art models for Doubly Fed Induction Generator in both

Design Bases advanced power flow and transient stability simulation programs. The DFIG transient stability model is comprehensive with highly flexible control system.

Motor Operated Valve (MOV): A motor operated valve (MOV) is commonly used in the nuclear power

plant auxiliaries operation as well as other industrial installations. The reliable and safe operation of MOV

depends on several important operational parameters including 1) Ascertain availability of sufficient

voltage, 2) Development of required torque, 3) Development of necessary trust. When assessing the


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capability of the emergency startup of the auxiliaries of a nuclear power plant, it is commonly required to

model MOV operation. Two modes of MOV operation are of interest, namely, opening and closing

operating modes. Each mode of operation consists of five distinct stages. For example, the opening mode

comprise of: a) Start, b) Full Speed, c) Unseating, d) Travel, and e) Stall. To accurately account for the

modeling of the aforementioned stages, DesignBases Transient Stability program supports a user-defined model types for each of the stages. Thats start can be modeled as constant current while full speed may be modeled by constant power, etc. The same flexibility exists for the five stages of the closing mode

AVR and Excitation Systems: There are a number of models ranging from rotating (DC and AC) and

analogue to static and digital controls. In addition, the DesignBases Transient Stability program offers a user-defined modeling capability, which can be used to define a new excitation model.

Governors and Turbines: There are a number of models covering all types of units including hydraulic,

Diesel, gas, and combined cycle with mechanical and/or digital governors. In addition, the DesignBase

Transient program offers a user defined modeling capability that can be used to define a new

governor/turbine model.

Relays: including under frequency, under voltage, over current and impedance type can be simulated.

Static Var Compensators (SVC): supported for a number of solid-state (thyristor) controlled SVCs or even the saturable reactor type.

Fault Isolation Unit (FIU): also known as Current Limiting Device (CLD), is a device installed between

the power source and loads to limit the magnitude of fault currents that occur within loads connected to

power distribution networks. The FIU limits the bus voltage loss caused faults, or excessive loads, and thus

prevents damage or loss of other equipment. Without the FIU protection, faults could create currents of

thousand amperes thus exceeding the capabilities of the power system equipment. FIU with its high-speed,

three-phase, solid state electronic switch, is capable of inserting a current-limiting impedance in all three

lines of a three phase power circuit within 25 micro-seconds from the onset of load current exceeding its

limit. If the fault/load current is higher than a threshold, then within 80 milliseconds, the FIU can send a

shut trip signal to trip the associated load circuit breaker. DesignBase transient supports the detailed

modeling of FIU.

Static Automatic Bus Transfer (SABT): is a solid-state three-phase, dual position, three-pole switch

consisting of six pairs of silicon controlled rectifier (SCR) connected in an AC switch configuration. Three

pairs of the SCR (one pair per phase) are connected to the normal (preferred) input power source, while the

other pairs are connected to the alternate source. Both input sources are continually being monitored for

out-of-tolerance conditions (e.g. low or loss of voltage) and when an abnormal condition is sensed on the

normal source the switch transfer, in very fast (~4 msec), to the alternate source. Subsequently, if the

normal source returns to within normal tolerance, the SABT automatically transfers from the alternate

source back to the normal source. SABT model is fully supported in the DesignBases transient program.

Supported Events (Disturbances)

The power system behavior can be assessed under a number of different disturbances (events) as outlined below:

Application/removal of three-phase fault. Application/removal of phase-to-ground fault. Application/removal of phase-phase fault. Application/removal of phase-phase-ground fault. Branch Addition.


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Branch Tripping with/without automatic reclosing. Starting Induction Motor. Stopping Induction Motor. Shunt Tripping. Shunt Addition (Capacitor and/or Inductor). Generator Tripping. SVC Tripping. Impact Loading (Load Restoration). Changing Mechanical Torque on Induction Machine. With this option it is actually possible to

turn an induction motor to an induction generator.

Manual Load Shedding & Load Restoration Cyclic Load

The program can be used to simulate multiple simultaneous, or sequenced in time events (disturbances).

Required Steps to Run Transient Stability Program

Step 1.

As mentioned before, the static data of electrical power system should be supplied and Power Flow analysis must be

performed. It is important to remember that every time static data are changed Power Flow should be re-run

before starting the transient simulation. It is not necessary to run power flow if only dynamic data (such as

exciter gain, machine inertia, etc.) or events are changed. If faults, other than 3-phase faults, are to be simulated,

then a short circuit analysis must also be performed before starting a transient simulation.

Prior to running a transient simulation, one should examine the power flow result and make sure that the system

conditions are within acceptable steady state operation limits; i.e. voltages are within 95-105% and there are not

severely overloaded lines/cables/transformers: the generators are not producing or absorbing reactive power

outside their reactive power capability, the active power generation is within the turbine capability, etc. The

Transient Stability program will not produce any meaningful result if already in steady state (power flow solution)

extreme abnormal operating conditions exist.

Step 2.

Enter the dynamic models for the generators, exciters, turbines, governors, induction machines, relays, etc. The

preferred approach (just recommended but not necessary) is to first enter the generator data by themselves, and

execute a Transient Analysis run without simulating an event (applying any disturbance). Under these circumstances

one must verify that all parameters (voltages, power flows, angles, etc.) remain constant as function of time. Next,

add the data for controls (exciters, governors, etc.). It is wise not to use complex control model if sufficient data

for it are not available. It is better to use a simpler model with good data than having a complex model and bad

data. Recall the rule of Garbage in, Garbage out!

Step 3.

After adding control data (exciter, governor, etc.) run the Transient Analysis for the second time without applying

any disturbance. Again, all monitored quantities should remain constant over the time.

Step 4.

Now that the data have been tested, select the desired event(s) and perform the simulation. Carefully examine the

result of the transient program by plotting the monitored quantities (voltages, frequency, line flows, etc.). Pay close

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attention to the tabular report, check and correct modeling deficiencies as required. For example, if a fault has been

applied, then, the generator field voltage should increase when terminal voltage has fallen (provided an exciter has

been defined for the machine). If the machine has sped up, then, the mechanical power should decrease (provided a

governor has been defined for the machine).

What to Do When the Simulation Terminates Abnormally:

1. Examine the report file. See any warnings, or errors, that may appear in the report. Correct the errors and re-run the program.

2. If a motor starting case is being examined, make sure the solution integration step is 0.004 or smaller.

3. If a control contains high gain and small time constants it may be necessary to use an integration step as small as 0.004 or smaller.

4. If a message to the effect that "Load Flow Diverged" appears in the report file, one of the following solutions may help solve the problem:

4a. Ensure that the convergence tolerance of the solution is not too small. Normally the tolerance

in the transient program is the same as the tolerance defined in the power flow program. However,

it is not uncommon to specify a bit larger tolerance in the transient program.

4b. Ensure that an unrealistic situation has not been created. For example, the load exceeds the

spinning reserve, or the governors are undersized, etc.

4c. Ensure that the dynamic data have been entered correctly. Do not enter a zero value for the

parameters of the control blocks that would make the problem numerically unstable. For example,

for a control block of 1/(KE+sTE) do not set KE to zero. If this is the case then try to see if other

models can be used where the control block is actually 1/sTE or enter a small value for KE (e.g.

0.001).

4d. Ensure that the integration time step is not too large. Normally, select a value close to 0.017

seconds (1 cycle in 60 Hz system) unless a motor starting scenario is being examined where a

value of 0.004 seconds is more appropriate.

4e. Ensure that dynamic data, at least for the important generators and utility generator (swing)

have been properly entered.

4.f Make sure that the important generators; buses, branches and motors are monitored. Do not use a

very large, or, a very small reporting step. Normally, select the reporting step to be a few cycles

(0.033 seconds)

4.g Increase the number of iteration from its default of 100.

Data Entry

As previously indicated, make sure that the static data are entered correctly and the power flow program has been

run before performing a transient analysis. Also make sure that the Load Flow solution of the power system seems

reasonable. There is no practical benefit in running a Transient Stability analysis on a system with abnormal power

flow conditions. Below is a summary of how the power flow options and solution can be selected. Open the drawing

file OCRELAY, under the transient sample folder. Select the Power Flow icon, as shown below, to activate the Power Flow tools:

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Figure 1: Selecting Advanced Power Flow Tools

Then the following options (icons) will appear:

a) The Power Flow solution option gives the choice of a solution method, convergence tolerance, etc.

Figure 2: Selecting Advanced Power Flow Options

b) Solve the power flow:


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Figure 3: Selecting Advanced Power Flow Solution

c) Examine different reports:

Figure 4: Selecting Advanced Power Flow Report Manager

d) Select the annotation options:

Figure 5: Selecting Advanced Power Flow Annotation Option


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Using the above options, select solution options and parameters and solve the power flow. Examine the power flow

result and if the result is satisfactory, then proceed to the data entry process for the transient program.

Entering the Generator Data

To enter dynamic data for the generators double-click left mouse button on the generator bus as shown in Figure 6:

Figure 6: Selecting a Generator On the One-Line Diagram

Then, on the Description tab select the Machine "Dynamic Data" button as shown in Figure 7:


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Figure 7: Selecting Dynamic Data for a Generator

Alternatively, use the Data and Event Manager by first selecting Transient Stability Tools as shown below:

Figure 8: Selecting Transient Stability Tools

and then Data and Event Manager as shown in Figure 9:


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Figure 9: Selecting Data and Event Manager for Transient

Once the Data and Event Manager is selected (as in Figure 9), the following dialog will appear:

Figure 10: Adding/Modifying Generator Dynamic Data

Now click the right mouse button (on the Machine) to get the option of adding a machine (generator), see Figure 11:


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Figure 11: Adding Dynamic Data for a Generator

The generator dynamic data dialog, as shown in Figure 12, will appear. The selection of Machine type should be based on two factors: a) if machine is Salient or round rotor, b) and on the amount of available data.


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Figure 12: Generator Dynamic Data Dialog

To select a generator model use the dropdown menu shown in Figure 13:

Figure 13: Selecting Generator Model in Transient

The machine data include impedances and time constants. A real synchronous machine cannot have neither zero

impedances nor zero time constants. Therefore, do not enter any zero values for them. Also make sure that the

machine power base MVA is correctly entered and all of the impedances data that have been entered are in percent on the generator base MVA. The machine inertia constant is normally a value between 0.5 and 20 MW-

sec/MVA (or simply the unit of inertia constant is second). For utility (not a real generator which represents an

equivalent power system) select Eq Constant Model with MVA rating same as the utility fault level, and enter X'd = 100%. For the inertia constant, a value of 99 seconds is normally sufficient.

If a machine is round rotor (thermal units), then, the direct and quadature impedances are usually equal. For salient pole

machine (hydraulic) units, the direct axis impedances are greater than their quadature axis counterparts. Also the

synchronous impedance is greater than transient impedances, and transient impedances are greater than sub transient

impedances. The largest time constant is T'd0 (i.e., Xd>Xd>Xd>Xl and Td0>Td0). For the AVR and excitation system, make sure the proper model type is selected. If the model type is known, but the parameters are not

available, it is better to select a simpler model having only a few parameters rather than using the correct model

but with wrong or incomplete data. Make sure the gains and time constants are entered correctly. If you are uncertain

about the parameters contact the DesignBase customer support center for advice. The AVR gain can have a wide

range depending on its type. It can be as low as 20 and as high as 1000 pu. The time constants are long when rotating and

analogue controllers are used, but much shorter for digital controllers.

For governors and exciters use models that can closely represent the system under study when correct parameters are

available. Otherwise, use a very simple model. The range of governor droop normally varies between 0.02 - 0.10

p.u. (or governor gain of 50-10). Higher values can be expected in thermal units. Make sure that for the governor

models, where applicable, the turbine rating is entered and its value should be close to the generator MVA

rating. Also, maximum and minimum outputs must be entered correctly. For example, if in the power flow solution

the generator is giving its maximum output, the maximum turbine output should not be set to a much lower value.

The turbine and governor time constants are much higher for thermal units with hydraulic governors than for gas

turbines with digital governors.

Summary of Generator Types and Data Requirements

Table 1 (below) summarizes the required data for each synchronous machine model supported by the transient

stability program:


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Table 1: Data Requirements for Supported Generator Models

Parameters Generator Type

Eq Constant

Eq Eq, Eq, Ed Eq, Ed Eq,Eq,Ed,Ed

MVA

Inertia Constant

Damping factor

Direct-axis transient reactance

Quadrature-axis transient reactance

Direct-axis reactance

Quadrature-axis reactance

Potier reactance

D-axis transient open-circuit time constant

Q-axis transient open-circuit time constant

Saturation data S2

Saturation data S1

Saturation data E2

Saturation data E1

D-axis sub-transient reactance

D-axis open-circuit sub-transient time

constant

Q-axis open-circuit sub-transient time

constant

Q-axis sub-transient reactance

The required data for each generator type is marked with symbol in the above table. All of the above generator impedances should be expressed in percent on the generator MVA base defined earlier. For the convenience of the users, the inertia constant (expressed in seconds) can be given by alternate data, i.e. the program will compute the

inertia constant from the moment of inertia, WK2 (expressed in lb-ft

2), generator speed, RPM (expressed in

revolution per minuets) and generator base power (MVA) as follows:

MVAGen

RPMRPMWKHtConsInertia

.

***10*311525.2tan

210

Finally, the generator saturation coefficients S1 and S2 defined corresponding to the generator terminal voltages E1

and E2, respectively can be computed from the generator open-circuit test as shown in Figure 14:


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Figure 14: Generator Open-Circuit Saturation Curve

Utility Model in the Transient Stability

As mentioned earlier, the utility or equivalent generator can be represented by Eq constant model. For the sake of simplicity, it is also recommended that MVA base shown in the above table for the utility be the same as 3-phase

fault level (expressed in MVA). Then, the Direct-axis transient reactance becomes100% or 1.0 p.u. The inertia

constant can be much higher than the real generators. For example, a value of 99 for inertia constant is appropriate

in most cases.

Induction Machine and Data Requirements in the Transient Stability Analysis

To enter dynamic data for the induction motor, open the Drawing file LOADRAMP form the transients sample folder and then select the Motor Dynamic Data button in the Description tab as shown in Figure 15:

E1

E2

Saturation Factors Defined At Terminal Voltages E1 And E2


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Figure 15: Accessing Induction Motor Dynamic Data

Or alternatively, select the M symbol as displayed in Figure 16:

Figure 16: Alternate Method of Accessing Induction Motor Dynamic Data

There are two models for representing induction motors in the transient program. The first model is a complex

model based on the DQ axis theory, and requires motor impedances as input data. In Figure 17, this is shown as

Equivalent Circuit:


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Figure 17: Induction Motor Dynamic Data Dialog

The second model is based on the motor characteristic named Testing Curves, also shown above. It uses the motor characteristics, such as: power factor, current, torque a function of speed (slip), which is normally provided by

the manufacturer or obtained from field tests. This model does not have any transient associated with rotor or stator

voltages. The induction motor data under General tab shown in the above screen are required for both models. Note that in the lower part of the above figure, the Motor Starter applies only to the power flow and not to the transient simulation. However, the user can obtain motor current, power factor, and torque from a power flow

simulation with different starters, and then provide these data in the fields of Testing Curves tab and change the Simulation Method to Testing Curve and perform a transient analysis.

If the motor is to be modeled by the Equivalent Circuit, then, selecting the Equivalent Circuit tab shown above, will display the required data dialog as shown in Figure 18:

If the rotor and stator impedances are available, then, these impedances should be given in ohms. The rotor cage

factors Kr and Kx will take into account the rotor resistance and reactance dependencies on slip (speed) variations.

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Figure 18: Defining Induction Motor Dynamic Data (Impedances and Load Torque)

These factors are defined as follows:

1)(@

)0(@

speedfullRr

speedRrKr 1

)(@

)0(@

speedfullXr

speedXrKx

These factors also account for a double cage rotor construction. If motor impedances are not available, then, select

Calculate, shown in the middle of above screen and the following menu will appear:


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Figure 19: Estimating Induction Motor Impedances

Motor impedances can be estimated by two different methods, as shown in the above figure. First, by just specifying

the locked rotor data as shown in the lower part of the above figure, second, by using the data specified in the

Testing Curve dialog. In either case, the program will try to calculate impedances such that the error between specified conditions (locked rotor or motor characteristics) and computed conditions is minimized. The weighting

factors should only be changed if the user wishes to weight some part of data more than the other (for example

current more than power factor). The Testing Curve data can be provided in the following dialog.

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Figure 20: Defining Induction Motor Characteristics Data (Testing Curve)

The user can enter up to 100 data points. The Testing Curve data shown in Figure 20 can be used in two different ways. First, motor impedances can be estimated using the above data. Second, the above-specified motor

characteristics can be used directly to represent the motor.

Simulating Events (Disturbances)

When studying a power system under disturbance(s) it is a good idea not to initiate the first event (disturbance) at

time zero. The reason for this is to allow the system to reach a steady state condition before a disturbance is applied.

If this steady state condition cannot be reached, it means that the data are not correct. Such situations occur if the

power flow has not been solved before running transient, the maximum output of the governor(s) is less than power

flow solution, the exciter or AVR minimum output has been specified to be smaller than the requirement of the pre-

disturbance value. To add an event, first select the Transient Stability Tools icon as shown in Figure 21.


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Then, select Data and Event Manager as shown in Figure 22.

Figure 22: Selecting Data and Event Manager of the Transient Stability

Figure 23 shows data and event options:

Figure 23: Adding/Modifying Events (Disturbances) in Transient

To add an event, click the right mouse button to choose Add One Event option. Then, the list of supported events will appear as shown in Figure 24:


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Figure 24: Selecting Supported Events (Disturbances) for Transient Analysis

A number of events can be simulated in the transient program including four types of faults, branch tripping, load

restoration, etc.

Changing Mechanical Torque of an I tion Machine

DesignBases Advanced Transient Stability Program offers unique capabilities to simulate a number of events that have become of paramount importance in the recent years due to ever increasing complexity of the power systems.

One example of the supported events simulations is changing of the induction machine load torque during transient

simulation with user-defined times and amount. Simulation of change of induction machine torque may be required

in several scenarios, the most obvious being in representation of variable wind speed in the simulation of wind farms

(induction generators). Another application is the simulation of reversal of water flow in pumps used in submarine

operations.


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Relay Models In Transient Stability

Then representation of protections in transient stability simulation is an important consideration in todays system studies. DesignBases Advanced Transient Stability program supports a number of different relays including:

Impedance Relay used to protect a line (by tripping it) when a fault is detected on it; Under Frequency Load Shedding Relay used to shed load as frequency is declining to different levels

below rated frequency. In this type of relay only static load can be shed;

Under Voltage Load Shedding Relay used to shed load as voltage is declining to different levels below rated voltage. In this type of relay only static load can be shed;

Under Voltage Motor Relay used to trip a motor if the voltage falls below a specified threshold (like magnetic contactors operation);

Under Voltage Line Relay used to trip a line if the voltage falls below a specified threshold; Under Frequency Motor Relay used to trip a motor if the frequency falls below a specified threshold; Under Frequency Line Relay used to trip a line if the frequency falls below a specified threshold; Over Current Relay: This relay protects the line against any excess current flow in the inverse-time

characteristics.

For example open the transient UNDERVLOTAGERELAY sample file. To add a relay, first select the Transient Stability Tools icon as shown in Figure 25. Then, select Data and Event Manager as shown in Figure 26.


Figure 26: Selecting Data and Event Manager of the Transient Stability

Now, select relay by clicking the left mouse button on the Relay until it is highlighted, as shown in Figure 27.


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Figure 27: Selecting Relay Models for Transient Stability

Then, click the right mouse button to add one relay model to the power system at hand, as shown in below.

Figure 28: Adding Relays for Transient Stability

For example, use the pull-down to select the Under Voltage Motor Relay as shown in Figure 30.


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Figure 29: Adding an Under Voltage Motor Relay

Use the drop-down in the Motor Bus ID to select the desired motor where you wish to place the under voltage motor relay as shown in Figure 30.


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Figure 30: Selecting Motor Bus ID for Adding an Under Voltage Motor Relay

The relay operating time and breaker operating time can be given as shown in the above Figure.

Figure 31: Entering the Data for an Under Voltage Motor Relay


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Similarly, an under voltage line trip relay can be entered. Figure 32 shows the data dialog screen for under voltage

line trip relay.

Figure 32: Adding an Under Voltage Line Trip Relay

Important Notes:

1) There are two under voltage relays: one is for the opening line and the other for tripping induction motors. The

under voltage motor relay can be accurately used to represent the magnetic contactors which are used on most

industrial induction motors. Also, there are two under frequency relays: one is for opening the line and the other for

tripping induction motors. The data required for the under voltage relays are:

Voltage threshold below which line/motor will be tripped. The voltage threshold should be given in p.u. The default value is 0.88 p.u.

Relay Operation time in second. This is required time for the relay to sense the under voltage condition including any intentional delay. Default is 0.2 seconds;

Breaker opening time in seconds. Default is 0.1 second.

The principle of operation of these under voltage or under frequency relays is the same, and they open line/motor if:

the voltage (frequency) at the motor bus (or line sending terminal) is below the threshold. Then a timer will be


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started, and once the relay operating time is expired, then, after the breaker opening is elapsed, the motor/line will be

tripped. Note that once the voltage (frequency) is below the threshold for relay operating time, even if the voltage

(frequency) recovers, the line/motor will still be tripped.

2) Make sure that for under-frequency load shedding relays the frequency set points are entered correctly. For

example, the first stage frequency is normally 59.3 Hz (in 60 Hz system) the percentage of load shed in the first

stage may be as high as 100%. The second stage is 59.0, and third stage is 58.7 Hz. These set points are just typical,

but they should be used as guideline when the correct data are not available. For under voltage relay the set point is

normally 88% voltage. Also, the relay time and breaker time is normally 6 cycles for each. Longer times are used for

electromechanical relays or when additional time delays are required.

3) The settings for impedance relays are much more difficult to generalize. These settings are normally found by

running transient programs for different fault locations and durations. A careful examination of the impedance seen

by the relay will reveal the required setting values.

How to Model Over Current Relay in Transient Stability Analysis

Over current relays are supported in the DesignBases Transient Stability Program. The program uses the time-current characteristics of a relay to determine if the breaker should open the protected line under disturbances such

as faults.

The main screen for defining time-current characteristics of an over current relay is shown in Figure 33.


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Figure 33: Defining Time-Current Characteristics of an Over Current Relay

There are three ways to define the time-current characteristics of an over current relay as shown in the above Figure:

From PDC: If a Protective Device Coordination study is performed for the network in question, then, select From PDC button. From Relay DB: User can brows through the comprehensive DesignBases relay database, and select the desired relay, as shown in Figure 34, or simply enter the relay data points as shown in Figure 33. Note that

the 10 current data points should be in ascending order.


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Figure 34: Selecting Relay Data from DesignBases Relay Database

How to Model Breakers in Transient Stability Analysis

Breaker models are now supported in the DesignBases Transient Stability Program. The program uses the time-current characteristics of a breaker to determine if the breaker should open the protected line under disturbances

such as faults. To use a breaker in a study select breaker from the Data and Event Manager as shown in the next figure:


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Figure 35: Selecting Relay, Breaker, or Fuse

To add a breaker press left mouse click on the breaker as shown below:

The main screen for defining time-current characteristics of a breaker is shown below:


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There are three ways to define the time-current characteristics of breaker as shown in the above Figure: From PDC: If a Protective Device Coordination study is performed for the network in question, then, select From PDC button. From Breaker DB: User can brows through the comprehensive DesignBases breaker database, and select the desired breaker, or simply enter the breaker data points in the fields of Time and Current. Note that the 10 current data points should be entered in the ascending order.

How to Model Fuses in Transient Stability Analysis

Fuse models, similar to breakers and relays, can be used in the Transient Stability Program. The program uses the

time-current characteristics of a fuse to determine if the fuse should open the protected device under disturbances

such as faults. To use a fuse in a study select Fuse from the Data and Event Manager as shown in Figure 35. To add a breaker press left mouse click on the Fuse and choose Add One Fuse. The main screen for defining time-current characteristics of a fuse is shown below:


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As seen above, there are three ways to define the time-current characteristics of fuse; From PDC: If a Protective Device Coordination study is performed for the network in question, then, select From PDC button. From Fuse DB: User can brows through the comprehensive DesignBases fuse database, and select the desired fuse, or simply enter the fuse data points in the fields of Time and Current. Note that the 10 current data points should be entered in the ascending order. Below the steps required to select a fuse from the database is illustrated. From the above select From Fuse DB and program will prompt the user to select a Manufacturer as shown below:


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Use the dropdown to browse through list of fuse manufacturers and shown below:


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For example, in the above GEC has been selected. Then, fuse type can be selected similar to the selection of the manufacturer by using the dropdown.

After selecting fuse type, fuse rating can be selecting by browsing through available ratings for the selected fuse type and

manufacture as shown below:

Now the t

adv trans stability

Documents

data requirements

generator data

data entry

utility model

induction machine

supported events disturbances

simulating events disturbances

current relay