Edsa Paladin

Advanced Electromagnetic Transient Analysis Program

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Capacitor EnergizationABC

EDSA MICRO CORPORATION 16870 West Bernardo Drive, Suite 330

San Diego, CA 92127 U.S.A.

© Copyright 2008

All Rights Reserved

Version 3.10.00 October 2008

EDSA MICRO CORPORATION WARRANTY INFORMATION

There is no warranty, implied or otherwise, on EDSA software. EDSA software is licensed to you as is. This program license provides a ninety (90) day limited warranty on the diskette that contains the program. This, the EDSA User’s Guide, is not meant to alter the warranty situation described above. That is, the content of this document is not intended to, and does not, constitute a warranty of any sort, including warranty of merchantability or fitness for any particular purpose on your EDSA software package. EDSA Micro Corporation reserves the right to revise and make changes to this User's Guide and to the EDSA software without obligation to notify any person of, or provide any person with, such revision or change. EDSA programs come with verification and validation of methodology of calculation based on EDSA Micro Corporation's in-house software development standards. EDSA performs longhand calculation and checks the programs’ results against published samples. However, we do not guarantee, or warranty, any program outputs, results, or conclusions reached from data generated by any programs, which are all sold "as is". Since the meaning of QA/QC and the verification and validation of a program methodology are domains of vast interpretation, users are encouraged to perform their own in-house verification and validation based on their own in-house quality assurance, quality control policies and standards. Such operations - performed at the user's expense - will meet the user's specific needs. EDSA Micro Corporation does not accept, or acknowledge, purchase instructions based on a buyer's QA/QC and/or a buyer's verification and validation standards. Therefore, purchase orders instructions are considered to be uniquely based on EDSA's own QA/QC verification and validation standards and test systems. TRADEMARK EDSA is a trademark of EDSA Micro Corporation. COPYRIGHT © Copyright 1989 - 2008 by EDSA Micro Corporation. Please accept and respect the fact that EDSA Micro Corporation has enabled you to make an authorized disk as a backup to prevent losing the contents that might occur to your original disk drive. DO NOT sell, lend, lease, give, rent or otherwise distribute EDSA programs / User's Guides to anyone without prior written permission from EDSA Micro Corporation. All Rights Reserved. No part of this publication may be reproduced without prior written consent from EDSA Micro Corporation.

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Table of Contents 1. Overview ................................................................................................................................................1 2. Component Modeling.............................................................................................................................2 3. Introduction ............................................................................................................................................3 4. Sources of Transient Overvoltages .......................................................................................................3 5. Principles Transient Overvoltage Protection .........................................................................................4 6. How to Run the EMTAP Program..........................................................................................................6 7. Setting up Switching Events in EMTAP.................................................................................................9 8. References...........................................................................................................................................22

List of Figures Figure 1: Transient Calculations of Lightning and Switching Surges.........................................................1 Figure 2: Equivalent Networks for Example 1 ............................................................................................2 Figure 3: Equivalent Networks for Example 2 ............................................................................................2 Figure 4: Protection Principles ...................................................................................................................5 Figure 5: Diagram of the Sample Power System Used for Capacitor Energization Study ........................6 Figure 6: Starting the DesignBase Program...............................................................................................7 Figure 7: Opening Sample Jobfile for Capacitor Energization Study (CAPMAG-EMTAP.AXD)................7 Figure 8: Starting EMTAP Program............................................................................................................8 Figure 9: EMTAP Program ICONs .............................................................................................................8 Figure 10: Switching Event Manager ICON .................................................................................................9 Figure 11: Analyze ICON of the EMTAP program .......................................................................................9 Figure 12: Main Switching Event Manager Dialog .....................................................................................10 Figure 13: Adding a Switching Event to a Case/Scenario..........................................................................11 Figure 14: Specifying Switching Time in a Case/Scenario.........................................................................11 Figure 15: Specifications of Switches in Close/Open Event ......................................................................12 Figure 16: Selecting Phases Involved in the Close/open Event.................................................................12 Figure 17: Selecting Open or Close Action in a Switching Event...............................................................13 Figure 18: Defining Open/Close Times of Switches...................................................................................13 Figure 19: Main Analysis Dialog of EMTAP ...............................................................................................14 Figure 20: Main Dialog for Selecting Desired Monitored Buses and Branches .........................................15 Figure 21: Selecting Buses and Branched for on-line Plotting...................................................................16 Figure 22: Selecting a Case Study from List of defined Cases for Analysis ..............................................16 Figure 23: On-Line Plotting of Bus Voltage and Branch Current ...............................................................17 Figure 24: Sample Text Report of the Monitored Quantities......................................................................18 Figure 25: Detailed Plots of the Selected Bus Voltages/Branch Currents .................................................19 Figure 26: Plotting RMS Values of the Selected Bus Voltages..................................................................20 Figure 27: Detailed Plots of the Selected Branch Currents........................................................................21 Figure 28: Detailed Plots of the Individual Phases for the Monitored Quantities .......................................21 Note: You can view this manual on your CD as an Adobe Acrobat PDF file. The file name is:

Advanced Electromagnetic Transient Analysis Program EMTAP.pdf You will find the Test/Job files used in this tutorial in the following location:

C:\DesignBase2\Samples\EMTAP=Advanced Electromagnetic Transient Analysis Program

ALL RIGHTS RESERVED COPYRIGHT 2008

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1. Overview Electromagnetic transient analysis of power systems is one of the most crucial power system studies. Its main objective is to study the fast transients to power systems caused by switching surges and lightning strikes. Figure 1 below shows examples where electromagnetic transient analysis is required. Example 1 shows a lightning strike on a transmission line 3 km away from a substation. Example 2 shows a surge of energy in a high voltage transmission line with the receiving end being opened when line is energized. In example 1, engineers can apply the analysis to find out lightning overvoltages in the substation in order to install arresters to protect equipment from lightning damage. In example 2, engineers can apply the analysis to find out switching overvoltages at the receiving end in order to coordinate the insulation level and size reactors to control overvoltages.

Example 1: One-Line Diagram of System for Lightning Surge Study

Example 2: System One-Line Diagram for Switching Surge Study due to Line Energization

Figure 1: Transient Calculations of Lightning and Switching Surges

EDSA Electromagnetic Transient Analysis Program (EMTAP) is designed to assist electrical engineers to solve electromagnetic transient problems of complex power systems. There are two major approaches in analyzing the transients in power systems, time-domain and frequency domain approaches. With the time-domain approach the power system transient is analyzed in time-domain and the solution of the transient for the system is expressed in terms of voltage distributions at discrete times. Nonlinear components and switch operations can be easily handled with this approach. On the other hand, with the frequency-domain approach the solution for the power system transient is found at discrete frequencies first and converted to time-domain with inverse Fourier transformation. With this approach, frequency dependent parameters of power system components, such as those of transmission lines and underground cables, can be easily considered. However, it is difficult with this approach to handle switch operations and nonlinear components. EMTAP uses time-domain approaches. It models all of the power system components (e.g. generators, cables, transformers, etc.) into equivalent impedances with current sources. Then nodal analysis is applied to get the nodal matrix of the network with nodal voltages being the unknown variables and current sources being the exciting functions. By solving the linear equations, the nodal voltages at the one time step become known, and the current sources for the next time step are calculated. Then the time step is incremented and next loop starts. The loop will proceed until the total time period interested is covered. The solution for the transient of the system is expressed in terms of voltage and current values at all the discrete time points. Selection of the time step depends on the nature of the transients. The time step is typically in the order of micro seconds for the lightning surge study and in the order of milliseconds for the switching surge study.

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2. Component Modeling Transient calculation is usually needed in high voltage power systems, as the ratio of the cost to the insulation level of the system is quite high as compared to lower voltages. To calculate the electromagnetic transient in the high voltage system, the low voltage distribution subsystems connected to the high voltage system are usually ignored (surge impedances will limit the distances that fast transients can travel). In lightning surge transient calculation, one of the main objectives is to study the impact of incident lightning waves along a transmission line on the equipment of a substation. Transformers are usually of the biggest concern, since they could be damaged by overvoltages caused by incident lightning waves. In such a study, most part of the substation is omitted and transformers are simplified as well. The transmission lines and arresters are the major components to be modeled in the study. In switching surge transient calculation, the low voltage distribution subsystems are converted to Thevenin equivalent circuits represented by series impedances and voltage sources seen by the high voltage system. In this process, transformers are usually taken into consideration, and, therefore, removed from the resulting network. All the components in the high voltage systems will be modeled in the switching surge studies. It is important to note that EDSA’s Advanced Electromagnetic Transient Analysis Program is capable of handling large size power system thereby eliminating the need to simply the power system under study.

Figure 2: Equivalent Networks for Example 1

Figure 3: Equivalent Networks for Example 2

EDSA’s Advanced Electromagnetic Transient Analysis Program (EMTAP) is a time domain based power system analysis tool. In order to model a power system in the time domain, all of the power system components (generators, cables, over head lines, transformers, loads, etc.) converted into the

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fundamental elements R, L, and C along with the transformation of the currents and voltages into their respective time domain values. Voltages and currents are transformed into their per-phase instantaneous values. All of the components defined in the power system are represented in phase domain (three phase system). This approach enables the user to examine transients due to switching of specific phase(s), for example, only one phase of three phase capacitor bank may be closed. The EMTAP computes instantaneous values of voltages and currents in the power system. For example, if the RMS Line to Line voltage is 13.8 kV, then, the instantaneous voltage (line-ground) is:

)cos(11.267)cos(3/8.13*2)( φφ +=+= wtwttV The same concept is used to change the currents into instantaneous time domain values. 3. Introduction The word transient has been used in the analysis of power systems to indicate an undesirable event that is usually momentary in nature. Power engineers, when they hear the word transients, think of a damped oscillatory type transient produced by a RLC network. Another term in use by power engineers is surge. When power engineers think of surge they tend to associate it with lightning strikes for which a surge arrester is used for protection. The term transient is also associated with other terms such as sags, swells, and interruptions. In broad terms, transients can be classified into two categories, impulsive and oscillatory. An impulsive transient is a sudden, non-power frequency change in the steady-state condition of voltage, current, or both, that is unidirectional in polarity (primarily either positive or negative). The most common cause of impulsive transients is lightning. Due to the high frequencies involved, the shape of the transient waveform can quickly change due to network components. Also, impulsive transients can have significantly different characteristics when viewed from different parts of the power system. This type of transient usually excites the natural frequency of the power network and produces oscillatory transients. An oscillatory transient is a sudden non-power frequency change in the steady-state condition of the voltage, current, or both, that includes positive and negative polarity values. Oscillatory transients consist of voltage, current, or both voltage and current, whose instantaneous values change polarity very rapidly. These transients are defined by their frequency. Oscillatory transients with a primary frequency of over 500 kHz and of short duration (milliseconds) are considered high frequency and are often the result of a local network response to a lightning strike. Medium frequency oscillatory transients (caused by lightning stroke, cable switching, or multiple capacitor switching) are between 5 and 500 kHz, and can be measured in tens of microseconds. Low frequency oscillatory transients are typically caused by capacitor switching (although there are many other causes) and are less than 5 kHz and last up to fifty microseconds. 4. Sources of Transient Overvoltages The two main types of transient overvoltages on utility systems are capacitor switching and lightning strikes. Capacitor switching: Capacitor switching is one of the most common occurrences on a utility system. Capacitors provide voltage support and supply reactive power, which helps to reduce losses in transmission. The problem with capacitors is that they interact with the inductance of the power system and create oscillatory transients when they are energized.

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Typically, when capacitors are switched into the network the initial voltage across the capacitor is zero. Since capacitor voltage cannot change instantaneously, the bus voltage where the capacitor is located is momentarily pulled down to zero and then rises with the capacitor voltage back to the system voltage. But, for typical capacitors in inductive power systems, the capacitor voltage overshoots and oscillates at the natural or resonant frequency of the system. This overshoot voltage can be as high as 2 per unit depending on the power system damping, but typically is in the 1.3 to 1.5 per unit range. If power factor correction capacitors are located at a customer bus (usually on the customer side of the utility transformer) the overvoltage transient can propagate through the transformer and be amplified by nearly the amount of the turn ratio of the transformer. This is a consequence of certain types of low-voltage capacitors and step-down transformers whose impedance forms a natural frequency at or near the switching frequency of the switched capacitor. There are two economical methodologies that can be used to reduce these capacitor-switching transients. Method one is for the utility to switch the capacitor via a synchronous breaker or switch/switches with pre-insertion resistors. Method two is to insert surge arresters at the customer location in order to limit the transient voltage magnitude. Lightning Strikes: Lightning is one of the most potent sources of impulsive power system transients. Lightning can strike the primary phase and/or ground, secondary phase and/or ground, or some type of grounded structure. A strike to this type of equipment can result in lightning currents being conducted from the power system into industrial loads. The most common conduction path is a direct strike to the phase or secondary conductor. Very similar over-voltages can be observed from lightning current flowing through ground conductors. A note here that strikes to the primary phase can be conducted to the grounding network through the arresters located on the service transformer. While most of the surge current is eventually dissipated into the ground network nearest the strike point, a substantial amount of the surge current will circulate to other ground points during the first few microseconds of the lightning strike. There are many ways that lightning induced transient overvoltages can enter an industrial power system. One way for the transient to enter is via the capacitive coupling of the service transformer. The surge is so fast that the inductance of the transformer blocks the first part of the wave from passing through the turn ratio, but the inter-winding capacitance offers a ready path for the high frequency wave. This permits the existence of a secondary voltage that is greater than the turns ratio would suggest. This type of capacitive coupling would depend greatly on the inherent design of the service transformer. Another way that the transient can enter the load is via the grounding network located at the service transformer. This can present a problem if the grounding network of the load offers a smaller resistance to the surge current than the utility ground system. Thus the surge current flows through the ground conductors of the load on its way to ground. 5. Principles Transient Overvoltage Protection There are several fundamental principles of overvoltage protection of load equipment including:

Limit the voltage across the sensitive insulation Divert surge currents away from loads Block surge current from entering the load Bond ground references together at the equipment Reduce/prevent surge current from flowing between ground points Create a low-pass filter using limiting and blocking principles.

These principles are illustrated in Figure 4. The main function of surge arresters and transient voltage surge suppressors is to limit the voltage that can appear between two points in the network. Therefore, arresters need to be placed directly across the sensitive insulation that is to be protected so that the voltage seen by the insulation is limited to a safe value. Surge suppression devices should be located as

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near as possible to the critical load/insulation with a minimum lead length. In Figure 4, arrester no. 1 is connected at the service entrance between the phase conductor and the neutral-ground bond. This arrester provides a low impedance path for surge current to travel to ground. Thus this arrester acts to divert the surge current away from the sensitive load/insulation.

Figure 4: Protection Principles

In Figure 4 there is another path in which the surge current can enter the sensitive load/insulation; the external signal cable that is bonded to the local ground. If the ground conductor of the signal cable is connected to another grounded device (and this is usually the case) located in another area, there can be a substantial amount of surge current flowing in that ground cable. The surge arrester located at the service entrance is electrically too remote for this condition. Therefore, another arrester (arrester # 2) is connected directly across and as close as possible (this arrester can sometimes be placed in the control panel itself) to the sensitive load. What is needed in the ground network is for all ground reference conductors be bonded to one point on the load equipment. This is not to prevent the local ground reference from rising in voltage potential due to the surge, but to ensure that all ground references in that vicinity rise together. Blocking techniques usually focus on high frequency surge current generated by lightning strikes and capacitor switching events. Since normal power currents must pass unhindered through such blocking schemes, it is difficult and expensive to build filters that can distinguish between low frequency surge currents and power frequency currents. High frequency blocking schemes usually consist of an inductor or choke placed in-line (in series) with the load. Thus the high frequency voltage will be dropped across the inductor before it reaches the sensitive loads. The blocking function of the series inductor is sometimes combined with the voltage limiting function of the arrester to form a low pass filter. Figure 4 shows such a circuit naturally occurring when arresters are placed on both ends of a line feeding a load. The inductance forces the majority of the surge into arrester # 1 while arrester # 2 simply cleans up the surge residue.

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6. How to Run the EMTAP Program In this section step by step procedure for running the EMTAP program is described. An example is used to illustrate the program operation. The focus of this example is to study the potential effects of utility capacitor switching transients using EDSA’s EMTAP program. The example will cover the particular case in which the customer’s power system is tuned close to the natural resonance frequency of the utility’s switching event. Critical areas of a customer’s plant and the utility power distribution system have been modeled in order to determine the severity of the switching transients, as well as the magnification effect caused by in-plant Power Factor Correction (PFC) capacitors. The plant is fed at 27.6kV from the local utility substation located at 2 miles distance from the plant. The incoming 27.6 kV feeder is step down to 600 Volts, via a 1.5 MVA transformer with a short circuit impedance of 5.74%. The 600 Volt substation is also equipped with a 500 kVAR switchable Power Factor Correction capacitor bank. The jobfile “capmag-emtap.axd” shows a detailed model of the system under analysis. Capacitors are used by the local utility to regulate voltage levels and to reduce reactive power flow in the system. When capacitors are switched on, the initial current surge causes a notch in the voltage (a sub-cycle voltage drop). As the voltage rises back to its nominal peak, it may overshoot to levels that can reach and even exceed 200% of nominal values. Steady state is reached after a period of voltage oscillation. The frequency of this transient is rather low (tends to range between 200 Hz and 1.5 kHz). The magnitude, duration, and frequency of this oscillatory transient will depend on many factors such as load damping, system inductance, and possible resonant conditions in the system, etc. When this transient reaches a capacitor bank circuit tuned at or near its oscillation frequency, it will be amplified causing problems to customers at the receiving end. The single-line diagram for the system modelled in “capmag-emtap.axd” is shown in Figure 5:

Figure 5: Diagram of the Sample Power System Used for Capacitor Energization Study

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HOW TO START EMTAP Start DesignBase by double clicking on the program ICON as shown below:

Figure 6: Starting the DesignBase Program

After starting the DesignBase program, either create a new job file by selecting the File|New command, or open an existing jobfile by selecting the File|Open command. Here open the sample jobfile as shown below:

Figure 7: Opening Sample Jobfile for Capacitor Energization Study (CAPMAG-EMTAP.AXD)

To start EMTAP, from the main screen of the DesignBase program, select Analysis -> EMTAP as shown in Figure 8:

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Figure 8: Starting EMTAP Program

The EMTAP program ICONs are shown in Figure 9 below. The first ICON is “Options”.

Figure 9: EMTAP Program ICONs

The next icon shown below is “Switching Event Manager”, here the close/open times of switches defined in the power system can be specified.

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Figure 10: Switching Event Manager ICON

And finally, to start an electromagnetic transient simulation, select the “Analyze” ICON of the EMTAP program as shown in Figure 11:

Figure 11: Analyze ICON of the EMTAP program

7. Setting up Switching Events in EMTAP Simulation of electromagnetic transient event such as capacitor energization, lighting strikes, cable energization, etc. is essentially specification of times at which switches are closed (sometime opening of a switch may be used). To specify the close/open times for different switches/breakers defined in the power system, select “Switching Event Manager” ICON. The event dialog is shown below:

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Figure 12: Main Switching Event Manager Dialog

To the lower left part of the above dialog, four ICONs are shown, namely, “Add Case” (to create a scenario/case), “Copy” and “Remove” (to copy or delete a scenario/case), and “Edit” to edit an existing case. In the middle part of the above dialog, three ICONs are shown, these are, “Add Event” and “Remove” (to specify close/open times for switches in a case/scenario or deleting a switch in a case), “Edit” is used to modify the open/close time of switch.

From Figure 13 dialog, it can also be seen (in the left part), that a case/scenario named “24 MVAR CAP Energization” has been specified. Only one breaker has defined for this case (shown in the right part of Figure 13). The closing time for all of the three phases is specified to be at t=0.01667 seconds. The breaker, once closed, connects buses MAIN and CAP24MX.

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Figure 13: Adding a Switching Event to a Case/Scenario

To add an event, Press “Add Event” ICON button as seen in Figure 13 (see the arrow in this figure). Once “Add Event” is selected, the list of available switches/breakers defined in the network will be shown (see also the single line diagram of the sample system shown in Figure 5 for the location of switches). The list of switches are shown below:

Figure 14: Specifying Switching Time in a Case/Scenario

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It can be seen in the above dialog, that it is possible to define:

Close/Open Phase involved And time of action (close/open)

In this example, three phases of the breaker between buses MAIN and CAP24MX will closed at 16.67 milliseconds as shown below:

Figure 15: Specifications of Switches in Close/Open Event

To specify which phases are involved in the close/open event, select dropdown seen below “Phase” in the below figure (the choices are ABC, AB, AC, BC, A, B, and C phases):

Figure 16: Selecting Phases Involved in the Close/open Event

The dropdown shown next to the “Action” can be used to select the type of switching action (either close or open) as seen in Figure 17.

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Figure 17: Selecting Open or Close Action in a Switching Event

The time at which the switching action to take place is defined in the last field shown in Figure 18.

Figure 18: Defining Open/Close Times of Switches

After defining the desired switching action in our scenario, we move on to analysis activity. Select “Analysis” ICON as was shown in Figure 11. The main analysis dialog of the EMTAP is shown in Figure 19:

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Figure 19: Main Analysis Dialog of EMTAP

There are several simulation parameters that are required before initiating a transient run. From the upper right part of the above dialog, it can be seen that simulation times may be defined in either millisecond or second. Normally the selection of unit of time in millisecond is more convenient than second. Below, time unit, we need to define total simulation time (of course based on the time unit selected, this may entered in either millisecond or second). Next, the solution time step (integration time step) should be defined. For example, in 60 Hz system, 1 cycle is 16.666 milliseconds. Now if the simulated phenomenon is extremely fast, then, we should be using something in order of a few microseconds. Below the integration step, a choice is provided to examine the results in either per unit or voltage/current in kV/kA. It also possible to obtain the result in some multiples of the integration step. This may be useful especially when extremely small integration step is used. EMTAP simulation usually produces large volume of result which makes it impractical to monitor all buses and lines/cables, etc. in the power system. It is also important to note that as we move away from the location of switching events, the transient quickly dies off which alleviate the need to monitor far away locations from the event. Due to aforementioned, the user should carefully select the monitored quantities. Normally there is no need to monitor a large number of buses and branches. To specify the desired quantities for monitoring, select “Select Component(s) to Display” ICON as shown in the right side of the above figure. The main dialog for the selecting monitored quantities is shown in Figure 20:

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Figure 20: Main Dialog for Selecting Desired Monitored Buses and Branches

In the dialog shown to left side of the above screen capture, there are two tabs shown, one for selecting buses and the other for selecting branches. To select buses of interest, simply double left mouse button on the desired bus will put the bus to the right side “Selected Buses”. Similar process is used for selecting branches. Once the required monitored quantities are specified, maximum up to two buses and two branches can be selected for “on-line” plotting. The “on-line” plotting refers to graphing the bus voltage and branch current as the program computes them. I.e., at every solution time step, the result up to that time will be shown on the plot. Therefore, the on-line plots continue dynamically until total simulation time is reached. To select buses for on-line plots, use the dropdown shown next to the “Bus:” as shown in Figure 21.

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Figure 21: Selecting Buses and Branched for on-line Plotting

The same procedure is used for selecting the branches for on-line plotting. Before staring a transient simulation, a scenario should be selected from the list of defined scenarios. This is only relevant if more than one scenario has been defined. To select the desired scenario, use the dropdown shown in Figure 22.

Figure 22: Selecting a Case Study from List of defined Cases for Analysis

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Figure 23: On-Line Plotting of Bus Voltage and Branch Current

Press the “Start Simulation” button to begin transient run for the selected scenario as shown in the above figure. As simulation progresses in time, the plots of bus voltages and branch currents will be updated upon completion of each solution time step. Once the simulation is completed, the result of the selected quantities may be examined in tabular format. A Sample text report is shown below.

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Figure 24: Sample Text Report of the Monitored Quantities

The detailed plots for all of the selected buses and branches can be viewed. To examine the results in graphical form, select “View Graphic Results” button as shown in Figure 23. The detailed graphical result dialog is shown in below figure. There are two tap shown in Figure 25, “Bus Voltage” and “Branch Current”. The result for each selected quantity can be displayed in the instantaneous or RMS values. The user may switch back and forth between RMS and instantaneous value by using the radio buttons shown in this figure.

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Figure 25: Detailed Plots of the Selected Bus Voltages/Branch Currents

To plot voltage at a different bus, simply select the desired bus by right mouse click on its ID shown in upper right part of the above figure. Once the RMS display option is selected the selection of phase will be disabled. The reason is that the RMS value is computed according to the following relationship:

0.3/)()()()( 222icibiaiRMS tVtVtVtV ++=

Where: Va, Vb, and Vc are phase a, b, and c voltages at time ti The RMS value for the selected bus is shown in Figure 26. Note that the RMS values of bus voltages are expressed in line-line and not line to ground.

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Figure 26: Plotting RMS Values of the Selected Bus Voltages

Similar to plots for bus voltages, the selected branch currents can be examined in the graphical form. Simply select “Branch Current” tab as shown in Figure 27.

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Figure 27: Detailed Plots of the Selected Branch Currents

Figure 28: Detailed Plots of the Individual Phases for the Monitored Quantities

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8. References [1] Dommel, H.W. "Digital Computer Solution of Electromagnetic Transients in Single and

Multiphase Networks," IEEE Trans. Power App. Syst., vol. PAS-88, pp.338-399, April 1969. [2] Legate, A.C. "Comparison of Field Switching Surge Measurements with Transient Network

Analyser Measurements," IEEE Trans. on Power App. Syst., vol. PAS-90, pp.1347-1354, May/June 1971.

[3] A. Greenwood "Electrical Transients in Power Systems” Second Edition, John Wiley &

Sons, Inc., 1991 [4] Marti, J.R. "Accurate Modeling of Frequency-Dependent Transmission Lines in

Electromagnetic Transient Simulations," IEEE Trans. on Power App. Syst., vol. PAS-101, pp.147-157, Jan. 1982.

[5] Wedepohl, L.M. and Wilcox, D.J. "Transient Analysis of Underground Power Transmission

Systems: System-Model and Wave Propagation Characteristics," Proc. IEE, vol. 120, pp.252-259, Feb. 1973.

Edsa Paladin

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edsa micro

incident lightning

sample power

capacitor

power frequency

high voltage

power system