Implementation Of Emtp/Atp Software In The Study Of Electromagnetic Transient Phenomenon

Electromagnetic Transient Phenomenon deals with the study of high voltage transients in power systems due to lightning, switching and traveling waves. However, it is not easy to visualize the effects of transients in power systems merely from transient analysis equations. Electromagnetic Transient Program/Alternative Transients Program (EMTP/ATP) is a general purpose software for simulating transient phenomena in power systems and for power system analysis. The plotting facility of the program makes it an excellent tool for understanding and visualizing the effects of transients in power systems. However, it is not easy to use EMTP/ATP. The paper explains a method of developing input modules for various components and illustrates the ease and effectiveness of using these modules for power system analysis using EMTP/ATP. INTRODUCTION Switching, lightning or faults may cause transients in power systems. To study these transients by using a digital computer necessitates the development of mathematical models that describe the transient behavior of the system. EMTP/ATP is powerful software developed to model and simulate both the steady state and transient behavior of power systems . The software incorporates simple equivalent networks for all the components in the power system. The system behavior is simulated through nodal analysis of the system equivalent network. EMTP/ATP is however, not very user-friendly. A full-fledged graphical user interface for the software is yet not available. The rulebook for this software is 800 pages long and a novice user can easily get frustrated using the software. Traditionally, an EMTP/ATP data file has to be structured so that power system data is grouped by classes, e.g. data (cards) for switches, branch impedances and sources. This makes it very difficult to track errors and maintains data for changes in the system. As a result the data file creation and editing becomes very cumbersome. There are, however, two options 5,6 available to users to overcome the above problem. The first option allows the user to mix the data classes by using the “/” cards, e.g. the /BRANCH, /SWTCH, /SOURCE, etc. Using these cards, the user can group the components of different classes, which are geographically close in the power system. Even though this option helps in the creation and debugging of the data file, the user still has to be well aware of the rules of creating the data file using the element templates for the different elements in a power system. The second option available to the user is the data modularization. This option allows the novice user to start using the software in minimum time and evaluate transient phenomena of a power circuit. Once the input module files for the various components are available, all the user has to do is to learn to incorporate the module punch files for the components in a data file and run the P ge 317.1 file using EMTP/ATP. The user does not need to study the rule book and know an element’s template to create a data file or make changes. DATA MODULARIZATION An EMTP/ATP input module can be thought of as a component consisting of one or more elements of the same or different data classes. EMTP/ATP input modules can be created by using the individual element templates and the available supporting subroutine called DATA BASE MODULE. The input modules have arguments just like the subroutines in a FORTRAN program. These module files can be stored as ordinary files and run using the EMTP/ATP program. The resulting module output files are called “ punch files " and they are used to create the data file needed for analysis. The punch files have a .PCH extension. The punch files for various components of the system are included in a data file by using the $INCLUDE statement followed by the punch file name and a list of arguments that describe the component. The procedure for creating the input module files is given in the Appendix. Fig. 1. Schematic diagram for a resistor element The comment cards in EMTP/ATP start with the letter “C” in the first column with the second column being blank. The input module file (1R.DAT) and the punch file (1R.PCH) for the element in Figure 1 are shown below. Input module file : 1R.DAT BEGIN NEW DATA CASE -NOSORT --C Module for a resistor. C USAGE: INCLUDE, 1R,FRNODE,TONODE,VALUER,H DATA BASE MODULE $ERASE ARG,FRNODE,TONODE, ARG,VALUER,H NUM,VALUER,H DUM, /BRANCH C 0 FRNODETONODE VALUER H C ^^^^^^^^ BEGIN NEW DATA CASE C Just one comment card only, since the KASEND in "startup" file is 1. $PUNCH BEGIN NEW DATA CASE BLANK