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Alternative Transient Program (ATP)

ATP is a universal program system for digital simulation of transient phenomena of electromagnetic as well as electromechanical nature. With this digital program, complex networks and control systems of arbitrary structure can be simulated.

ATP has extensive modelling capabilities and additional important features besides the computation of transients. It has been continuously developed through international contributions over the past 20 years.

Operating Principles

  • Basically, trapezoidal rule of integration is used to solve the differential equations of system components in the time domain.
  • Non-zero initial conditions can be determined either automatically by a steady-state, phasor solution or they can be entered by the user for simpler components.
  • Interfacing capability to the program modules TACS (Transient Analysis of Control Systems) and MODELS (a simulation language) enables modelling of control systems and components with nonlinear characteristics such as arcs and corona.
  • Symmetric or unsymmetric disturbances are allowed, such as faults, lightning surges, any kind of switching operations including commutation of valves.
  • Calculation of frequency response of phasor networks using FREQUENCY SCAN feature.
  • Dynamic systems also can be simulated using TACS and MODELS control system modelling by itself.


  • Uncoupled and coupled linear, lumped elements.
  • Transmission lines and cables with distributed and frequency-dependent parameters.
  • Elements with nonlinearities: transformers including saturation and hysteresis, surge arresters, arcs, corona.
  • Ordinary switches, time-dependent and voltage-dependent switches, statistical switching (Monte-Carlo studies).
  • Valves (diodes and thyristors).
  • 3-phase synchronous machine, universal machine.

Simulation Language MODELS

MODELS in ATP is a general-purpose description language supported by an extensive set of simulation tools for the representation and study of time-variant systems.

  • The description of each model is enabled using free-format, keyword-driven syntax of local context and that is largely self-documenting.
  • MODELS in ATP allows the description of arbitrary user-defined control and circuit components, providing a simple interface for connecting other programs/models to ATP.
  • As a general-purpose programmable tool, MODELS can be used for processing simulation results either in the frequency domain or in the time domain.

Supporting Routines

  • Calculation of electrical parameters of overhead lines and cables using program modules LINE CONSTANTS, CABLE CONSTANTS and CABLE PARAMETERS.
  • Generation of frequency-dependent line model input data.
  • Calculation of model data for transformers.
  • Saturation and hysteresis curve conversion.
  • Data modularization (for $INCLUDE).


  • Time-varying output in printed lists, character plots, or vector plots using separate interactive graphic programs TPPLOT, PCPLOT, PlotXY. HP-GL and PostScript also can be produced.
  • Postprocessing of monitored variables using MODELS and/or TACS, Fourier analysis.

Hardware Requirements

Most users, including program developers, use Intel Pentium based PC's with Ms-Windows 3.x/95/NT/XP. A standard PC configuration with 64 MB RAM, hard disk (30 MB free space) and VGA graphics is sufficient to execute ATP under MS-DOS/MS-Windows. ATP is available for other computers, too.

Maximum Capabilities

ATP-EMTP tables are dimensioned dynamically at the start of execution to satisfy the needs of users and their hardware (e.g., RAM). No absolute limits have ever been observed, and the standard version has limits that average more than 20 times default table sizes. Today, the largest simulations are being performed using MS-DOS computers.

Default table sizes:

Busses 3000
Branches 3000
Switches 1200
Sources 340
Nonlinear elements 460
Synchronous machines 45

Additional Tools

ATPDraw for Windows

ATPDRAW is a graphical, mouse-driven preprocessor for ATP on the MS-Windows 9x/NT/XP platforms. Using ATPDraw for Windows, one builds a graphical picture of an electric circuit by picking objects from menus, connecting and editing objects, and keying data interactively. ATPDRAW then creates the corresponding ATP input data file. The user can create his own circuit objects by using the Data Base Module feature of ATP.


An interactive graphical output tool under MS-DOS/MS-Windows 3.x/95 with extensive features such as mouse support, menus, window plotting, Fourier analysis, COMTRADE format, HPGL, PostScript output, superposition of different plots, X-Y plot, simple MATH operations and more.


A simpler interactive graphical output tool available separately as DOS program and 32-bit program PCPlot for Windows 95/NT with features such as HPGL output, screen copy, zoom function, etc.

About Us

This site has been established for the users of the royalty-free ATP version of the Electromagnetic Transients Program (EMTP). The ATP license is free for nearly everyone accepting the rules expressed in written form when filling the license form.

The site is maintained by the Europan EMTP-ATP users group. There are other related web-sites:

Our Partners:


ATP Draw  

Japanese ATP User Group

 CAUE - Comité Argentino de Usuarios del EMTP/ATP

User Groups  


User Support

User support is available through two mailing lists:

ATP-EMTP-L for licensed-only-users
EEUG-L for members of the users group

When logging into this Website, you have access to a

moderated Forum



last but not least, use This email address is being protected from spambots. You need JavaScript enabled to view it.

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