EMTP and Line Constants (LC)

The features of EMTP and Line Constants Program given below are similar to a program developed by M/s Microtran Power System Analysis Corporation, with the exception that available software will not handle Power Electronics Circuits, ideal transformers and rotating machines. Details of EMTP and Line constant features, the technical documents, user documents and a free student limited edition of the Microtran software can be down loaded from the web site http://www.microtran.com.

General Features of EMTP and LC

• Lumped R, L, C elements.
• Multiphase pi-circuits.
• Single and three-phase n-winding transformers.
• Transposed and untransposed distributed parameter transmission lines with constant or frequency dependent parameters.
• Nonlinear resistances and surge arrester models (including metal oxide arresters), as well as nonlinear inductances with user-defined residual flux.
• Switches with any number of opening/closing sequences, and other switching control criteria to simulate circuit breakers with multiple closing- opening sequences, spark gaps, etc.
• Diodes, thyristors, and anti-parallel thyristor models with either fixed, or user-defined firing controls.
• Voltage and current sources. In addition to standard mathematical functions (sinusoids, surge functions, steps, ramps), the user may specify sources point by point as functions of time, or calculate them inside the user-supplied subroutine SOURCE.
• Synchronous machines with armature, field, and damper windings. The model also includes a shaft- mass system representation for the simulation of torsional oscillations.
• Initial conditions can be determined automatically by the program or they can be supplied by the user. The program can also be used to obtain steady-state phasor solutions at a given frequency or over a user-defined frequency range. The "frequency scan" capability is particularly useful for harmonics, resonance and subsynchronous resonance studies.
• User-supplied linear or nonlinear models using the entry point routine CONNEC. The procedure is quite simple: the user compiles his version of CONNEC with any compiler capable of creating a DLL. A sample version of CONNEC and detailed interface information is available to would-be developers.

Switching Transient Studies

These studies are generally performed to assess the transients associated with:

• Energization of overhead transmission lines and study of associated transients, surge arrester ratings, transient mitigation methods.
• Energization of capacitor banks / reactors in industrial or public utility facilities.
• Transients associated with various switching actions such as fault application and clearance.

Insulation Coordination

Insulation Coordination is the process of determining the proper insulation levels of various components in a power system as well as their arrangements. It is the selection of an insulation structure that will withstand voltage stresses to which the system or equipment will be subjected to, together with the proper surge arrester. The process is determined from the known characteristics of voltage surges and the characteristics of surge arresters.

The following standards are used by the consultants, while performing the insulation coordination:

• Insulation Co-ordination, Part 1: Definitions, principles and rules – IEC 71-1, standard.
• Insulation Co-ordination, Part 2: Application guide – IEC 71-2, standard.
• IEEE Guide for the Application of Insulation Coordination. IEEE Std 1313-2-1999.

Summary of Application of EMTP Studies*

EMTP is used world-wide for switching and lightning surge analysis, insulation coordination and shaft torsional oscillation studies, protective relay modeling, harmonic and power quality studies, HVDC and FACTS modeling. Typical EMTP studies are:

• Lightning overvoltage studies
• Switching transients and faults
• Statistical and systematic overvoltage studies
• Very fast transients in GIS and groundings
• Machine modeling
• Transient stability, motor startup
• Shaft torsional oscillations
• Transformer and shunt reactor/capacitor switching
• Ferroresonance
• Power electronic applications
• Circuit breaker duty (electric arc), current chopping
• FACTS devices: STATCOM, SVC, UPFC, TCSC modeling
• Harmonic analysis, network resonances
• Protection device testing