EMTP for Power Transmission System

Features

The perfect tool for the simulation of large, modern and complex power systems.

Load-flow solution

Multiphase and unbalanced load-flow are available in EMTP to determine network solutions and steady-state phasors. Time-domain simulation is automatically initialized from load-flow. Therefore, EMTP does not require to be linked with any external load-flow solver. All the simulations are conducted within the same environment.

Temporary over-voltages

Transient phenomena like earth fault, load rejection and switching of nonlinear equipment that can be analysed with EMTP are the main causes of temporary over-voltages.

Figure 2 shows voltages at the terminals of an unloaded transformer. This is a typical case of temporary over-voltage (energization of unloaded transformer) simulated in EMTP.

Figure 1: 3-phase voltage in transformer terminals in p.u

Switching over-voltages

Transient overvoltages that occur when switching power system equipment (capacitor banks, transmission lines, transformers…) can be estimated using EMTP.

Figure 2: Transient over-voltages in p.u when switching a capacitor bank

Lightning over-voltages

EMTP features advanced options to simulate transients resulting from lightning strikes as shown in Figure 5.

Figure 3: Lightning strike on 230 kV transmission lines system

EMTP includes accurate line and cable models which take into account the frequency dependence of parameters. Surge arresters ratings and locations can be determined using EMTP to protect equipment from lightning overvoltages.

Transient stability

Transient stability analysis enables users to accurately model power system dynamics by simulating system disturbances and other events.

Figure 4: 3-phase power of machines presented in Figure 7 – Simulation of LL-g permanent fault

EMTP offers the most accurate machine models due to its Newton based interfacing methods and predictor solution.

Figure 5: transient stability case of 230 kV network

The Exciters and Governors library contains more than 30 standard models for governors, exciters and power system stabilizers including various models from the IEEE Standard 421.5-2005 “IEEE Recommended Practice for Excitation System Models for Power System Models for Power System Stability Studies”.

Power electronics and FACTS (HVDC, SVC, VSC…)

For time-domain simulations, EMTP includes an iterative solver to solve system nonlinearities. This unique capability keeps an excellent simulation accuracy without requiring an unnecessary small time-step when simulating static converters. Furthermore, EMTP is based on the trapezoidal integration and uses an breakthrough technique to remove the inherent numerical oscillation of the trapezoidal integration. When a discontinuity occurs, the integration method is switched to Backward-Euler and the time-step is reduced to increase the precision. Therefore, numerical instabilities are very rarely encountered in EMTP.
Figure 8 presents the EMTP modelling of the CIGRE B4 DC Grid system. It is composed of loads, ac and dc cables, ac and dc overhead lines, ac grid, wind farms and VSC station based on the Modular Multilevel Converter (MMC) technology.

Figure 6: CIGRE B4 DC Grid (Source)

Large grids

EMTP is based on cutting edge technologies developed and validated by internationally recognized experts from the power system industry. The solver uses a matrix formulation, unique in the industry, for the load-flow, steady-state and time-domain solutions. An open-architecture graphical user interface (GUI) is available to maximize flexibility, and allow creating and maintaining very large and complex designs.

Figure 7: Example of a large grid modelled in EMTP: The French transmission network (200 substations, 380 lines, 45 generators with detailed controls, HVDC converters…).