- an important expansion of the underground net-work in rural environment. This leads to high phase-to-ground capacities of the outgoing feeders; which increases fault currents in networks using impedant grounding;
- an increased sensitivity of the customers to the quality of supply;
- changes in international standards (insulation coordination).
The introduction of arc suppression Petersen coils allows both to reduce the current in single phase-to-ground faults and to improve the quality of supply by reducing short supply disconnection.
Adapting this solution to the existing networks made it necessary to change the protection system; by using zero sequence wattmetric relays.
The feedbacks of the zero sequence wattmetric relays operating today show the need of an evolution of this protection equipment specifications. To address this need; EDF R&D has investigated the use of Modelica language for the electrical system modeling.
At first the relevance of Modelica language for electrical systems modeling has been studied. This work was made from a comparison of simulation results with those traditionally obtained with EMTP software; normally used by EDF R&D. This paper details this approach and underlines the interest of Modelica for the electrical network fields. The next step will be the use of the ModelicaML profile in order to establish a new version of the protection system specification.
 Spécification Technique EDF HN 45-S-54 Régime de neutre compensé - Spécification de la Protection Watt-métrique Homopolaire
 http://www.openmodelica.org/index.php/developer/tools/134 ModelicaML - a UML profile for Modelica
 http://www.emtp.com/ EMTP-RV - Computational Engine
 Principles of Object-Oriented Modeling and Simulation with Modelica 2.1 Peter Fritzson