HIFREQ - Analyse des champs électromagnétiques

Technical Highlights

HIFREQ peut être appliqué à des fréquences mesurant DC à une centaine de mégahertz. Il est particulièrement fait pour analyser de grand réseaux de conducteurs et les réseaux constitué de conducteurs entérrés et en surface.

HIFREQ vous offre les possibilités suivantes avec puissance et flexibilité.

• Le logiciel peut calculer automatiquement la distribution de courant se trouvant à l’intérieur des conducteurs selon une base de courant et de source de voltage pré-enregistrée. Par contre, vous pouvez spécifier explicitement d’autres courants.
• Vous pouvez rechercher les effets ou les différents phénomènes individuellement: Vous pouvez choisir, par exemple, d’ignorer les effets d’induction ou la perte de courant à la fin des conducteurs.
• Vous pouvez sélectionner une combinaison de méthodes de réseaux d’alimentation: Injection de courant, sources de voltage, energisation GPR (pour lequel un voltage est fixé à une valeur spécifique) et application extérieur de champs électrique.
• Vous pouvez modeler des paramètres ovales et des conducteurs recouverts.
• Analyse du problème d’induction causé par les lignes de transmission et l’effets de protection des structures métalliques entérrées ou non.
• Calcule du champs électromagnétique généré par le réseaux entérrés.
• Si le courant flottant dans et à l’extérieur de la station est connu, HIFREQ peut déterminer tout le courant flottant dans le réseaux de mise à la terre, dans les conducteurs neutre tout comme pour les courants flottant dans les structures nonenergisée, ceci permettant d’enregistrer les champs magnétiques dans la sous-station.

HIFREQ gives you the following powerful and flexible features.

• Choose to have the software calculate the current distribution in the conductors automatically based on a set of impressed currents or source voltages, or specify the currents in the conductors explicitly.
• Investigate the effects of different phenomena individually: you can choose, for example to ignore induction effects, or current leakage at the ends of conductors.
• Model horizontally layered soil structures.
• Select a combination of four network energization methods: current injections, voltage sources, GPR energizations (for which the voltage at a point is clamped at a specified value) and externally applied electric field.
• Model lumped parameters such as a resistor, inductor or capacitor within a conductor.
• Support bare and coated conductors.

FURTHER DETAILS

Voltage Energization

A new form of energization, called VOLTAGE, is now available. A conductor connected to a VOLTAGE energization represents a simple model for an AC voltage generator: the voltage increases along this conductor by an amount specified by the user. By connecting one end of this generator to the ground, the other end can be kept at the desired potential.

Lumped Impedances

The VOLTAGE energization only determines the voltage on the line. To define the current, one must specify the load on that line. This was usually done by specifying a conductor segment having specific resistivity and permeability values selected to yield the required internal impedance. It is now possible to do so by simply attaching a series combination of a resistance, an inductance and a capacitance to any given conductor. The program then computes the resulting load impedance at the energization frequency.

GPR Energization

The GPR energization has been improved. It can be used to force the scalar potential at the surface of a conductor (GPR) to be at a user specified value. The current flowing in the conductor is not determined and must be supplied with another ENERGIZATION (typically, a LEAD). This represents a shortcut over the VOLTAGE / load combination above but it is less physical and can lead to unexpected results if not used properly.

Of course, the use of the VOLTAGE and GPR energizations and of lumped impedances is not limited to the transmission line application discussed above. Many other applications are possible. In fact, it is possible to use these features in HIFREQ to do conventional circuit theory calculations!

Coating

In previous versions of HIFREQ, the only form of conductor insulation that was available was a "mathematical" insulation in the sense that no current was allowed to leak from the conductor. This is essentially correct for the computation of magnetic fields but yields incorrect results for the electric field and scalar potential. This restriction was eliminated by the introduction of physical (i.e. leaky) coatings. It is now possible to specify that a conductor be coated with a layer of a dielectric material of user-defined thickness, resistivity, permittivity, and permeability.

Applied-Field

The response of a conductor network to the presence of an externally applied uniform electric field can be very interesting, particularly to simulate the effects of distant lightning strikes or geomagnetic disturbances. HIFREQ can now carry out such a calculation. The user-supplied value of the constant applied electric field in the air is used to compute the applied electric field everywhere else and the current distribution in the network. The scattered fields caused by this circulation of current can be obtained.