HIFREQ - Electromagnetic Fields Analysis

Technical Highlights

HIFREQ calculates the scalar potential, and the electric and magnetic fields due to an energized conductor network, as well as the current distribution in the conductors. HIFREQ was designed to solve problems accurately, without ignoring soil characteristics, conductors in the soil, or nonenergized metallic structures in air or soil. With HIFREQ you can:

• Study transients (such as lightning, switching surges and any conceivable surge problem) and high frequency disturbances on power system networks, structures and grounding systems at frequencies ranging from a few hertz to hundreds of megahertz...
• Calculate current and potential distributions in all conductors, EMF values in air and soil and voltages along well defined paths due to buried or in-air power system conductors and structures.
• Calculate electromagnetic interference to pipelines, communication lines, etc.,in one single step. Inductive, capacitive and conductive effects are accounted for simultaneously!
• Analyze cathodic protection problems and optimize rectifier capacities and locations on protected structures extending up to hundreds of km.
• Use FFTSES, a fully integrated and automated Fourier Transform tool, to visualize electroma-gnetic fields in the time domain.
• Study re-radiation interference or calculate current distributions in monopole, quarter-wave, and other antenna structures excited at frequencies reaching hundreds of megahertz.
• Calculate induction between arbitrary circuits at low and high frequencies and during surge conditions. Determine self and mutual impedances as well as capacitances of these circuits regardless of whether they located above or below ground!

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.