Magnetic field plots : new features

We introduced several new features for visualization of magnetic fields.

Posted 2022-04-01
Categories: New feature

The calculation of magnetic fields (EMF) plots for buried cables has been a feature in Cableizer from early on after introduction in 2016. The output were two subplots, one in 2D and one in 1D. The 2D plot shows a colormesh with isolines of the magnetic flux density calculated at any point around the cable installation and the 1D plot shows the magnetic flux density at various heights above ground. The calculation had to be done after the ampacity calculation with the given phase arrangements and current values. It was possible to set a specific phase shift between the systems, something which is only relevant for installations with different frequencies such as 50 Hz 3-phase systems and 16.7 Hz 2-phase railway systems used by some European railways.

In 2020 and 2021, we introduced step-by-step EMF plots as well for cables subsea, in tunnels, in troughs and in risers (considering cable going straight up). All these produced only a 2D plot. In addition, we introduced the possibility to include the EMF plot into the ampacity reports. The phase shifting setting was moved from the project editor to the ampacity result modal in order to simplify the setting in the editor and allow for more flexibility when testing phase shifting effects. Last but not least, end of 2021, the resolution of the EMF plot was increased a lot to allow for better usability of the downloaded png image.

With the new version from March 2022, many new features for visualization of magnetic fields (EMF) have been introduced which do increase the usability and improve the user experience.

  • Adjust the current value for each system when creating EMF after the calculation.
  • Define left and right width from $x=0$ axis.
  • Choose from 20 different Matplotlib colormaps plus optionally reverse them. The colormap we used so far is RdYlBu_r.
  • Select full-colored colormesh with black isolines or show only colored isolines on a white background.
  • Select 2D or 1D calculation separately for all installations (not applicable for riser).
  • Show the left/right extension of the magnetic field for a specific limit value which is a requirement in some countries (e.g. Switzerland).
  • New "zoom" button to calculate the magnetic field in the center area where the cables are. This used to be an image which appeared when hovering over the plot.
EMF in 2D, colormap RdYlBu_rEMF in 2D, colormap GnBuEMF in 2D, colored isolines
EMF in classic design with boundaries
EMF with colormap GnBu
EMF with colored isolines

Following limitations apply:

  • No calculation is possible in case of multiple parallel systems inside the same duct/pipe (reason is we cannot simply determine the location of the phases)
  • Gas insulated lines (GIL) and air-pressure cables (PAC) are not considered.
  • The twisting of phases greatly decreases the magnetic fields. This effect is not considered.
  • The induced currents in screen wires, sheath and ferromagnetic armour has a compensational effect which is not considered.

We plan to introduce further improvements for EMF. Our most challenging goal is the implementation of an optimization routine for the phase arrangement which has now to be set in the project editor before starting the ampacity calculation.