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Magnetic Field Shielding

Backgrund

Power frequency magnetic field emissions from electrical infrastructure have emerged as growing concerns for stakeholders including utility operators, customers, and electromagnetic research communities.

These concerns stem from two primary issues:

  • Potential health implications associated with prolonged exposure periods and
  • Electromagnetic challenges that can interfere with sensitive electronic equipment.​

Solution

At power frequencies (50Hz/60Hz), magnetic field mitigation implement two primary mechanisms: flux shunting, also called magnetic shielding, and eddy current cancellation.
High-permeability ferromagnetic materials redirect magnetic flux lines around protected regions, while conductive materials, like aluminum and copper, generate opposing magnetic fields through induced eddy currents. For power cable applications, both ferromagnetic and non-ferrous conductive materials provide effective shielding.
In Grøft Design®, the interactions of electromagnetic fields generated by power cables with metallic structures are stimulated by solving Maxwell’s equations with the Finite Element Method.

Compare magnetic shielding Figure 1: Analysis of the magnetic field of the cables lying directly in trench A), and within the shielding raceway B)

Se Assumptions and Limitations for more information.

For comprehensive technical details, please refer to:

  • COMSOL AB, “AC/DC Module User’s Guide,” COMSOL Multiphysics v. 5.2a, 2016.
  • CIGRE Working Group C4.204, “Mitigation Techniques of Power-frequency Magnetic Fields Originated from Electric Power Systems,” CIGRE Technical Brochure 373, 2009.
  • G. Bucea and H. Kent, “Shielding techniques to reduce magnetic fields associated with underground power cables - Case study from Sydney Australia,” CIGRE Paper 21-201, Paris CIGRE Session 1998.