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Computational Electromagnetics – simulating the harmful effects of electromagnetic fields

Author Kari Haimi
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The 2004/40/EC European Union Directive governs the minimum health and safety requirements with regards workers’ exposure to electromagnetic fields. Overexposure to electromagnetic fields can have detrimental health effects and employers, as such, are responsible for taking preventative measures to protect workers in this regard. With the help of computational electromagnetics the exact interaction between electromagnetic fields and physical objects and the environment can be established. Making use of this technology not only ensures the health of workers, but can also reduce costs in the process.

Electric fields are caused by voltage differences and therefore powerful electric fields are often found in close proximity to high current power lines. Powerful magnetic fields, on the other hand, commonly occur near industrial transformers, welding devices or induction heaters.

According to the directive any electromagnetic field in excess of 500 micro Teslas (at 50Hz frequency) is a health risk. This is due to the fact that high voltage lines induce an electrical charge inside the human body while low frequency (below 50Hz) time-varying magnetic fields induce internal electromagnetic fields and circular currents. This can lead to internal warming of the body and result in several debilitating symptoms. High frequency dryers that use microwaves can cause warming on the body surface. Lower frequency waves penetrate deeper into the skin and cause more damage than higher frequency waves.

Employees with pacemakers are particularly vulnerable to electromagnetic radiation and should not be exposed to electromagnetic fields in excess of 100 micro Teslas. Low frequency magnetic fields are also known to interfere with the functioning of pacemakers and my lead to pacemaker malfunction.

It is worth noting that many apartment buildings are located near high power transmission lines, while workstations are sometimes also placed in close proximity to high power transformers. Humans that use those spaces are potentially placed at risk of overexposure to electromagnetic fields.

Overexposure can cause headaches, nausea, depression, hyperactivity and skin redness to name a few of the most common symptoms.

Employing shields to reduce exposure

The magnetic field caused by a transformer decreases considerably the further away one is from the transformer in question. When a human is close enough to the source of the electromagnetic radiation shields need to be employed to reduce the exposure to acceptable levels.

A common misconception is that concrete walls provide sufficient shielding, but this is simply not the case. In order to effectively reduce exposure levels, lead plates and grounded steel nets have to be employed. The dimensioning, positioning and material composition of shields have clear cost implications and this is where technical analysis tools come in handy to find optimal solutions.

Computational electromagnetics simulates exposure levels

Computational electromagnetics can be used to simulate the effects of electromagnetic fields and the effectiveness of shielding devices. It allows designers to define the optimal shield thickness, positioning and materials used by testing, for example, how transformers in different positions affect the surrounding environment.

The simulation provides the designer with a clear view of no-go areas for employees. This ensures that the shields employed are optimally proportioned not to take up unnecessary space, but sufficient to maintain exposure at safe levels.

In order for the simulation to be run the average power load and technical data of the transformer is required as well as the building dimensions and the materials that the transformer and building are made of.

simulation provides the designer with a clear view of no-go areas for employees

Typical simulation takes a few days

The analysis can be conducted, for example, with the ANSYS Maxwell software package. The modelling for a typical site usually takes a few days depending on the size of the site, the number of transformers and how close together or far apart they are. The scope of the study naturally also affects the time required; are magnetic fields or electrical fields being studied or both, and are the shield positions and dimensions also covered etc?

The information gathered during simulation can be used by employers to remove or reduce health risks effectively and reduce costs by ensuring optimized installations.

A safer working environment and one that complies with the applicable EU directive reduces sick leave, work accidents and other harmful effects. The result is a win-win situation both for employer and employee.

Link to EU directive:

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2004:184:0001:0009:EN:PDF

The original text was published in our 1/2014 Top Engineer magazine

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Kari Haimi

M.Sc. (Electrical Engineering) Kari Haimi graduated as a graduate engineer from the Tampere University of Technology in 2013. He started working at Elomatic in 2012. His expertise area is technical analysis and he has particular know-how in the technical analysis of electromagnetic fields.

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