In this thesis, electromagnetic radiation was studied using a power transformer as an example. This radiation is present every day, but people do not always notice it. It can be divided in groups according to the electromagnetic spectrum, where each group has its own useful applications. The most important part of the spectrum is the one that includes extremely low frequencies, because humans are mostly exposed to fields of such frequencies, either at the workplace or in their home. Sources of such radiation can be electrical devices, as well as various facilities such as substations, power lines and transformers. With the development of technology, there is an increase in the number of electrical devices and increased demands for electricity itself, due to which the human body is exposed to an additional amount of electromagnetic radiation. The electromagnetic field itself is a combination of two fields, electric and magnetic. The force created by the electric field over time is quite constant with certain rises and falls because it depends on the effective value of the voltage in the rigid network which is also quite constant. On the other hand, the magnetic field depends on the current. In this thesis, only the strength of the electric field of power transformer is measured in order to see whether it has harmful effects, or whether human health is threatened in any way if it is located near the transformer. In order for this measurement to make sense, it was necessary to specify the possible harmful consequences of exposure to electric fields of extremely low frequencies. The measurement itself is carried out using special methods that require the use of certain measuring instruments. In this case, a spectrum analyzer is used which, connected to a laptop, displays the measurement results both graphically and tabularly. Based on the obtained results and the permitted limit values previously mentioned in the paper, it is possible to make a conclusion as to whether the produced electric field is harmful or not.