The main goal of this master thesis is to learn the process of measuring electric field strength and magnetic flux density of low-frequency electromagnetic field using Narda Safety Test Solutions set, which includes the EHP-50F field strength analyser and related equipment. The first chapter describes the basic concepts related to electromagnetic radiation, types and sources of radiation. The basic limitations and limit levels of reference values of electromagnetic fields, prescribed by national and international institutions are given, as well as areas of exposure to these fields. The second chapter of the thesis describes devices used to measure electric field strength and magnetic flux density (EHP-50F, Sypris 4090, Extech EMF450). The use of the EHP-50F field strength analyser and related equipment is elaborated in detail along with the main features and capabilities of the EHP-TS software used for time and frequency analysis in real-time. The third chapter of the master thesis presents the procedure for measuring the electric field strength and magnetic flux density in the 400 kV part of the substation TS 400/220/110 kV Konjsko. The measurements are shown by the exact positions on the model of the 400 kV part of the plant, the results in the tables corresponding to each position and the comments for each group of measurements. Finally, a comparison of the obtained measurement results with the measurement results from eleborat of the Croatian Transmission System Operator was made.