## 1 Introduction to Electromagnetic Compatibility  
Electrical equipment and systems process electrical energy and share the space of the electromagnetic environment by interacting with each other. These interactions are often undesirable. Such phenomena are called \"electromagnetic disturbance\" and designate any electromagnetic phenomenon which may degrade the performance of equipment. Electromagnetic disturbance may be electromagnetic noise, an unwanted signal or a change in the propagation medium itself. The problems of limiting disturbance emissions and designing devices with a good level of immunity to them are defined by electromagnetic compatibility. Electromagnetic compatibility (EMC) means the ability of equipment to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to other equipment in that environment [1; 2; 3; 4]. Compliance with the requirements of electromagnetic compatibility by every electric device brings profits in terms of safety of their use. It is also a necessary legal condition to prove compliance with the requirements of European Union directives (e.g., [1]). Assessment of compliance with the requirements of the EMC Directive [1] is performed as technical tests of the equipment, which are given in harmonised standards. A positive assessment gives a presumption of conformity with essential requirements. The technical tests are intended to show whether the electrical equipment is not a source of hazardous electromagnetic disturbance and whether it is immune to electromagnetic disturbance in the environment. These interactions are shown in Figure 1. Objects A and B are real devices that work in some environment. When measuring the compatibility of object A, a system of measuring and testing equipment is introduced instead of object B. This system is compliant with the CISPR 16 series of international standards. The maximum levels of disturbance emitted by the equipment are strictly defined in the standards for that equipment by the value of the electromagnetic field strength in the environment of the object. The standards describe electromagnetic environments and their division into: (a) residential, commercial, light industrial and (b) industrial environment [1,2]. In order to verify the electromagnetic compatibility of the plasma reactor installation it is necessary to carry out tests in accordance with the regulations of the EMC Directive and harmonised standards. Disturbances from any plasma oscillating source including fluorescent lamps, discharge tubes, and plasma tubes used in radar modules, as well as electron beam and arc welding can affect the electromagnetic environment [5, 6, 7, 8, 9, 10, 11]. Internal electromagnetic disturbances as well as near and far field components are derived and plotted [12]. Studies on plasma-related electromagnetic emissions and arc discharge are carried out in many aspects of physics and human interactions [13,14]. According to the author, the plasma reactor power supply system, the working and ignition path, the discharge chamber, the gas feed system, together with the controls, are an example of a stationary installation that should be tested with a view to ensuring its proper functioning on the European market. According to the Directive [1], a fixed installation means a particular combination of several types of equipment and, where applicable, other devices, which are assembled, installed and intended to be used permanently at a predefined location. Therefore, the measurements of the plasma reactor installation were made at the place of its fixed installation, i.e., in the laboratory of the Department of Electrical Engineering and Electrotechnologies. The presentation of the full compatibility analysis of the installation makes for an extensive publication, therefore the article only deals with the analysis of electromagnetic emissions.