Influence problems of primary equipment of high voltage switchgear and natural electromagnetic phenomena on secondary equipment can be clasped with general notion like electromagnetic compatibility problems in switchgear of electricity system. The most important fact of that problem are fast and very fast overvoltages in secondary (low voltage) circuits. After introduction part, in second part were given fundamental definitions and classes according to IEC norms. In third part were presented overvoltage problems in low voltage circuits of high voltage switchgear. In this part were detail divided lightning influence and switching operation influence. Also, in this part were detail described transfer mechanisms between source of disturbance and receiver of disturbance by classic switchgear and by gas insulated switchgear. Concept of protection area in lightning protection, like measure of electromagnetic compatibility, was presented in fourth part. Application of that concept and necessity of interdisciplinary work of all members in project was also explained in this part. In fifth part were presented two computer programs for lightning stroke simulation. In this part was also given mathematics models, which were implemented in programs. Results were also compared on concrete switchgear. Results of simulations from preliminary part were used in sixth part like introduction data for calculation of transient potential rise of grounding grid. In this part was presented only a little piece of calculation, which were made. In seventh part were presented encircle protection measures. These were divided into measures against common-mode voltage and measures against line to ground voltage. In this part were presented, between others, protection element that can be used like addition protection measures on second side (in low voltage circuits). For certain of those elements were recorded responses on fast-front overvoltages. In conclusion were given the most important directions by building of new and reconstruction of existing high voltage switchgear. These directions are results of work on problems of fast-front overvoltages in secondary low voltage circuits.