Aspects on grounding

Modern electronic appliances receive signals from difierent sources like electricity, cable television, communication systems etc.. Their vulnerability for disturbances requires a well-designed grounding concept. In the ideal situation all grounding systems should be integrated in a so-called global earthing system. This grounding system must secure safety for both people and apparatus. In early days a reasonable earthing was obtained by metal objects like copper water tubes, gas pipes and sheets of PILC cables. Nowadays the water and gas tubes are made of plastic whilst power and telecommunication cables more and more contain plastic isolation. Local earthing of apparatus or total installations of a customer is not su‐cient in many cases. In order to obtain a proper grounding the grounding systems of electricity suppliers and customers should be interconnected. This is only allowed when faults in the electricity systems will not result in dangerous situations for the customer. Possible dangerous situations do not only occur due to faults in the low voltage system, but also due to faults in high and medium voltage systems. The consequences of these faults have been studied and verifled by measurements and fleld tests. This article describes the possible dangers and some countermeasures that can be taken. The flrst part contains (partly well known) information about grounding systems in electricity networks. The second part is dedicated to consequences of faults. The subjects in the article are related to typical power supply networks, which consist of underground cables for low and medium voltage and a combination of cable and overhead lines for high voltage.