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This paper describes a new technology, the active earthing system, based on a multi-frequency power converter, which combines a new power electronic device with a protection and control system. This system allows network enhanced operation and maintenance, overcoming some of the limitations of the traditional earthing systems, giving rise to relevant improvement in supply continuity.

Abstract-The effect caused by ground fault current in a complex system of interacting electrodes is theoretically studied. The calculation applies to a specific case in which a set of interconnected electrodes, which are part of a grounding facility network, are activated by a ground fault current. Transferred potentials to adjacent passive electrodes are calculated and the most relevant parameters of the electrode system are evaluated. Finally, the convenience of connecting the grounding electrodes is discussed.Index Terms-Transferred potentials, grounding analysis, thin wire structures, earth fault, Method of Moments. I. INTRODUCTIONhe grounding systems (GS) are an essential part of the distribution networks of electrical power. Proper design of these systems prevents the occurrence of anomalous potential that can be dangerous to people and damage sensitive equipment and other neighboring facilities. The situations in which such a GS is indicated ranges from fault currents in electrical systems due to a malfunction, to an eventual lightning stroke. In any situation, the main target of a GS is to ensure that their electrical resistance is low enough to guarantee that fault currents dissipate mainly through the grounding grid into the earth, while maximum potential differences between close points on the earth's surface must be kept under certain tolerances (step, touch, and meshIn real GSs, we should take into account not only the conductors directly involved in the installation to be protected, but also any other conductor, connected to it or not, that can interact with the whole GS in case of activation [3]. The transfer of potentials between the grounding area and outer points by buried conductors, such as communication or signal circuits, neutral wires, pipes, rails, or metallic fences, may produce serious safety problems [4], [5]. It is also important to take into account the metal structures of the neighboring buildings of the protected area because there may appear transferred contact potentials out of the tolerance range [6], [7]. The ground potential rise (GPR) due to electrical current dissipation to the ground is a well known and studied phenomenon from the equations of electromagnetism [8]. However, in practical situations, many difficulties may appear which greatly complicate obtaining a solution. The shape of the electrodes and their spatial arrangement together with the possible interconnection of some of them, establish multiple boundary conditions added to the problem which can greatly complicate reaching an acceptable solution, which is obtained in most cases by applying numerical methods [9]-[12].In this paper, we consider a section of the electric power network of an urban area, where several Secondary Substations (SS) can be found together with their corresponding GS. In the case of study, the GSs of all the SS considered, are interconnected via the underground cable shield that transmits power to the SS. Besides ensuring an equal electric potential of all the interconnected GS electrodes, ...

A new kind of overvoltage, not covered by present standards, has been detected in solar plants when switching the inverters off. This power frequency overvoltage can be transmitted to the MV network, giving rise to damages to some pieces of low voltage electronic equipment. This phenomenon has been investigated in the field, testing several inverters in different solar plants, where the overvoltages, as well as the damages in revenue meters, have been reproduced and recorded. It has been proved that some inverter configurations are more prone to create severe overvoltages than other. In addition, some solutions have been tested and a laboratory test to reproduce the phenomenon is proposed.

A new kind of overvoltage, not covered by present standards, has been detected in solar plants when switching the inverters off. This power frequency overvoltage can be transmitted to the MV network, giving rise to damages to some pieces of low voltage electronic equipment. This phenomenon has been investigated in the field, testing several inverters in different solar plants, where the overvoltages, as well as the damages in revenue meters, have been reproduced and recorded. It has been proved that some inverter configurations are more prone to create severe overvoltages than other. In addition, some solutions have been tested.