Earthing aspects of transformer stations and towers

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Supervisor:
Dr. Ladányi József
Department of Electric Power Engineering

In order to operate the power system reliably and safely it is essential to have adequate earthing for substations and transmission line towers, which primarily means low resistance to earth. After presenting the definition, standards and specialized literature of the resistance to earth and its measurement, three main topic is discussed in the thesis. All of them is a computer simulation study.

The most common method for measuring the resistance to earth is the Fall-of-Potential method, which requires two auxiliary earth electrodes. If the auxiliary earth electrodes are not located to the appropriate distance, it might cause measurement error. A study has been carried out for this type of measurement error in case of a substation and a transmission line earthing grid. I started this topic in my bachelor thesis. The results presented here are about the case when the leads are at right angles.

In case of transmission line towers it is a common problem when the resistance to earth is higher then allowed. In order to assess the possibilities related to earthing improvement, a detailed computer simulation study has been carried out in case of backfill usage and connecting the transmission line towers above or in the ground.

Finally, a research was carried out about the measurement error of the inductive coupling between leads while measuring the resistance to earth via Fall-of-Potential method in case of a transmission line tower grid.

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