A new approach to monitor the integrity of grounding grids

Chikarov, Yury
Lie, Tek Tjing
Nair, Nirmal-Kumar C
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Doctor of Philosophy
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Auckland University of Technology

Connection of the potentially hazardous conducting parts of electric power plants with ground is the cheapest and most reliable way of providing safe conditions for staff and equipment of the power plant. The performance of the grounding mostly depends on the soil structure and its characteristics such as temperature, salts and acids presence, dampness etc. A grounding grid is buried in soil surface so that a visual inspection of its condition is difficult.

One of the main goals for grounding is to provide a continuous path for currents that may otherwise present hazard to the staff and equipment by dissipating the energy to the soil. For some cases it is to provide equipotential distribution throughout the territory of the power plant (substation). Both criteria can be met by only physically integrated grounding device. In situations of damaged grounding, safety parameters may be breached which may potentially result in electrocution of the staff and failure of the equipment.

Nowadays standardized and scientific techniques allow us to investigate a wide range of the grounding devices’ characteristics but unfortunately it is not enough for a comprehensive representation. Using technical data, it is only possible to estimate an area where damaged elements can potentially be. But they do not provide the information about exact location of the damaged element and its’ failure.

The proposed study sets up electric characteristics and features of the processes in grounding for different regimes. One of the parts of the analysis is dedicated to the determination and description of the processes with respect to a single horizontal element of the grounding grid. It then describes the features of the current and magnetic field distribution for the integrated and damaged horizontal element of the grid. A novel frequency response part of the analysis has also been carried out in order to establish a future investigative method using frequency of a test signal. The final part combines the parameters of the horizontal and vertical elements and their mutual coupling for the purpose of safety parameters evaluation. This part also describes distinctive features of the current and potential distribution in case of presence of the damaged horizontal elements. It includes not only mathematical but also a computer modelling of the processes. The exploration is intended to establish comparative performance of grounding with and without damaged horizontal elements.

The experimental part of the work validates and justifies the aforedescribed mathematical theory and formulation. It is also aimed at determination of the most appropriate parameters of the test signal for monitoring the health of the grounding devices.

This work also suggests a technical solution in terms of sequence of steps for the grounding devices’ investigation and a device which is capable of location of the dam-aged elements and position of failure.

Overall, this research is focused on creation of a new approach towards establishing condition monitoring of grounding integrity. Considerable benefits such as time and labor reduction for the grounding devices investigation with increase of accuracy of failures location can be achieved by using this proposed technique.

Grounding , Safety
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