Abstract
This paper presents a comparative analysis of different earthing designs’ performances, with particular interest on the use of earthing enhancing compound (EEC) for a selected earthing design of 500 kV transmission towers in a rocky soil, using the SESCAD tool of the Current distribution, electromagnetic field grounding and soil structure analysis (CDEGS) software. The simulation included the interpretation of soil profile and comparison between designs A, B and C, which are currently used for the 500 kV tower footing resistance (TFR) improvement. Results showed each design had reduced the TFR by 66%, 54.7% and 63.2% for the towers T42, T48 and T50, respectively. In some cases, further improvement of TFR is required, especially in the rocky area where the soil resistivity (SR) value is of more than 500 Ω⋅m. In this case, EEC was used in Design C, encasing both the vertical and horizontal electrodes, and it reduced the TFR further by 16% to 20%. The characteristics of the soil and earthing arrangement design play an important role in achieving a low TFR value, which is directly proportional to the backflashover occurrence and thus to the transmission line performance.
Highlights
Reducing the tower footing resistance (TFR) is the right option for increasing the performance of a transmission line
This paper presented an analysis of TFR for different earthing designs and arrangements, taking into account the deployment of enhancement compound (EEC)
The significant contribution of this work consists in the information, crucially required by the power utility, concerning the TFR values related to each design and the percentual improvement made by deploying
Summary
Reducing the tower footing resistance (TFR) is the right option for increasing the performance of a transmission line. TFR coupled with soil resistivity (SR) is known to have a significant influence on the possibility of failure of a transmission line system [1]. The result of a TFR change depends on several factors, including the earthing structure and soil resistivity among others [3,4,5,6,7]. The structure of the earthing system has a relationship to the configuration or the tower footing shape. Round steel and profiled bar earth electrodes are buried at the base of each footing before the concrete foundation is mounted [8,9]. Earth electrodes and the tower footing are buried together during installation.
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