Measurements carried out on the interconnected grounding systems of the three main substations of Brazil's Itaipu generating complex are described. These include ground mat resistances, ground impedances seen from each substation, ground potential rise, and mesh potential. The small magnitude of these ground system parameters as well as the interconnection between several nearby ground mats through the ground-wires of the 500 kV and 220 kV lines suggested the utilization of the measurement procedures introduced by A. Eleck (1962), modified for use with aluminium-cable steel-reinforced (ACSR) ground wires. The measured values showed good agreement with previously computed values. The procedures can be used to carry out grounding measurements at a single substation or to carry out simultaneous grounding measurements at two or more nearby substations, as reported here. It is shown that drastic reduction of the mat current and ground potentials is obtained by the utilization of ACSR ground-wires on some line spans near the substations, allowing the utilization of a ground mat conductor spacing several times bigger than if steel ground-wires had been used.
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