Substation Measurements

High Voltage Standard SFS 6001 requires the monitoring of grounding systems throughout their operational lifetime. We conduct grounding impedance measurements ranging from extensive interconnected grounding systems to individual grounding electrodes. Our toolkit includes the frequency-selective V/A method for determining total grounding impedance in large-scale systems, typically using 20-400kV overhead conductors and field cables as measurement leads. For narrower grounding systems, we employ the method of turning point measurements with various current supply cable lengths, as well as the V/A method. Our turnkey measurement report includes an assessment of compliance with relevant standards and regulations, as well as calculations and evaluations of touch voltages.

Electrical safety regulations require that the performance of grounding systems be adequate to ensure that no dangerous or disruptive voltages occur in the event of a fault in the electrical system. We perform touch voltage measurements and evaluations, as well as measurements of voltage spread using a frequency-selective method. Measurements can also be conducted in conjunction with grounding impedance measurements using the same measurement lead setups. If needed, we also measure touch voltages caused by the actual earth fault currents in distribution network testing scenarios.

We conduct soil resistivity measurements, also known as specific resistance measurements, in the field. The results of these measurements are used as input data for grounding design. Our experienced technicians are skilled in noting relevant factors for site planning during the measurements. Additionally, we can provide maintenance or geospatial data as needed during the same measurement visit.

The continuity of grounding systems in high-voltage installations must be checked at regular intervals. The connections in the grounding system must ensure good electrical conductivity to prevent excessive temperature rise due to fault currents. For groundings implemented with a single conductor, measurements are recommended every 6 years. For grounding systems with dual conductors, the recommended interval is 12 years.

We measure the continuity of grounding and potential equalization systems using both DC and AC currents. Typically, we conduct measurements with a minimum of 100 A DC current, but our equipment can handle higher currents if needed, for instance, to identify weak points

We measure the continuity between different grounding systems, such as within distribution networks, using transmission networks as measurement leads. We can perform necessary calculations and definitions based on measurement results, including the specification of a large interconnected grounding system in accordance with the SFS 6001 standard. Substation measurements play a crucial role in this process.

We measure the actual positive, negative, and zero sequence impedances of underground or overhead cable routes for protection calculations and settings – a common requirement might be for a 110 kV underground cable route with follow-up grounding and corresponding substations. We also measure reduction factors of lightning and other galvanically conductive routes and conductors, providing calculation services for these as well. Additionally, we measure and calculate voltages induced by various inductive, capacitive, and conductive couplings.