- earthing measurements
- earthing grid designs for high and medium voltage substations
- evaluation of grounding studies, inspections of installations
All above are performed by skilled engineers, with the use of suitable measuring equipment and software packages
- Soil resistivity measurements (Wenner Method)
Basic measurement to categorize the soil in regard to its’ electrical characteristics in order to determine the suitability for the erection of a substation and to prepare an earthing study
- Ground impedance measurements in High, Medium Voltage substations, buildings etc
Measurement of ground impedance using all methods depending on the grids’ dimension, the surrounding area etc. Methods of measurements according to international standards are the following
- Fall of potential method
- 62% rule
- Three poles measurement
- Two poles and a clamp measurement
- Two clamps measurements
- Step, Touch Voltage, Metal to Metal measurements
Before initial energization of a high voltage substation or during maintenance period, voltage measurements are performed in order to determine the danger for humans within a substation in case of a short circuit fault or an accidental lightning stroke. Also step and touch measurement are contacting in the neighboring area of the substation.
Before conducting the measurements the following must be known
- substations’ soil resistivity value
- maximum short circuit current expected value
During these tests firstly a suitable current route is establishing between the earthing grid under test (E) and an auxiliary remote grid (R). Then current flows in the remote earthing grid, and simultaneously voltage measurements are performed in the grid under test.
After the test, measurements are stored, proportional voltages are calculated (in proportion to maximum short circuit current) and compared with voltage limits. Then a complete report is conducted with the final results.
- Loop continuity test
The loop continuity test includes the consumer's line conductor, the consumer's protective conductor, and the earth parth external to the consumer's installation (including the low-voltage winding of the transformer, the distribution line conductors to the installation, and the earth return path. The purpose of this test is to measure the actual value of the earth-fault loop impedance and to confirm that its value complies with the tabulated maximum values according to standards.
- Earth Systems Design
To ensure an earthing system will be adequate for the protection of personnel, plant and the public it must be well designed from the beginning, to ensure all possible scenarios are considered and allowed for. ATE uses the powerful earthing and grounding system software CDEGS™ to allow new earthing systems to be fully designed and modelled for performance.
Design of an earthing system is with strict adherence to relevant International Standards. By following the requirements and guidelines of these documents it is possible to create an earthing system offering the highest degree of safety, by reducing earthing system impedance to the general mass of earth, limiting Earth Potential Rise (also know as Earth Grid Voltage Rise) and minimising Step and Touch Potentials in the area.
A proper earthing design and earth testing regime is essential to ensuring the safety of personnel, plant and the public in the event of a power system fault. There are many conditions under which a power system fault can impress a voltage upon an earthing system with the two most common being through lightning strikes (causing flashover or diverted to earth through surge arrestors) and live conductors inadvertently contacting earth. When this occurs, the resultant current gives rise to an increase in the earth potential in the immediate area around the fault. Having an earthing system that is adequately designed and properly maintained will offer protection to personnel, plant and the public by limiting the voltage rise and directing the current flow into the general mass of earth. An earthing system that directs current flow into the general mass of earth with little resistance or impedance also allows for correct operation of protection devices ensuring any faults are cleared in the minimum time possible offering maximum safety and ensuring power system stability.
- Evaluation of grounding studies, inspections of installations
ATE’s engineers also perform evaluations of grounding studies and inspections of the complete installation in accordance with Greek and International Standards, rules and regulations.