Grounding systems are essential for the safe and reliable operation of electrical power systems. Grounding systems allow a proper connection from your system's neutral to global earth potential. During a single-phase fault, the fault current flows back to the neutral via the grounding system which is ideally as low ohmic as possible. This current causes a potential rise of your entire grounding system towards the global earth potential.
The relevant standards EN50522, IEEE81 and IEEE 80/81 define maximum values for the potential rise which depend on the maximum single-phase fault duration of a system. These standards also mention limitations of maximum allowed step and touch voltages in and around the substation. Single-phase faults can have harmful or even lethal consequences, e.g. for humans and animals, when the maximum allowed step and touch voltages are exceeded.
Ground ImpedanceShow more
Ground impedance is the quality of the connection between the grounding system and its surrounding soil. An increased value is an indication of deterioration. In the event of a fault, the fault current and the ground impedance lead to a so-called Ground or Earth Potential Rise (GPR, EPR).
Step and Touch Voltage TestsShow more
Step and Touch Voltage Tests
Step- and touch voltages are caused by potential differences in the substation or by being too close to the grounding system when a fault occurs on a power line or within the power system. The measurement verifies that no critical potential differences for the human body have occurred.
The electric soil resistivity test (SRT) is performed before the construction of a grounding system. The soil’s electric resistivity is required for designing a grounding grid that meets all safety and functional criteria. The Werner or Schlumberger method are most often used.
Ground grid continuity
The ground grid needs to be able to reliably conduct the full fault current. A resistance measurement with high current can be used to check the ampacity between different parts of the systems, like raisers, grounding points, etc. Improper construction work and deterioration can be detected with this method.