The resistance of the Earth is non-zero, so current injected into the earth at the grounding electrode produces a potential rise with respect to a distant reference point. Short-circuit current flows through the plant structure and equipment and into the grounding electrode. 6 High-voltage protection of telecommunication circuitsĮarth Potential Rise (EPR) is caused by electrical faults that occur at electrical substations, power plants, or high-voltage transmission lines.This transferred potential is a hazard to people and equipment outside the substation. Any conducting object connected to the substation earth ground, such as telephone wires, rails, fences, or metallic piping, may also be energized at the ground potential in the substation. The change of voltage over distance (potential gradient) may be so high that a person could be injured due to the voltage developed between two feet, or between the ground on which the person is standing and a metal object. Ground potential rise is a concern in the design of electrical substations because the high potential may be a hazard to people or equipment. The potential relative to a distant point on the Earth is highest at the point where current enters the ground, and declines with distance from the source. In electrical engineering, earth potential rise (EPR) also called ground potential rise (GPR) occurs when a large current flows to earth through an earth grid impedance. Finally, the impacts of geotechnical and geometrical parameters on the earth pressure were discussed.Rise of voltage of local earth when a large current flows through an earth grid impedance The experimental and numerical results and Terzaghi’s solution were adopted to assess the validity of the proposed model, which indicates that the proposed model not only coincide with the test results of average vertical earth pressures on the tunnel, but also describe the nonuniform distribution characteristics of vertical stress on the circular tunnel, namely, the minimum vertical earth pressure is located at the centreline of the tunnel, and then gradually increases as it moves away from the centreline. The key parameters (i.e., width and height of friction arch zone, thickness of end-bearing arch zone and lateral stress ratio in friction arch zone) in the proposed model were suggested according to the existing literature, and a formula for predicting the height of the friction arch zone was deduced. The model is composed of three parts: the upper end-bearing arch, the stability zone and the lower friction arch. A multi-arch model for calculating the distribution of the vertical earth pressure on a deep tunnel in dry sand was then proposed based on the limit equilibrium method. In this study, the stress-transfer mechanisms of soils in different zones above the tunnel were analyzed firstly. It is of great significance for ensuring the lining safety to reasonably determine the earth pressure on the tunnel, especially the deep-buried tunnel.