Dangerous touch voltages in buildings: The impact of extraneous conductive parts in risk mitigation

Abstract

International (IEC) European (CENELEC) and American (NEC) Standards require, in each building, the connection of extraneous conductive parts (i.e. metal water or gas pipes) to the main grounding terminal. There are two good reasons for this: the voltage between extraneous conductive parts and exposed conductive parts is zeroed and extraneous conductive parts can contribute to the leakage of fault current into the ground. There is however a third advantage in the bonding connection: the entire structure (floors and walls of the building), together with the exposed and the extraneous metallic parts, forms a quasi-equipotential system, with the consequent strong reduction of touch voltages. Metallic pipes and reinforcement of reinforced

Improvement of safety of autonomous electrical installations by implementing a method for calculating the electrolytic grounding electrodes parameters

“…where ( 1 5 )where l is the scale of the spatial dimensionality, n is the number of structural elements (pores) in a cluster, k com.por is the filling factor of the electrolyte for a pore space, equal to (16): where V geom is the geometrical body volume, m 3 , V el is the electrolyte volume, m 3 ; k por is the coefficient of soil porosity. The number N can be determined from formula (17):…”

“…Existing PC of NRGD [3] consider soil structure as a pseudo-homogeneous structure with layered variations of large scale, or as a medium with parameters that change gradually in the specified direction. All the properties of the soil structure, predetermined by its heterogeneity, are expressed in calculation formulae by characteristic empirical coefficients whose magnitudes of values could be within a few orders of magnitude.…”

Electric Shock in Urban Village: Reflections from A Practical Accident

“…Equipotential bonding is essential for TN systems. If the enclosure of the equipment, the reinforcing bars of the building and other extraneous conductive parts are connected to the main grounding bus bar, a significant reduction of touch voltage can be achieved [7]. The building of concern is a brick…”

“…However, in practical cases, it is hard to implement. In [7], the authors use electromagnetic simulation to analyze the touch voltage in the building under different bonding conditions during ground faults. It shows that the presence of widespread metallic parts in buildings helps to reduce touch voltages, but not enough to ensure safety against indirect contacts.…”