Current distribution in LV networks during 1-phase MV short-circuit

Tommasini

et al. 2015

1 --Global Earthing Systems (GESs), created by the interconnection of local Earthing Systems (ESs), should guarantee the absence of dangerous touch voltages. According to international Standards, one of the reasons for this safety characteristic of GESs is that MV and LV grounding systems form a quasi-equipotential area.Typical examples of GESs are in city centers, thanks to the high number of interconnected grounding systems in the area. For this reason, in addition to ground-grids, also other metallic parts with different primary functions shall be considered: for example, water and gas pipes, tramway tracks and building foundations can modify the electric potential distribution in the area.In this paper, a model based on the Maxwell's sub-areas method (MaSM) is used to evaluate how buried metallic parts, not intentionally connected to ground-grids, modify the electric potential on the soil surface.Firstly, the MaSM model is validated with experimental measurements on a simple electrodes configuration. The measured voltages are compared with the MaSM results and with the results obtained with a FEM model simulated with COMSOL Multiphysics.Then the simulations are carried out on a realistic urban test case.

Section: B Simulation Resultsmentioning

confidence: 99%

Global Earthing System: Can Buried Metallic Structures Significantly Modify the Ground Potential Profile?

Tommasini

et al. 2015

“…The neutral point of the MV distribution systems is isolated from ground or earthed through the so called Petersen coil for SLGF current reduction (resonant earthing). For this reason the fault can last for a certain time before being cleared [12].…”

Section: Single Line To Ground Fault In Hv/mv Systemsmentioning

confidence: 99%

Currents Distribution During a Fault in an MV Network: Methods and Measurements

Napoli

et al. 2016

When a single line to ground fault happens on the MV side of a HV/MV system, only a small portion of the fault current is injected into the ground by the ground-grid of the faulty substation. In fact the fault current is distributed between grounding electrodes and MV cables sheaths. In systems with isolated neutral or with resonant earthing this may be sufficient to provide safety from electric shock. Experimental measurements were performed on a real MV distribution network: a real single line to ground fault was made and fault currents were measured in the faulty substation and in four neighboring substations. In this paper the problem of fault current distribution is introduced, the test system is described and the measurements results are presented.

“…The neutral point of the MV distribution systems is isolated from ground or earthed through the so called "Petersen coil" for SLGF current reduction (resonant earthing). For these reasons the fault can last for a certain time before being cleared [18].…”

Section: Structure Of MV Distribution Systemsmentioning

confidence: 99%

Impact of MV Ground Fault Current Distribution on Global Earthing Systems

Napoli

et al. 2015

Global Earthing Systems (GES), created by the interconnection of local earthing systems, should guarantee the absence of dangerous touch voltages. One of the reasons for this safety characteristic of GES is the fault current distribution between grounding electrodes and MV cables sheaths: only a small portion of the fault current is injected into the ground by the ground-grid of the faulty substation. In systems with isolated neutral or with resonant earthing this effect may be sufficient to provide safety from electric shock. In this paper a model describing the behavior of the MV distribution system with interconnected grounding electrodes during a ground fault is built. It is then used to analyze the impact of different factors on the fault current distribution. A sensitivity analysis is performed varying the main parameters and the results are used to draw some conclusions on the current distribution influence on global earthing systems.