Influence of earthing conductors on current reduction factor of a distribution cable laid in high resistivity soil

Abstract

Various types of system circuit faults are possible. The most common is the phase-earth fault. During this fault, currents flow through earthing grids as well as through the earth. These currents are the consequence of electromagnetic coupling of conductors and earthing grid potentials and can he presented by current reduction factor. When earhing conductors are laid together with cables, the current reduction factor is very difficult to define. In this paper a mathematical determination model of current reduction factor is presented for the cable and earthing conductors laid in the same trench. Influence of both electromagnetic characteristics and earthing conductor geometrical characteristics as well as influence of geophysical features on the current reduction factor is analyzed in this paper.

Ground Return Current Behaviour in High Voltage Alternating Current Insulated Cables

“…In this section a comparison between MCA and k-factor approaches found in technical literature [8][9][10][11][12][13][14][15][16][17][18][19] and international standards [20,21] is presented. Figure 13 shows a single-circuit solid-bonded UGC during a phase 1-to-screen 4 short circuit: it occurs at receiving-end.…”

“…When the aim is the computation of the rise of earth potential (ROEP) at substation sites there are several contributions in the literatures involving the k-factors [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. These contributions are generally based on solidly-bonded (SB) cables and are not applicable to cross-bonded cables.…”

The Neutral Conductor Voltage in a Mediumvoltage Network During a Ground Fault

“…The procedure for the calculation of the ground fault current in the case of a cable without a metal sheath and in the case of a cable with a metal sheath when a ground fault occurs in an MV/LV substation in which the metal cable sheaths are not connected to the grounding system of the substation, while they are connected at the other end, is the same as previously presented. It is important to note that in this case impedance Z uz represents the equivalent impedance of all the self and mutual impedances of the system elements connected to the grounding systems of the medium-voltage and low-voltage U slučaju uzemljenja metalnih plašteva kabela na oba kraja jedan dio struje zemljospoja teći će plaštem, dok će drugi dio teći elementima koji su vezani na uzemljivački sustav i relevantni su za potencijal nul-vodiča [3], [4] i [5].…”

“…U slučaju kabelske mreže srednjeg napona utjecaj uzemljivačkih užadi kabela spojenih na uzemljivački sustav promatrane TS SN/NN uzima se u skladu s njihovim elektromagnetskim spregama s ostalim vodičima i pripadnim odvodima [3], [4], [5], [6], [7], [8] i [9].…”

“…In the case of metal cable sheaths grounded at both ends, one part of the ground fault current will flow through the sheath while the other part will flow through the elements that are connected to the grounding system and relevant for the neutral conductor potential [3], [4] and [5].…”