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Effect of the let-through energy of overcurrent protective devices on the temperature of conductors during short-circuits

Czapp Stanisław, Kowalak Daniel

Przegląd Elektrotechniczny

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2021

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R. 97, nr 8

27--30

EN

The scope of the verification of low-voltage systems covers the earth fault loop impedance measurement. This measurement is usually performed with the use of low-value current meters, which force a current many times lower than the one occurring during a real short-circuit. Therefore, the international standard recommends consideration of the increase of resistance of conductors with the increase of temperature, which may occur during short-circuits. This paper analyses the temperature rise of the conductors during short-circuits, taking into account the let-through energy of protection devices. The analysis has shown that in typical circuits the temperature rise of conductors is not significant.

PL

W ramach kontroli stanu instalacji niskiego napięcia wykonuje się pomiar impedancji pętli zwarciowej wymuszając prąd znacznie mniejszy niż występujący podczas rzeczywistego zwarcia. Norma dotycząca sprawdzania instalacji niskiego napięcia zaleca, aby w przypadku pomiarów małym prądem, w temperaturze pokojowej, uwzględnić fakt, że podczas zwarcia temperatura i rezystancja przewodów może wzrosnąć, co zaostrza warunek skuteczności ochrony przeciwporażeniowej. W artykule przeanalizowano, w jakim stopniu może wzrosnąć temperatura przewodów podczas zwarć przy uwzględnieniu całki Joule’a wyłączania zabezpieczeń nadprądowych. Z analizy wynika, że wzrost ten jest niewielki.

2

Let-through energy of miniature circuit breaker in function of phase angle of short-circuit current

Książkiewicz A.

Poznan University of Technology Academic Journals. Electrical Engineering

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2014

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No. 78

59--64

EN

Let-through energy (Joule heat) is an important factor in proper protection of electrical installations and devices. Studies were preformed during which the relationship between amount of energy and phase angle of short-circuit current was examined. Typically used miniature circuit breaker was utilized as a protective device. Scilab software for numerical computation was used to calculate the let-through energy based on recorded oscillograms of short-circuit current. Results of this calculations are presented.

3

Joule’s heat generated during a short-circuit current flow in function of phase angle

Książkiewicz A.

Computer Applications in Electrical Engineering

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2014

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Vol. 12

162--170

EN

Joule's heat (let-through energy) is an important factor in proper protection of electrical installations and devices. Studies were preformed during which the relationship between amount of energy and phase angle of short-circuit current was examined. Typically used miniature circuit breaker was utilized as a protective device. Scilab software for numerical computation was used to calculate the let-through energy based on recorded oscillograms of short-circuit current. Results of this calculations are presented.