Analysis of the neutral conductor current in a three-phase supplied network with nonlinear single-phase loads

Abstract

This paper describes. what factors (i.e., load and supply) have an important effect on the neutral conductor current. It is shown that an asymmetry up to 10degrees or an unbalance of 10% in the power supply has only a minor effect on the rms value of the neutral conductor current. An unbalance in load conditions increases the neutral conductor current. Harmonics in the power supply voltage highly affect the rms value of the neutral conductor current

Pérdidas Joule en alimentadores que transportan corrientes armónicas en baja tensión

“…En un circuito simétrico y balanceado, la relación entre la corriente de neutro y la de fase se incrementa con el aumento del armónico de tercer orden y con la disminución del primero y quinto de la corriente de fase, según se demuestra en [6], donde se define: …”

“…El Alternative Transients Program (ATP) fue utilizado para simular condiciones de cargas con distintos niveles de distorsión. A partir de los resultados de las simulaciones, distintas fórmulas propuestas en la literatura [1,[5][6][7] fueron utilizadas para la estimación de la corriente de neutro y el cálculo de las pérdidas Joule en relación con las mínimas pérdida de potencia en la línea, para el mismo valor de potencia activa transmitida.…”

On the reduction of the third-order harmonic losses in low–voltage power cables used for feeding large LED and CFL lighting loads

“…As nonlinear loads, LEDs might produce highly-distorted currents. These distorted currents are injected into the power system thus producing a large number of problems, such as additional power losses in conductors, which are dependent on the harmonic frequency [9][10][11].…”

“…In four-core cables (three phases and neutral) the current in the neutral conductor may be larger than the current in the phase conductors when significant third-order harmonic currents are present [4,9,10]. This fact may lead to overheating of the neutral conductor unless the neutral is properly sized.…”

Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads

“…As nonlinear loads, LEDs might produce highly-distorted currents. These distorted currents are injected into the power system thus producing a large number of problems, such as additional power losses in conductors, which are dependent on the harmonic frequency [5]. The magnetic field generated by harmonic currents flowing in the conductor induces on the conductor itself eddy currents, which modify the current distribution displacing it toward the periphery; this "skin effect" phenomenon increases the value of the resistance (as compared to the dc resistance) in proportion to the root of the harmonic frequency, thus increasing the conductor power losses [6,7].…”