Anti-shock safety of industrial electric installations with built-in frequency converters

Refinement of the mathematical model of frequency converter cable branch with a single­phase short circuit

“…The inability to determine the impedance of the phaseto-ground short circuit at the FC output if the protective device is connected in the common part of the network complicates the construction of protection devices [7]. Erroneous operation of regular ground fault protection devices can also be caused by the semiconductor converter as a part of the mine section electrical network [8].…”

“…and the submatrix7 F is zero due to the disconnect between inductive edges and resistive chords.Based on Kirchhoff's laws, matrix equations are compiled to calculate the vectors of currents of resistive edges I Red and voltages of resistive chords U Rch :Taking into account Ohm's law for resistive edges and chords, the equation that enables to calculate the vector I R =[I Red I Rch ] T of the resistive elements currents is possible to obtain from (12):…”

Mathematical Modeling of Current Leakage in the Combined Power Network of a Mine

“…To protect against leakages, the low-voltage power networks of the mine are equipped with a protective device. However, a leakage current to the ground in the cable, that connects the motor to the FC, cannot be detected by such a device with satisfactory reliability [1]. This determines the relevance of the scientific and technical problem of increasing the electrical safety of underground combined power networks.…”

Improving the mathematical model of a three-phase autonomous voltage inverter

“…Для захисту від витоків струму на землю низьковольтні електромережі шахти обладнують апаратом захисту від витоків струму на землю (наприклад, АЗУР-4пп). Проте витік струму на землю в кабелі, що під'єднує двигун до ПЧ, не може бути з достатньою надійністю виявлений загальномережевим апаратом захисту [1]. Причина полягає у викривленні постійного оперативного струму, що накладається на мережу апаратом захисту з метою контролю опору ізоляції, напівпровідниковими елементами ПЧ [2].…”