Changing the operating mode of the 6 kV power supply system when switching from the isolated to the resistive-grounded neutral

The existing system of the electric network 6 kV used in the greenhouse facilities “Ovoshchi Krasnodarskogo kraya” with the insulated neutral does not ensure its reliable operation. Short single-phase short circuits in the network lead to ferroresonance, multiple short circuits and failure of power line sections and electrical equipment of the network up to the complete halting of greenhouse production. To eliminate ferroresonance processes and overvoltages in the electrical network and increase the reliability of the electrical supply system of the greenhouse facilities “Ovoshchi Krasnodarskogo kraya”, the authors have analyzed the effi ciency of an electrical supply system of 6kV network at its transition from the isolated neutral to the resistive-earthed neutral. They have determined the values of the capacitive currents of the electric network sections of the greenhouse facilities to show the excess of their allowable values. Based on the results obtained, they have stated the need for the modernization of the neutral grounding system of the electric network of the greenhouse facilities by transition to the neutral grounding through the low resistors used in commercially available transformer neutral grounding cabinets with the resistors 100 ohm for the 6 kV networks. The change in operating mode of the high-voltage network of the greenhouse enterprise from the isolated neutral to the resistive-grounded neutral ensured its reliable operation without interruptions of power supply and disconnection of its consumers. The network modernization has increased the current at the point of a single-phase short circuit to ground and provided the possibility of an immediate shut down of the damaged lines, thereby avoiding repeated short circuits in power lines and damage of electric equipment caused by ferroresonance. It has also reduced the probability of intermittent short-circuits, overvoltage in the network and electric shock to personnel and bystanders. 

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