Neutral resistive earthing in 6-35 kV distribution networks

The choice of neutral grounding mode in 6-35 kV networks is an important issue in the design, operation and reconstruction of electrical distribution networks, which determines the uninterrupted supply of consumers, the safety of personnel and electrical equipment during a single-phase earth fault (SPEF), and overvoltage in undamaged phases during SPEF, current at the place of damage during SPEF, the principle of building relay protection against earth faults, insulation level of electrical equipment, permissible ground loop resistance of the substation. The neutral grounding mode in 6-35 kV networks affects a significant number of technical solutions that are implemented in a particular network. The paper considers the problem of selecting the neutral grounding mode in distribution networks with a voltage of 6-35 kV. It is shown that the use of neutral grounding resistors in networks with a voltage of 6-35 kV can significantly improve the reliability of networks, reduce the accident rate during single-phase earth faults and automate the process of finding a damaged feeder. An example of calculating the resistance value of a resistor for an NPS substation is given. Experimentally, the model shows the effectiveness of using resistive neutral grounding at an NPS substation. It has been established that when changing the parameters of the power supply system when turning off or on new feeders in order to maintain the magnitude of the overvoltage ratio at an accepted or predetermined level, it is necessary to change the resistance value of the resistor by the value of the change in earth fault current.