Development of a Method for Identifying a Damaged Line During Ground Faults

Today, the electric power industry occupies a key position in the country's economy. In the age of digitalization, it is impossible to imagine any working system without electricity. Due to the growing dependence of all spheres of human activity on electricity, the requirements for quality and reliability of electrical energy are also growing. Today, the problem associated with ground faults (GF) in 6-35 kV distribution electrical networks remains unresolved. In Kazakhstan, they are the most common networks, in terms of line length, they account for about 70% of the entire existing line, i.e. about 341.3 thousand km. These networks are implemented with an isolated neutral configuration and resistive grounding (with high or low impedance grounding) and with compensated or combined neutral grounding. Analysis of operational data on electrical installation faults in 6-35 kV networks showed that most of these events occurred due to damage to phase insulation and because of ground faults, whose share is about 70-80% of the total number of faults. The ground faults are accompanied by possible damage to electrical equipment due to the overvoltages. During the operation of the 6-35 kV network, it is important to detect ground faults, since this mode occurs at low currents, commensurate with the operating current or even less, but with overvoltages. Overvoltages can lead to the phase insulation damage of other normal phases and to two phase-to-ground faults. Under short-circuit conditions, the protection relay operates and several lines are isolated, which reduces the reliability of power supply to consumers and overall efficiency of the distribution electric network. Existing methods for identifying ground fault locations do not provide the required selectivity. Low sensitivity of overvoltage protection is possible if GF occurs through the transient resistance. In combination, the existing methods reduce the efficiency of the electric network during ground faults. The paper proposes detection method for ground faults that is highly selective and sensitive to low currents due to the transient resistance. The proposed protection operates and isolates only the faulty line, due to its selective operation and eliminates the long-term impact of high over voltages on electrical installations, which is important during operation of an electrical network with the isolated neutral.