N.P. Kochetkov, T.A. Rodygina
Izhevsk State Agricultural Academy, ul. Studencheskaya, 11, Izhevsk, 426000, Russian Federation
Abstract. One of the common causes of disruption of overhead lines (OL) with the voltage of 35 kV is a single phase-to-earth fault (SPEF), causing overvoltage of the undamaged phases of a network. An effective measure to reduce the overvoltage is the neutral grounding of the network via a high-resistance resistor. A mathematical model of a transient process of sustainable SPEF was developed with assumptions that the phase-to-phase capacitances of the line and the resistance of 35 kV windings of the power supply transformer 110/35/10 kV are equal to zero, operating and constructive parameters of the electric network over phases are symmetric, and the parameters of the transition process are determined by active and inductive resistances of wires of the line and capacitance conductivity of the line phases with respect to ground. On the basis of the obtained analytical expressions of the mathematical model it was investigated the voltage waveforms of lagging and leading phases for different points in time of SPEF of dead-end single-circuit 35 kV overhead lines with the length of 30 km, made from AS-70 cable; as well as it was evaluated the influence of the magnitude of the grounding resistor on the shape of the curve of the transient process of lagging phase voltage. The transient process of the voltage of the undamaged phases of the line with the resistive grounding of the neutral at the SPEF has an oscillatory nature. With a resistance of 1 kOhm grounding resistor, the maximum initial overvoltage peak (70 kV) in the undamaged lagging phase is observed for the angle of 60 degrees of SPEF, in the undamaged leading phase (69 kV) – for the angle of 120 degrees of SPEF; the duration of the overvoltage in the undamaged phase of the line for any value of the SPEF angle does not exceed 25 degrees. The change the value of the grounding resistor from 10 kOhm to 0.5 kOhm in the lagging phase of the line changes the value of the initial peak of overvoltage of the transition process from 73 kV to 65 kV; the duration of the transient process reduced 4 times (from 140 degrees to 35 degrees); and the duration of the overvoltage reduced 6 times (from 30 degrees to 5 degrees).
Keywords: networks with an isolated neutral, resistive neutral grounding; single phase-to-earth faults; transient process of a stable single phase-to-earth fault.
Author Details: N.P. Kochetkov, Cand. Sc. (Tech.), assoc. prof. (e-mail: Этот адрес электронной почты защищён от спам-ботов. У вас должен быть включен JavaScript для просмотра.); T.A. Rodygina, Cand. Sc. (Educ.), assoc. prof. (e-mail: Этот адрес электронной почты защищён от спам-ботов. У вас должен быть включен JavaScript для просмотра.).
For citation: Kochetkov N.P., Rodygina T.A. Single Phase-to-Earth Fault in the Network with a Resistive Neutral Grounding. Dostizheniya nauki i tekhniki APK. 2017. Vol. 31. No. 8. Pp. 62-67 (in Russ.).