Problems Concerned with Single-Phase Ground Faults in Isolated Neutral Networks

Abstract

Matters concerned with normal operation of high-voltage isolated neutral power lines for longitudinal power supply of railways are considered. In railways, the signaling, centralization and blocking (SCB) system takes power supply from 6—10 kV high-voltage overhead power lines. Since uninterruptible power supply to the signaling system is required, the power lines are made according to the isolated neutral circuit scheme. A single-phase ground fault in such system does not lead to disconnection of the entire line, and a certain interval of time for locating and removing the fault is available. However, long-term operation of the overhead line supplying power to the railway SCB system with a ground fault in one phase is not admissible. A similar fault in another phase at any point of the network leads to a two-phase short-circuit ground fault, which leads to a serious emergency involving loss of power supply to the SCB system equipment. The technique of determining the distance to the single-phase ground fault is the most rapid and promising fault detection method.