影响电力系统运行的因素 Hazards to Power System Operation⑴The operation of electric power systems may be disturbed as the result of a number of causes. The troubles on the electric circuits are usually in the form of broken conductors or circumstances in which conductors are temporarily (or permanent) connected to each other or to ground. Regardless of the cause of the disturbances, such troubles seriously interfere with the flow of power and require corrective action.⑵Overhead lines are vulnerable to troubles caused by lightning. When lightning strikes a line or a nearby object, a transient voltage is created on the line ,Hihg-voltage circuits have large spacing between conductors and from conductors to grounded objects, such as towers. Direct strokes to such lines are usually diverted to ground through overhead ground wires and may cause no interference with operation. Occasionally strokes terminate directly on the power conductors and introduce onto them transient transient voltages of such magnitude that archer across insulator strings may result. Once an arc is established, power current flows through it until the circuit is deenergized . Lightning voltages may be of high magnitude but are of very short duration; their time is measured in microseconds. As a result, their effects are most noticeable at the point where the stroke occurs. Distribution lines, which operate at perhaps 12kV or less, are mounted on relatively small insulators, which may be flashed over by the voltage induced in a line even though the lightning stroke does not contact the line. Such resulting arcs interfere with operation and usually are eliminated by deenergizing the line. When the line is deenergized . The arc is ex...
