大型中压电动机远距离差动保护的配置

Analysis of Long-distance Differential Protection for Large-capacity Medium Voltage Motor

为提高电动机的差动保护特性、防止差动保护误动作,以印尼公主港3×350MW燃煤电站为工程背景,分析了大型中压电动机差动保护中电流互感器的参数选择及保护装置配置。根据差动保护原理,通过比较电流互感器不同的准确限制系数、变比和差动保护装置至电动机的电缆距离的影响,得知为准确反映极大的故障电流、减小二次回路负载、保证电动机安全正常运行,电流互感器需选择小的额定二次电流,并且二次回路电缆长度应较短。工程实际也验证了这一点。

In the power plant,the motor with capacity more than 2000kW should be installed with the differential protection. In order to promote the property of the differential protection and prevent from misaction,and by employing the Indonesia Palabuhanratu 3×350MW coal fired power plant for background,the parametes of current transformer and protection device of long-distance differential protection for large-capacity medium voltage motor are analyzed. According to principles of the differential protection,through comparing accuracy limit factor,conversion ratio and cable distance from protection device to motor,it is found that choosing small rated secondary current,placing protection and current transformer beside the motor would convert fault current exactly and decrease the sencodary load for saft running,which is confirmd by the actual project.