【摘要】 该文介绍了并联型多端直流输电保护系统分区、测点和开关刀闸位置以及系统运行的方式。对于多端直流输电系统,直流线路保护设置保护线路全长时,可能发生区外故障误动;换流站线路保护需根据所连接的直流线路数目分别配置。在变电站,每条直流线路会配备一套保护装置,每套保护装置配置多套定值,其保护范围分别覆盖不同长度的线路;这些定值需根据其他换流站的运行情况进行切换;支线路故障后可采取隔离故障线路的处理策略,同时需闭锁隔离出来的换流站。不能通过检测是否存在流经接地站的接地电流,来判断是否发生金属回线接地故障;建议在并联型多端系统中不采用移相处理策略清除金属回线接地故障。高压T区保护采用差动原理,保护动作后,建议相关站采用极闭锁策略。逆变站故障后延时分断换流变网侧开关有利于阀的关断。逆变站换相失败后,更大的直流电流将流经换流阀,需在工程设计环节加以考虑,防止交流系统故障引起的换相失败导致直流过流保护动作。更多还原

【Abstract】 The paper introduced the protection zone, locations of current transformers and switches, as well as modes of system operating for a protection system in a parallel-type multi-terminal high voltage direct current(HVDC) transmission. In multi-terminal HVDC, when a DC line protection was designed to trip correctly for a fault throughout the whole line, the DC line protection maybe trip wrongly for a fault outside of the line. In a substation, each DC line allocates a DC line protection. Each DC line protection is set several setting groups which are set to suit lines with a different length. These setting groups are switched over according to the operating states of other substations. When a fault at a branch line occurs, the faulted branch line can be cleared, while the isolated converter connected to the faulted line must be blocked. In a metallic return mode of multi-terminal HVDC, it is impossible to distinguish a grounded fault of the metallic return line by detecting the electrode line current. A fault clearing action is not suggested for clearing the grounded fault of the metallic return line in multi-terminal HVDC system. A differential current protection principle is suggested to be applied to a high voltage T zone, and it is suggested to block the corresponding poles after the protection operates. Delay tripping AC breaker can help to shutdown the valve in the inverter. In a multi-terminal HVDC system, a larger DC current will flow through the valve when a commutation failure occurs. This phenomenon should be considered in designing the substation so as to avoid the operation of DC over-current protection due to a commutation failure, which is caused by faults in AC systems.更多还原