中性点直接接地电网的自适应零序电流速断保护

为了尽可能减小线路零序电流速断保护的保护范围受系统运行方式变化等因素的影响,提出了一种自适应零序电流速断保护的实现方法。该方法假设输电线路两侧的保护之间具有通信通道,系统发生短路时线路两侧的保护能够实时计算出系统等值阻抗并经通信通道实时传送给对侧的保护,两侧的保护装置可根据短路类型实时调整零序电流速断保护的动作整定值。通过计算不同接地短路类型时零序电流速断保护灵敏度的公式,表明零序电流速断保护的保护范围不仅受系统运行方式变化的影响,还受接地短路类型的影响。仿真计算结果表明,文章提出的自适应式零序电流速断保护的实现方法可有效减小系统运行方式变化及短路类型不同对保护范围的影响,使保护的性能大大提高。

Adaptive Instantaneous Zero Sequence Current Protection in the Neutral Directly Grounded Power Systems

In order to reduce influences of varieties of operation conditions of power systems and differences of grounded fault type on the protecting range of the instantaneous zero sequence current protections of transmission lines,a feasible method for realizing the adaptive instantaneous zero sequence current protections was put forward.The method supposes that the protection devices of ends of a transmission line could calculate real-time equivalent impedances of a power system of the back of the place of device installation when fault occurs,and the devices could send the calculation results each other by communication channel very rapidly.In this way,the protection device could distinguish the type of grounded fault,and it adjusts the setting of the instantaneous zero sequence current protection based on the operation conditions of power system and the type of grounded fault in real-time.A double ends source power system for simulation example was adopted to calculate individually protecting range of different grounded fault types on maximum operation conditions and minimum operation conditions of power system,and the adaptive instantaneous zero sequence current protections were compared with the traditional instantaneous zero sequence current protections.The simulation results indicate that the protecting range of the device is seasoned with changes of operation condition and of grounded fault type,and the proposed method will remarkably limit the affection caused by varieties of operation conditions of power system and differences of grounded fault type.It can keep the performance of protection optimal.