新能源送出线路非全相运行机理及其对保护的影响研究

Research on Open-phase Operation Mechanism of Transmission Lines Connected to Renewable Power Sources and Its Impact on Protection

摘要:

电力系统运行实践表明，新能源送出线路单相重合闸非全相运行过程中，新能源侧存在过电压和过电流，可能影响保护性能。为揭示送出线路非全相运行机理，首先推导了非全相运行状态下新能源侧电压和电流解析式，并利用实际故障录波数据验证了其有效性；然后，基于推导的解析式，研究了新能源控制方式、功率水平、送出线路长度对过电压、过电流的影响；最后，结合新能源送出系统保护配置情况，分析了送出线路保护和变压器保护对非全相运行状态的适应性。研究结果表明：非全相运行期间健全相电流约上升至额定电流的√3倍，过电压幅值主要受断口阻抗和新能源电源正序等效阻抗的影响；由于同时存在较高的负序电压和过电流，变压器高压侧复合电压过电流保护可能误动作。

Abstract:

The operation practice of power system has shown that overvoltage and overcurrent exist in the system during the open phase operation of outgoing line connected to new energy, which may affect the performance of protection. To reveal the open phase operation mechanism of outgoing line, the analytical expressions of voltage and current on new energy side are derived, and their effectiveness are verified using actual fault recording data. Based on the derived expressions, the effects of new energy control methods, power levels and outgoing line length on overvoltage and overcurrent are investigated. Combined with the protection configuration of the system, the adaptability of outgoing line protection and transformer protection to the open phase operation state is also analyzed. Research results show that during the open phase operation, the current of sound phase rises to about √3times of the rated current, and the overvoltage amplitude is mainly affected by the transmission line′s impedance and the equivalent positive sequence impedance of new energy power. In addition, the compound voltage overcurrent protection on high voltage side of transformer may have malfunction due to the higher negative sequence voltage and overcurrent.