汽轮发电机次同步自励磁过电流保护

Subsynchronous self-excitation overcurrent protection for turbine generator

托克托电厂安装静态阻塞滤波器(SBF)抑制次同步振荡,由于参数配合不当,曾出现异步自激振荡,为此装设次同步自励磁过电流保护。由对定子绕组次同步电枢电流产生的转子涡流损耗的分析可知:涡流损耗与次同步电枢电流的正序、负序分量的有效值的平方成正比,与转差频率的1.5次方成正比。将次同步电流折算成等效的工频负序电流,实现定时限、反时限的次同步过电流保护,设计了判别次同步电流幅值逐渐增长的发散保护。此外,傅氏滤波算法计算三相工频电流的负序分量时,如果定子绕组有次同步电流分量流过,则会因为算法的原因计算出一个虚假的工频负序分量。最后分析了保护方案的局限性。

A static blocking fiher is installed in Tuoketuo Power Plant for mitigating the SSO（SubSynch- ronous Oscillation） and the improper parameter setting causes asynchronous self-excitation oscillation,for which a subsynchronous self-excitation overcurrent protection is equipped. The rotor eddy loss caused by the subsynchronous stator armature current is analyzed,which shows that,the rotor eddy loss is proportional to the square of the RMS value of its positive and negative sequence components and to the 1.5 power of the slip frequency. The definite-time and inverse-time SSO overcurrent protection is implemented by converting the SSO current into the equivalent negative sequence current at power frequency. A divergent SSO current protection is designed,which detects the increase of SSO current amplitude. If there is SSO current in armature winding,a fake value will be obtained when the Fourier filter is applied to calculate the negative sequence current at power frequency. The limitation of this protection scheme is analyzed.