注入信号法发电机定子接地保护受定子绕组对地电容的影响，灵敏度较低，难以满足大型机组高灵敏度继电保护的要求。而采用外加小电抗器、选择合适的注入信号频率，以补偿定子绕组对地容抗、测量故障接地电阻或测量信号电压、信号电流相位差进行接地保护则可改善大型机组定子接地保护的灵敏度。计算、分析与仿真表明：该方法具有较高的灵敏度。

A principle for resonance measurement based on injectingresonant frequency signal is presented in this letter. The groundingcapacitance of lines and equipment and the grounding fault resistancecan be measured on-line in ineffectively grounded systems.Petersen-coil automatic tuning is implemented, and 100% statorgrounding fault protection for generator stator windings is also proposed.The prototype for Petersen-coil tuning has been tested on networksfor many years. In addition the new method for generator statorgrounding fault protection is verified by simulation.

Fault location using traveling wave has been applied inextra-high voltage power grids successfully. Due to itscomplication and high cost, it is not easy for this technique to beaccepted for use in distribution system. A new traveling wavefault location system is developed simply in a cost-effective wayfor power networks (especially for distribution system) in thispaper. Two traveling wave sensors are developed to capture thecurrent traveling wave flowing from the capacitive equipment toearth and the voltage traveling waves in all three phases. Theoutputs of the sensors are then applied to the trigger and timetagging by using Global Position System (GPS) receiver. Thefault position is calculated by the traveling wave arrival times inevery power station where only one fault locator is installed. Thefault location system is tested in the power system. Testing resultsshow that the fault locator has high precision and robustness.

受干扰、卫星失锁等因素的影响，全球定位系统（GPS）时钟难以满足高可靠性同步控制领域的要求。文中根据高精度晶振与GPS时钟精度互补的特点，采用高精度晶振对GPS时钟进行监测，建立了最小二乘估计模型，估计出GPS时钟的方差及晶振的累计误差，给出了GPS时钟误差的在线修正方法，研制出了具有较高性能价格比的高精度时钟发生装置，并成功地应用于电力系统继电保护与控制。

介绍了能同步记录并分析电力系统各种扰动变化过程的GPS同步暂态录波仪及其软件系统。介绍了基于暂态录波仪的输电网故障行波定位系统。该仪器性能可靠、操作方便并通过了模拟试验。