发电机接地系统参数试验方法现场应用

Field application of test methods for generator grounding system parameters

定子绕组对地电容参数是各种接地装置设计的基础,接地装置是否满足要求需通过试验进行验证。小容量发电机电容电流较小,接地装置参数均通过定子绕组对地集中电容进行设计,几乎均未做试验验证。对于大中型水轮发电机,电容电流较大,实测集中电容与分布等效电容相比误差达17%以上,若不通过试验验证,则可能因接地装置参数设计不当引起安全事故。本文提出发电机中性点不对称电压、位移电压、单相接地最大电容电流、单相接地最大故障电流四种参数的试验方法。在发电机中性点接入接地装置前后,通过模拟故障开展发电机中性点接地系统参数试验,确定发电机中性点接地方式及接地装置参数是否满足工程要求。该试验方法已在多个大中型水轮发电机和个别汽轮发电机进行验证,用该方法测试参数设计的接地装置运行稳定可靠。

The parameters of the stator winding capacitance to ground are the basis for the design of various earthing devices,and whether the earthing device meets the requirements needs to be verified through testing.For small-capacity generators with small capacitance currents,the grounding device parameters are designed by means of the centralized capacitance of the stator winding to ground,and almost no tests are carried out to verify this.For large and medium sized hydro generators,the capa-citance current is large and the measured concentrated capacitance has an error of more than 17%compared to the distributed equivalent capacitance,which may cause safety accidents due to improperly designed earthing device parameters if not verified through tests.The paper proposes test methods for four parameters:generator neutral asymmetric voltage,displacement voltage,single-phase grounding maximum capacitance current and single-phase grounding maximum fault current.Before and after the neutral point of the generator is connected to the grounding device,the parameter test of the generator neutral grounding system is carried out by simulating faults to determine whether the generator neutral grounding method and the parameters of the grounding device meet the engineering requirements.This has been verified on several large and medium-sized hydro generators and individual turbine generators,and the earthing devices designed with the test parameters of this test method are stable and reliable in operation.