【作者】 徐雁；

【导师】 叶妙元；

【作者基本信息】 华中科技大学 ， 电气工程， 2004， 博士

【摘要】 高压直流输电作为电力系统的一个发展方向,在我国的国民经济中发挥着越来越重要的作用;在直流输电中,研究运用新的高压直流测量方法和技术已成当务之急。本研究是结合“西电东送”直流工程国产化的要求而进行的。本文在全面比较分析直流电流和直流谐波电流测量方法的基础上,确定分流器和空心线圈为传感器,以光纤传输信号和能量,结合光电技术、微计算机技术,系统地分析了光电直流电流和谐波电流互感器的工作原理及影响其测量的多种因素,提出了解决问题的具体方法和措施。分流器测量电流具有不受磁场干扰及结构简单的属性,特别是结合光纤传输一举改变分流器无法隔离的不足为便于实现高低压电隔离的优点,较之其它方法用于高压测量具有明显优势。本文首先分析分流器受温度和应力的影响,分析表明:分流器在温度变化的情况下,电阻值的变化会影响输出;然而温度变化的应力影响则与上述影响相反,可以部分抵消。对于其它影响因素,分析原因并研究给出了相应的解决方法。只要采用适当的方法和技术,可保证分流器良好的稳定性,达到0.2级的测量准确度。空心线圈用于直流谐波电流的测量,不受直流分量影响,并具有良好的频率特性。本文重点研究空心线圈线性度,频率响应和响应灵敏度的关系。空心线圈的结构尺寸只影响其感应系数的大小,不影响其线性;其线性度主要取决于线圈的匝密度和截面积的均匀一致性;惯性环节解决了系统响应灵敏度与下限频率的矛盾。针对小信号谐波电流的测量,提出了单线圈等安匝模拟和多线圈叠置结构两种方法。光电、电光转换为光电互感器的重要组成部分,针对直流和谐波电流的不同要求,分别采用数字与模拟两种不同的光电、电光转换及传输方式,分析比较了各自的特点。光供电和高压电路的低功耗要求是该互感器面临的新问题,本研究提出独创的单纤传信号方式,能显著降低高压侧电路功耗。结合低功耗设计和光供电,我们在国内首次实现了高压光供电直流电流及谐波电流的测量。本研究在电磁兼容设计、绝缘设计及直流大电流和谐波电流的试验方法上,有针对性地做了些许研究,对系统各部分作了大量的试验,研制的120kV 0.5级样机在西安高压电器研究所通过了型式试验。更多还原

【Abstract】 High Voltage Direct Current (HVDC) transmission network plays a critical role in our economy. We can measure some important quantities in HVDC transmission system by using new principles and new technologies. An Optic-electric Current Transformer (OCT) applied to direct and harmonic measurement is discussed in detail here. This work is in agreement with the requirement of the “Transmission of Electricity in Western Parts to Eastern Parts” in China.Based on analysis of the measurement methods for direct and harmonic current, the properties for the high voltage current transducer with air core coil and ohmic shunt is examined, then the transmission of signal and energy through optic fiber is proposed. The principle of this OCT and the main factors affecting the measurement are analyzed, and last the detailed measurement technologies are suggested.The main advantages of shunt are simple in the structure and no magnetic interference. The voltage drop across the shunt is digitized; digital signal is transmitted via an optic fiber link to ground potential. Therefore, the secondary circuits can be isolated from the primary part of the transducer. The measuring result can be changed by temperature and stress. However, the result shows that the affects produced by temperature could offset in part that result from the stress. By means of the available method and technology, high stability and accuracy (( 0.2%) of shunt can be reached.Air core coil as a sensor for harmonic current possesses an excellent dynamic performance. Because the output from the coil is proportional to the time derivative of the current, the obtained result is not connected to direct current. The linearity of the sensor is connected to well-distribute of the coil. The integrator designed specially can gain lower frequency and provide high sensitivity. Two methods designed as the “equal- ampere” and the scheme of complex coils that can be applied to the weak signal is proposed.Digital and analog signals are converted to light and transmitted by optic fiber respectively; <WP=6>they have different functions and distinguishing feature. The communication through signal optic fiber is explored for the first time. Test shows that power consumption of high voltage circuit is decreased obviously. Lower power consumption could improve reliability of OCT.The designs in the electromagnetic compatibility and insulation are also studied here. Because OCT belongs to electronic transformer and its secondary output is at low level, it is difficult to calibrate OCT by conventional calibrator. Therefore, new calibration methods are proposed. The calibration tests have been operated. A sample OCT for 120kV 0.5 classes is designed and made. The type tests are done in Xi’an High Voltage Apparatus Research Institute.更多还原