【作者】 张艳；

【导师】 李红斌；

【作者基本信息】 华中科技大学 ， 电工理论与新技术， 2004， 硕士

【摘要】 光学电流传感器是新型电子式电流互感器的一种。与传统电流互感器相比,具有抗电磁干扰能力强、动态范围宽、绝缘结构相对简单、重量轻、易于与微机接口的优点,在电力系统中有着广泛的应用前景。本文首先简要介绍了基于Faraday效应的光学电流传感器的测量原理、常用光学电流传感器的类型及为了提高灵敏度而设计的单光源双光路闭合环路型传感头。接着介绍了光学电流传感器二次信号处理的常用方法,分析出原有计量输出波动的原因,针对存在的问题,基于均方根算法的数值算法原理重新设计了光学电流传感器的计量数字输出方案,采用软件同步采样方式、IIR滤波器、修改平方和子程序流程及DSP与VB间的通讯协议,增加传输的有效位数,提高了测量的稳定性和准确度,并对影响计量数字输出的各种误差源给出了定量分析。由于OCT和CT测量原理及输出型式完全不同,不能使用原有的传统校准系统来校验OCT。以前的OCT校准时,由于没有合适的OCT校准系统,基本上只可对模拟输出的被测电流幅值进行校准,而不能对测量的角差进行校准。作者于2002年参与研制出一套基于DSP的OCT数字信号采集及校准系统,该系统对电源没有特殊要求,可以同时对OCT的比差及角差进行校准,并自动记录到数据库中。此系统已通过湖北省计量局的认证,准确度为0.05级,可用在实验室进行0.2级OCT的标定及试验。本文最后对光学电流传感器样机进行了各项性能测试,试验结果表明,OCT的各项技术指标达到了预期的设计要求。更多还原

【Abstract】 Optical current transformer(OCT) is one of three kinds of new-style electronic current transformers. It has potential benefits over conventional current transformers (CTs) such as inherent high-voltage isolation, immunity to electromagnetic interference, enhancement in signal bandwidth and dynamic range, ease of integration into future digital control and protection systems and will be widely used in power electrical system.Firstly, the paper describes the work principles of OCT based on Faraday effect of crystal; several generally used types as well as the closed-loop structure of sensor head that has single-light-source and dual-light-path. Then several secondary signal-processing methods of OCT are discussed. An analysis is made why the metering output is fluctuated and the reasons are found out. In allusion to existent problems, soft synchronous sampling and IIR digital filter are adopted; the communication protocol between DSP and VB is modified; the flow of DSP algorithm is re-builded, thus the effective data length is increased. As a result, the measurement stability and accuracy is enhanced. The digital output error sources are indicated and their errors are quantified.Due to the difference between CT and OCT in measurement principle as well as output form, the conventional calibration instrument can’t be used to verify the accuracy of OCT. For no appropriate calibration instrument, only the ratio error of OCT can be verified and no way can verify the phase error. In 2002, an automatic data acquisition and scaling system based on DSP was developed and accomplished. This system has no peculiar requirement on power stability and can be used to verify the current error and phase error of OCT synchronously. The measurement data is saved in database according to set command. This system had passed the identification by Hubei institute of Measurement and Testing Technology; its accuracy meets 0.05 class. So this system is suitable to verify 0.2 class OCT in laboratory.Finally, all type tests and EMC tests are done, and the results show that OCT achieves the anticipative design specifications.更多还原