【作者】 刘丽丽；

【导师】 金恩淑；

【作者基本信息】 东北电力大学 ， 电力系统及其自动化， 2008， 硕士

【摘要】 差动保护是变压器的主保护,正确区分励磁涌流和内部故障对变压器保护是至关重要的。由于多种原因差动保护已经不能保证正确动作。然而,基于等值回路、磁特性等原理的保护摆脱了变压器励磁涌流以及过励磁的影响,能够快速可靠的动作。但它们的实现都需要变压器原副边绕组的漏感和电阻作为先验参数。而目前尚没有准确的同时求取变压器绕组参数的方法,通常的短路实验只能测得两侧参数的和值。对此,本文提出了新的变压器绕组参数辨识方法,并讨论了对输入信号的要求和影响辨识精度的因素。为了验证算法的准确性,将离线辨识出的参数应用于基于磁通增量的变压器保护。EMTP仿真及动模实验结果表明:该方法通过采用正确的输入信号及参数,能够同时准确的辨识出变压器各侧绕组的漏感及电阻;将辨识出的参数与真实参数分别应用于基于磁通增量的变压器保护,两种方法均能保证保护正确动作。最后,提出了一种基于参数在线辨识的变压器保护,即当变压器进入暂态时开始参数辨识,以离线辨识出的参数为初值,采用带阻尼项的最小二乘递推法对参数进行在线辨识,利用内部故障时参数发生较大变化而其它情况下参数不变的特点来判别内部故障。该保护动作速度快,具有较大的门槛裕度,具有很好的应用前景。EMTP仿真及动模实验表明,该保护在各种情况下均能正确快速的动作。更多还原

【Abstract】 The differential protection has been the main protection technique for transformers. The correct discrimination between the inrush current and the fault current is crucial to the technique. However, by many factors, the differential protection can not completely avoid mal-operation. The algorithms based on equivalent circuit and characteristics of flux are not affected by the inrush and over-excitation current.They both can operate reliablely and quickly.However, the leakage inductance and resistance of each side of the thransformer are required as priori parameters.At present, there is no accurate algorithm on the identification of winding parameters. Only the sums of the parameters of the two sides can be got by the usual short-circuit experiment.So a new method is proposed to identify the parameters in this paper. The input signal and factors that influence the accuracy of identification are discussed. In order to verify the correction of this method, the identified parameters are used in the transformer protection based on the increment of flux linkages. The simulation results of EMTP and dynamic experiments show that the method can identify the parameters of each side accurately if use the correct input signal and parameters; when the identified parameters and the true parameters are applied to the transformer protection based on the increment of flux linkages, the two methods both can gurrentee it operate correctly.Finally, a transformer protection based on the parameter identification on line will be described in this paper. The program becomes to identifiy the parameters when the transformer is disturbed. Recursive damped least square which use the parameters identified off line as the initial parameters is proposed to identify the parameter on line.The inner fault can be detected because the leakage inductance will change when inner fault. It can act quickly and the threshold is very small.This protection has a good prospect. The simulation results of EMTP and dynamic eexperiments show that this protection can operate correctly under all situations.更多还原