磁通密度特征分析与CT饱和区识别及重构技术

doi:10.11930/j.issn.1004-9649.202302075

摘要/Abstract

摘要：

为解决电流互感器饱和引起的继电保护问题，提出了一种基于磁通密度特征的电流互感器（current transformer，CT）饱和识别方法，以及畸变区二次电流重构技术。首先以饱和时磁通密度梯形区域特征为基础，对CT饱和进行识别，进而利用磁通方差的斜率在进入饱和与退出饱和的差异构建饱和判据，并计算二次电流饱和起点和终点对应的时间，以此得到CT饱和区。然后以电网负荷最大时的电流为依据构建保护启动判据，避免保护误动。最后利用最小二乘法对饱和区二次电流进行重构，可靠反映系统一次电流。基于PSCAD/EMTDC软件的仿真验证表明，所提方法准确可靠，能快速有效识别CT饱和区段，且时间误差不超过1 ms。

关键词: CT饱和, 磁通密度, 饱和补偿, 电流重构, 最小二乘法

Abstract:

To solve the problem of relay protection caused by CT saturation, a CT saturation identification method is proposed based on flux density characteristics and secondary current reconstruction technology in the distortion area. The CT saturation is identified based on the characteristics of the magnetic flux density trapezoidal region at saturation. Then the saturation region of CT is obtained using the slope of the flux variance to construct the saturation criterion based on the difference between entry saturation and exit saturation and calculate the time corresponding to the start and end point of secondary current saturation. The protection starting criterion is constructed based on the current at the maximum grid load to avoid protection misoperation. Finally, the least square method is used to reconstruct the secondary current in the saturation region to reflect the primary current reliably. The simulation results based on PSCAD/EMTDC software show that the proposed method is accurate and reliable, and can quickly and effectively identify the saturated CT segment with a time error of less than 1 ms.

Key words: CT saturation, magnetic flux density, saturation compensation, current reconstruction, least square method

中图分类号:

TM77

王峰, 朱佳, 焦邵麟, 李一泉, 谢华, 赵青春. 磁通密度特征分析与CT饱和区识别及重构技术[J]. 中国电力, 2023, 56(10): 179-185, 193.

Feng WANG, Jia ZHU, Shaolin JIAO, Yiquan LI, Hua XIE, Qingchun ZHAO. Magnetic Flux Density Feature Analysis and CT Saturation Region Recognition and Reconstruction Technology[J]. Electric Power, 2023, 56(10): 179-185, 193.

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链接本文: https://www.electricpower.com.cn/CN/10.11930/j.issn.1004-9649.202302075

https://www.electricpower.com.cn/CN/Y2023/V56/I10/179

图/表 13

图 1 CT饱和时二次电流及磁通密度波形

Fig.1 The waveform of secondary current and flux density at CT saturation

图 2 单机无穷大电网

Fig.2 Grid of single-machine infinite bus

图 3 |Bmax|=0.5时电流波形及判断结果

Fig.3 The current waveform and judgment result with |Bmax|=0.5

表 1 |Bmax|=0.5时检测时间及误差

Table 1 The detection time and error with |Bmax|=0.5

饱和次数	饱和开始时间/s		误差/s	饱和结束时间/s		误差/s
饱和次数	实际	检测	误差/s	实际	检测	误差/s
1	1.004	1.005	–0.001	1.013	1.013	0
2	1.018	1.018	0	1.022	1.021	0.001
3	1.025	1.026	–0.001	1.033	1.033	0
4	1.038	1.038	0	1.041	1.041	0

图 4 轻度饱和时电流波形及判断结果

Fig.4 The current waveform and judgment result at mild saturation

图 5 严重饱和时电流波形及判断结果

Fig.5 The current waveform and judgment result at severe saturation

表 2 轻度饱和时检测时间及误差

Table 2 The detection time and error at mild saturation

饱和次数	饱和开始时间/s		误差/s	饱和结束时间/s		误差/s
饱和次数	实际	检测	误差/s	实际	检测	误差/s
1	1.010	1.009	–0.001	1.015	1.015	0
2	1.025	1.026	–0.001	1.035	1.034	0.001

表 3 严重饱和时检测时间及误差

Table 3 The detection time and error at severe saturation

饱和次数	饱和开始时间/s		误差/s	饱和结束时间/s		误差/s
饱和次数	实际	检测	误差/s	实际	检测	误差/s
1	1.004	1.005	–0.001	1.013	1.013	0
2	1.018	1.018	0	1.022	1.021	0.001
3	1.025	1.026	–0.001	1.033	1.033	0
4	1.038	1.038	0	1.041	1.041	0

图 6 噪声影响下电流波形及判断结果

Fig.6 The current waveform and judgment result under the influence of noise

表 4 噪声干扰下检测时间及误差

Table 4 The detection time and error under the influence of noise

饱和次数	饱和开始时间/s		误差/s	饱和结束时间/s		误差/s
饱和次数	实际	检测	误差/s	实际	检测	误差/s
1	1.004	1.005	–0.001	1.013	1.013	0
2	1.018	1.018	0	1.022	1.021	0.001
3	1.025	1.026	–0.001	1.033	1.032	0.001
4	1.038	1.038	0	1.041	1.041	0

图 7 轻度饱和电流补偿

Fig.7 Current compensation under mild saturation

图 8 严重饱和电流补偿

Fig.8 Current compensation under severe saturation

图 9 噪声影响下饱和电流补偿

Fig.9 Saturation current compensation under the influence of noise

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