Optimization Method for Combination of Residual Current Protection and Coincidence Brake Logic in a Low-Voltage Distribution System

doi:10.16183/j.cnki.jsjtu.2023.438

Abstract

Abstract:

Low-voltage distribution systems frequently experience leakage current accidents. However, it is challenging to distinguish fault characteristics in abnormal operating conditions, such as electric shock to biological organisms and three-phase imbalance, which leads to the improper operation of existing residual current protection devices, making it difficult to balance both the safety and continuity of power supply in low-voltage distribution systems. Therefore, an optimization method is proposed for combination of the residual current protection and the coincidence reclosing logic to address the ground fault caused by the leakage of the low-voltage distribution system. First, the residual current protection device and the automatic reclosing switch are installed in the low-voltage side outlet of the transformer. When the over-threshold residual current of the fault phase is detected, the instantaneous skip circuit breaker is used to ensure the safety of the power supply. Then, the robust empirical mode decomposition-approximate entropy value and the intrinsic mode function-time domain eigenvalue of the residual current signal are extracted, followed by the establishment of a genetic algorithm-backpropagation over-threshold status identification neural network. Finally, based on the neural network model, the electrical and three-phase imbalance characteristics are effectively separated. The action logic of the residual current protection value setting algorithm and the automatic coincidence brake is optimized to ensure the continuity of power supply. The simulation analysis shows that the error of the classification results of the model after seven iterations is only 9.49×10^-9 with a correlation coefficient of 0.99, confirming the feasibility of the proposed method.

Key words: low-voltage distribution system, bio-electrocution, residual current protection, robust empirical mode decomposition (REMD), automatic reclosing

CLC Number:

TM732

XU Han, ZHU Sanli, ZHANG Tengfei, CHEN Shu, LIU Mingxiang. Optimization Method for Combination of Residual Current Protection and Coincidence Brake Logic in a Low-Voltage Distribution System[J]. Journal of Shanghai Jiao Tong University, 2025, 59(7): 901-911.

Figures/Tables 12

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References 26

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电气设备或模型	参数	值或调节范围
电源	电源电压/kV	10.5
变压器	一次侧额定电压/kV	10
	二次侧额定电压/kV	0.4
线路	正序电阻/Ω	0.01273
	零序电阻/Ω	0.3864
电弧模型	耗散功率/W	0.1~1
	时间常数	1×10^-4~1×10^-3
人体阻抗模型	皮肤电阻/kΩ	1~100
	皮肤电容/nF	20
	生物体内部电阻/Ω	1000
配电线路	接线形式	TN-C
		TN-S
		TN-C-S

样本序号	A相负荷/kW	B相负荷/kW	C相负荷/kW	I_A/A	I_B/A	I_C/A	I₀/mA	γ/%
1	2.55	2.55	0	9.96	10.03	0.068	37.41	99.36
2	3.40	1.28	0.43	8.08	7.13	2.760	38.81	65.89
3	6.80	2.55	0.85	16.06	14.21	5.470	39.15	65.95
4	5.95	1.70	2.25	16.22	9.87	12.390	30.33	39.19
5	10.20	0	0	26.54	0.08	0.080	75.19	70.51
6	7.51	2.55	0	14.94	14.91	0.071	49.53	99.53
7	6.00	6.00	0	23.45	23.52	0.070	37.62	99.71
8	4.50	1.28	0.55	9.13	7.60	3.580	43.11	60.85
9	5.10	0	0	0.26	0.08	0.080	74.82	70.46

状态	样本编号	IMF1	IMF2	IMF3	IMF4	IMF5	IMF6	IMF7	IMF8	a
生物体触电	1	3.44×10^-4	8.17×10^-4	4.89×10^-4	1.60×10^-4	2.92×10^-4	1.62×10^-4	1.94×10^-4		2.375
	2	2.12×10^-3	1.74×10^-3	2.11×10^-4	1.75×10^-4	1.78×10^-4	2.40×10^-4	1.39×10^-4		0.82
	3	5.12×10^-4	9.88×10^-4	6.53×10^-4	4.31×10^-4	1.72×10^-4	2.43×10^-4	1.94×10^-4	1.51×10^-4	1.93
	…	…	…	…	…	…	…	…	…
	79	1.76×10^-3	7.82×10^-4	4.13×10^-4	3.69×10^-4	2.19×10^-4	1.19×10^-4	1.92×10^-4		0.84
	80	1.35×10^-3	1.26×10^-3	5.83×10^-4	4.88×10^-4	2.90×10^-4	7.33×10^-4	1.60×10^-4	1.95×10^-4	0.93
三相不平衡	81	2.15×10^-3	1.94×10^-4	3.49×10^-4	2.78×10^-4	1.01×10^-4				0.09
	82	1.97×10^-4	2.51×10^-4	2.28×10^-4	1.68×10^-4	2.58×10^-4	2.13×10^-4			0.47
	83	2.04×10^-3	1.17×10^-3	4.34×10^-4	3.11×10^-4	2.08×10^-4	1.98×10^-4			0.87
	…	…	…	…	…	…	…	…	…
	159	2.06×10^-3	3.46×10^-4	3.19×10^-4	2.14×10^-4	2.17×10^-4	2.34×10^-4			0.16
	160	2.05×10^-3	3.41×10^-4	3.22×10^-4	1.54×10^-4	2.83×10^-4	2.54×10^-4			0.17

样本编号	IMF	标准差	裕度因子	能量值	样本编号	IMF	标准差	裕度因子	能量值
1	1	5.32×10^-1	1.76	2.73×10⁴	81	1	4.15	8.02×10^-1	1.03×10⁶
	2	1.55×10^-1	43.1	2.41×10³		2	10.22	2.07×10^-1	6.60×10⁶
	3	3.10×10^-1	15.4	7.69×10³		3	13.44	1.73×10^-1	1.09×10⁷
	4	1.74×10^-1	11.1	4.84×10³		4	2.73	1.54×10^-1	9.14×10⁵
	5	8.57×10^-2	7.85	1.10×10³		5	2.81	6.12×10^-1	4.85×10⁵
	6	3.67×10^-2	75.4	1.18×10²		6	1.38×10^-2	1.24×10^-2	13.28
	7	3.33×10^-2	50.6	92.99		7
	8					8
2	1	4.34×10^-1	2.32	1.85×10⁴	82	1	3.09	1.04	5.76×10⁵
	2	1.36×10^-1	71.8	1.69×10³		2	6.28×10^-1	4.31	2.90×10⁴
	3	1.90×10^-1	26.11	3.09×10³		3	2.11	1.52	2.71×10⁵
	4	1.40×10^-1	17.02	1.59×10³		4	2.89	8.97×10^-1	6.90×10⁵
	5	1.29×10^-1	15.57	2.06×10³		5	6.83×10^-1	2.85×10^-1	1.04×10⁶
	6	3.15×10^-2	28.87	1.41×10²		6	1.97	1.47	2.37×10⁵
	7	5.94×10^-2	29.83	2.84×10²		7
	8	2.08×10^-2	1.27×10²	37.2		8
……	……
80	1	9.79×10^-2	32.74	8.82×10²	160	1	3.46	9.66×10^-1	7.21×10⁵
	2	7.69×10^-2	63.74	5.08×10²		2	8.75×10^-1	6.6	4.64×10⁴
	3	7.54×10^-2	1.19×10²	4.78×10²		3	2.53×10^-1	9.34	3.84×10³
	4	3.76×10^-2	61.54	1.14×10²		4	4.45×10^-2	43.6	1.27×10²
	5	4.65×10^-2	48.45	1.81×10²		5	3.55×10^-2	57.8	82.46
	6	4.31×10^-2	41.25	3.16×10²		6	1.90×10^-3	1.40×103	2.30×10^-1
	7	5.06×10^-3	2.69×10²	3.34		7
	8	3.37×10^-3	5.11×10²	9.28×10^-1		8