Impact of Impulse Current on Current Protection in Fault Recovery and Closing of Active Distribution Networks with Soft Open Point

doi:10.16183/j.cnki.jsjtu.2024.194

Abstract

Abstract:

In distribution networks with distributed generation (DG), employing a soft open point (SOP) to replace a tie switch during fault recovery enables load transfer and simultaneous voltage support for distributed generations. However, the bidirectional breaker closure enabled by SOP can induce surge currents when the voltages on the two sides are not aligned, potentially compromising system security if not controlled. This paper treats the phase difference between the SOP-supported voltage during fault recovery and the system power supply voltage as a principal source of the closing surge current, and also accounts for the voltage phase jump at the DG interconnection point. The total closing surge current is expressed as the superposition of two contributing parts with their physical interpretations provided. A simplified formula for the total closing surge current is proposed of which the correctness and reasonableness is validated by time-domain simulations on a standard distribution network model. The impact of the closing surge on system-side current protection is examined and an upper bound on the permissible DG capacity for the network is identified based on a limit analysis of the maximum surge current. The results indicate that over-sized DG capacity may pose a risk of failure in protection actions.

Key words: distributed generation (DG), soft open point (SOP), surge current, fault recovery, current protection

CLC Number:

TM762.2

YANG Zengli, WANG Ruoqi, HU Yan, FAN Chunju, WANG Jing. Impact of Impulse Current on Current Protection in Fault Recovery and Closing of Active Distribution Networks with Soft Open Point[J]. Journal of Shanghai Jiao Tong University, 2026, 60(2): 270-276.

Figures/Tables 6

Fig.1

Fig.2

Tab.1

Tab.2

Fig.3

Tab.3

Impact of surge current on current protection at various stages

保护类型	电流速断保护	限时电流速断保护	定时限过电流保护
合闸冲击电流是否对保护产生影响	是	是	否
不影响保护准确动作的DG容量限制	$P 2 E ϕ 2 Z s + L' Z l × K r e l I K z - 2 1 + K$	$P 2 E ϕ 2 Z s + L' Z l × K r e l I I K r e l I - 2 1 + K$	$P 2 E ϕ K r e l I I I K s s K r e I L, m a x - 4 E ϕ 2 Z s + L' Z l + Z 1$

Tab.3

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DG出力/ MW	i^*理论值/A	i^*仿真值/A	I_DG,max 仿真值/A	M= I_DG,max/i^*
0.5	29	24	41	1.414
1.0	58	53	82	1.414
1.5	87	82	121	1.391
2.0	115	112	162	1.409

DG出力/ MW	I₁理论值/A	I_DG,max 理论值/A	I_imp理论值/A	I_imp仿真值/A
0.5	455	43	498	495
1.0	455	87	542	507
1.5	455	130	585	530
2.0	455	172	627	566