能量积分型有源配电网无功电流差动保护

doi:10.19595/j.cnki.1000-6753.tces.250119

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Abstract

A significant amount of renewable energy is integrated into the distribution network in the form of inverter-based distributed generators (IBDGs), which transform the traditional distribution networks into active distribution networks. The integration of numerous distributed generators (DGs) has increased the complexity of topology and fault characteristics in active distribution networks. Specifically, the weak fault current contribution of IBDGs and T-connected unmeasurable branch loads have reduced the sensitivity of traditional current differential protection in active distribution networks, sometimes even causing maloperation. To address these issues, an energy integral based reactive current differential protection method is proposed.
Firstly, the reactive differential current is defined as the sum of the reactive components of fault currents at both sides of the protected feeder. Based on the distinct characteristics of nonlinear energy integral value of reactive differential currents during internal and external faults, an energy integral based reactive current differential protection criterion is established. The nonlinear energy integral value is sensitivity to the amplitude and frequency variations of reactive differential current. The energy value is zero when either amplitude or frequency becomes zero. Under normal operation or external faults, the reactive differential current remains zero or consists of a DC component (the frequency of DC components is zero), resulting in an energy integral value equaling zero. However, during internal faults, the reactive differential current contains decaying power frequency components or double power frequency components, leading to significantly large energy integral values. The unbalanced reactive differential current caused by unmeasurable T-connected branch loads manifests as a DC component, and its energy integral value equals zero. In contrast, the reactive differential current resulting from internal short-circuit faults contains decaying power frequency components or double power frequency components, yielding a significantly large energy integral value. This distinction enables the proposed method to be applicable to feeders with unmeasurable T-connected branch loads while requiring only current information from both ends of the feeder.
Subsequently, a 10kV active distribution network simulation model was built in PSCAD. The simulation results show that the proposed method effectively mitigates the impact of crossing currents on current differential protection during internal high-impedance faults. Additionally, it addresses the challenges of distinguishing unbalanced currents caused by unmeasurable T-connected branch loads from fault currents due to internal short-circuits. This approach reliably discriminates internal and external faults and exhibits certain ability to withstand data synchronization errors. Furthermore, two smart terminal prototypes with 5G communication capabilities were developed, and a RTDS closed-loop testing system was established for hardware-in-the-loop validation. The experimental results demonstrate that the fault clearance time of the prototype ranges from 64.6ms to 79.2ms. With effective communication, the prototypes achieved 100% accuracy in short-circuit faults identification.
The simulations and hardware-in-the-loop experiments yield the following conclusions: (1) The proposed method only requires current information from both sides of the protected feeder and is applicable to feeders with unmeasurable T-connected branch loads while accurately identifying all types of internal and external short-circuit faults. (2) Compared with traditional current differential protection, the proposed method demonstrates superior ability to withstand transition resistance and reliably identifies high-impedance faults even when crossing currents exist in the protected feeder. (3) The method remains effective regardless of power source characteristics, showing consistent sensitivity in identifying short-circuit faults in active distribution networks with IBDGs, synchronous-based DGs (SBDGs), or even without DGs integration.

Key words： Differential protection reactive current energy integral unmeasured branch loads protection prototype 5G communication

Received: 17 January 2025

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TM77

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	Zheng Xincheng
	Zou Guibin
	Lu Zhe
	Wang Kaiqi
	Li Qingquan

Cite this article:

Zheng Xincheng,Zou Guibin,Lu Zhe等. Energy Integral based Reactive Current Differential Protection for Active Distribution Networks[J]. Transactions of China Electrotechnical Society, 0, (): 20250119-20250119.

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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.250119 OR https://dgjsxb.ces-transaction.com/EN/Y0/V/I/20250119

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