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Double-circuit transmission lines play a very important role in electric power transmission. When a line-to-line nongrounded fault occurs on double-circuit transmission lines, for traditional tripping and reclosing methods, tripping of all six phases may cause power system instability, and fixed time autoreclosing may reclose the double-circuit transmission lines to a nonextinguished fault. In this paper, a novel tripping strategy is proposed; when a line-to-line nongrounded fault occurs, some part of the electric power can be transmitted after tripping, and many kinds of nongrounded faults can be equivalent to a single-phase to ground fault. Furthermore, reactive power characteristics are adopted to determine the fault extinction. Finally, an adaptive autoreclosing scheme for line-to-line nongrounded faults on double-circuit transmission lines based on phase-to-phase reactive power is proposed. The accuracy and feasibility of the propose method are verified by relevant simulation experiments, and multiple operation conditions are considered.INDEX TERMS Adaptive algorithm, current-voltage characteristics, fault detection, grounding, power system protection, power system reliability, reactive power, transmission lines. NOMENCLATURE Phase IXPhase X in line I, X=A, B, or C. Phase IIX Phase X in line II, X=A, B, or C. BVBasic values assigned to the fault phases. Situation A1 SAFPs exist, and the selected SAFPs were determined as nontripped at last trip. Situation A2 SAFPs exist, and the selected SAFPs were determined as nontripped at the time before the last trip. Situation A3 SAFPs exist, and the selected SAFPs were not determined as nontripped in two recent trips. Situation B1 SAFPs do not exist, and the fault phase was determined as nontripped at last trip.The associate editor coordinating the review of this manuscript and approving it for publication was Gerard-Andre Capolino.Situation B2 SAFPs do not exist, and the selected fault phase was determined as nontripped at the time before the last trip. Situation B3 SAFPs do not exist, and the selected fault phase was not determined as nontripped in two recent trips. UmXNEquivalent m-end voltages of the sound phases in the same circuit, X=A, B, or C. UnXNEquivalent n-end voltages of the sound phases in the same circuit, X=A, B, or C. N Sound phase quantity in the same circuit. UmXMEquivalent m-end voltages of the sound phases in the different circuits, X=A, B, or C. UnXMEquivalent n-end voltages of the sound phases in the different circuits, X=A, B, or C.

With the increasingly serious environmental problems, the concept of environmental protection has been deeply rooted in people's minds. The development of small‐ to medium‐sized enterprises (SMEs) is also highly concerned, but such technology‐led enterprises are still subject to more constraints in financing. This paper introduces the loan guarantee insurance, establishes the income model of each participant under the two financing modes of traditional accounts receivable financing and accounts receivable financing under the cooperation of bank and insurer, and explores the role of loan guarantee insurance in financing of SMEs based on the Stackelberg game model. If the manufacturer's default risk premium is high, at the same time, when the loan interest rate announced by the bank under bank‐insurance cooperation is lower than the traditional model, the manufacturer under the loan guarantee insurance model produces and sells more products. However, while guaranteeing their own profits, the bank and insurer can lower the loan interest rate and insurance premium rate as far as possible, which can stimulate the market. By analyzing the complexity of the system, it is found that the decision‐maker's choice of adjusting speed and initial value affects the development state of the system.