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Omegat pdf4/28/2023 ![]() These rely on the amplitude difference between the two ends. Consequently, some pilot protection schemes based on the ratio of the positive sequence currents at both ends of the protected section are proposed in. Conventional phase-based current differential protection uses the three-phase current to construct a protection criterion but this increases the burden of communication, whereas the protection method in based on negative-sequence current cannot reflect all types of faults. To solve the problems in the above two types of protection, pilot protection schemes using peer-to-peer communication are proposed. In addition, it cannot be extended to the entire distribution network. However, wide-area protection has a high requirement on the reliability of communication, and highly depends on the stability of the master station. In, the relay agents of different protected areas cooperate to perform protection function. ![]() At the same time a backup protection strategy is proposed to solve the problem of communication interruption. In, a three-level hierarchically coordinated system is introduced to enable the protection. Wide-area protection realizes the interaction of multi-terminal information through the smart terminal unit. However, the acquisition of voltage information is difficult in the existing distribution network. This needs to know the voltage and current to calculate the setting value of the impedance. In, a directional distance relay is proposed. If a fault occurs during this period, the correct operation of the protection may not be guaranteed. However, because of fluctuations in DG output, frequent recalculation of the setting value is required and this can be time-consuming. If there is a significant change in the network, the optimum protection settings are established. In, an adaptive overcurrent protection scheme is proposed, where the fault currents for all the simulated faults are saved. Recently, researchers have proposed three types of new protection schemes based on local, dual-terminal, and multi-terminal information.Īdaptive protection adjusts the threshold value in real-time under the current network topology to meet the protection requirements. Therefore, it is necessary to introduce a protection scheme for an active distribution network with different types of DGs. However, IIDGs have more complicated fault characteristics than rotating-type distributed generators (RTDGs). Inverter-interfaced distributed generators (IIDGs) are widely used because of their flexible control strategy. Because of the above factors, it is difficult to set the threshold value for conventional overcurrent protection, and its protection range, sensitivity and reliability are severely affected. On the one hand, DGs cause bi-directional power flow and uncertain magnitude and direction of load current and fault current, while on the other, the output currents of DGs that use solar and wind energy fluctuate. The emergence of DGs has changed the power flow and fault current characteristics of the network. With increased numbers of distributed generators (DGs) being connected to the distribution network, the conventional network has become an active distribution network.
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