利用磁环构造配电线路边界的单端量全线速动保护(1)：磁环边界特性及模型

Aiming at the problem that it is difficult for the converters to cooperate in the existing single-ended protection caused by the flexible and variable topology of the distribution network with multi-converters, a novel boundary protection scheme based on the magnetic rings is proposed to realize the whole-line quick-action with single-ended electrical quantity. In this paper, the characteristics of the magnetic ring are introduced first. On this basis, the impedance characteristics of the magnetic ring are tested. The test results show that the power frequency and DC impedance of the magnetic rings is small while it is far bigger when the frequencies are higher, so it has the advantage of not affecting the normal operation of the system when acting as a line boundary. A wide-band modeling method for the magnetic ring is proposed, including the fitting of the frequency-dependent parameters, the circuit synthesis method and the simulation of saturation characteristics. Finally, a parameter correction method for different sizes and numbers of magnetic rings is introduced. The comparison between the experiment and the simulation results verifies the validity of the equivalent model, which lays a foundation for subsequent theoretical analysis and emulation verification.