Study on the improvement of measurement accuracy of grid short-circuit parameters based on semi-physical simulation

Short-circuit current calculation is one of the most basic and commonly used calculations in power systems, which is related to the setting of distribution network relay protection, selection of electrical equipment, identification of short-circuit accidents, and so on. This paper establishes the grid structure of grid short-circuit with 220kV substation as the boundary, analyzes the current composition of grid short-circuit, designs the basic method of grid short-circuit current calculation based on the Davignan equivalence model, and calculates its steady-state value. In the calculation of grid short-circuit current parameters, the idea of casting and cutting capacitors is introduced to construct the measurement strategy for short-circuit current capacity parameters. Based on the semi-physical simulation test technology, the semi-physical simulation verification platform of grid short-circuit is established by combining the real-time digital simulation system, and the error between the calculated value of short-circuit current and the simulation measurement value is analyzed by this platform. When the short-circuit capacity parameter is 100MVA, the measurement error is only 1.46% near the extreme load, and the minimum error of short-circuit current and in-ring current obtained by the semi-physical simulation platform can be controlled to 2.45% and 4.11%, respectively, and the range of transient peak coefficient error is in the range of [-1.66%,1.39%]. The application of the semi-physical simulation platform for measuring grid short-circuit parameters has high accuracy and guides optimizing grid configuration.