Abstract
Correct selection of relay protection settings of a power transformer ensures reliable trouble-free operation of both the step-down substation itself in the industrial power supply system, and consumers receiving power from it. Given the volume of necessary calculations that need to be performed both to determine the parameters of steady-state and emergency modes, and to calculate the settings of protections, the task of automating the process of performing these calculations is relevant. The authors of the article have developed an algorithm for automated calculation of the differential protection settings for a power transformer, which makes it possible to determine the settings of the specified protection, taking into account the microprocessor terminal's component base and the manufacturer's recommendations for protection devices, as well as the requirements for protection. The developed algorithm has been implemented as a software module for calculating setpoints as part of the KATRAN software and computing complex, which allows not only automated calculation of setpoints, but also preliminary calculations of normal operation, long-term current overload, as well as symmetrical and unsymmetrical short-circuit modes and complex unsymmetrical modes, i.e., emergency unsymmetry caused by a broken power line wire or a broken busbar in a distribution device, followed by a ground fault. This makes it possible to consider not only a two-phase short circuit behind the transformer as the minimum mode for assessing the sensitivity of the differential protection of the power transformer, but also a break in the busbars between the high-voltage inputs of the power transformer and the current transformers, followed by a phase-to-ground short circuit on the power transformer side.
Keywords
relay protection, power transformer, differential protection, short circuit, automated calculation
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