A method for identifying transformers and inrush currents based on site domain information of smart substations

Abstract

Disclosed is a method for identifying transformer sympathetic inrush current based on intelligent substation territory information. The method includes the following steps: (1) judging whether a transformer is in a no-load shutdown state, (2) judging whether the phenomenon of no-load transformer switching-in exists, (3) acquiring line current of the switching-in side of the transformer which is switched in without load, acquiring line current of primary and secondary sides of other operating transformers, and calculating differential current of the primary and secondary sides of the operating transformers, (4) continuously calculating the secondary harmonic component of the operating transformers and carrying out timing from the moment of no-load switching-in till the secondary harmonic component is larger than m% and fundamental waves exceed by n% of rated current, (5) comparing the secondary harmonic phase of the switched-in transformer and the secondary harmonic phase of operating transformers, and (6) increasing the constant value of differential protection starting current of the operating transformers to k1 times of an original starting value and carrying out timing, and setting the constant value to be the original starting value and returning the process to the step (1) when one of three conditions is met. According to the method for identifying the transformer sympathetic inrush current based on the intelligent substation territory information, during the sympathetic inrush current, protection can still be effectively carried out when internal fault of the transformers occurs; after the sympathetic inrush current, differential protection action characteristics can return to original action states quickly.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a method for identifying transformers and inrush currents by using station domain information of intelligent substations, which can be used to prevent maloperation of differential protection of transformers in intelligent substations due to inrush currents. Background technique [0002] Transformer is an important electrical equipment in the power system, and its safe operation affects the safety and stability of the power system. Differential protection has been used for a long time as the main protection of transformer protection. Its advantages are fast action speed and good selectivity. However, due to the influence of external factors and protection principles, its correct action rate is not high. It has been reported many times that the transformer is switched on without load, which causes the adjacent running transformer to genera...

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Problems solved by technology

Disconnecting the neutral point of the operating transformer cannot avoid the generation of inrush current; choosing a current transformer with better performance increases the operating cost; the braking criterion of the zero-sequence second harmonic component is only applicable to the grounding of the operating transformer neutral point However, its effectiveness still needs to be verified; strengthening the second harmonic blocking criterion may cause false blocking of the protection under fault conditions; the effectiveness of the time difference method still needs to be tested in actual operation

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