Prediction and detection method for current transformer saturation under sympathetic inrush current

Abstract

The invention provides a prediction method for current transformer saturation. The prediction method comprises the following steps: detecting a first current output from a high-voltage side current transformer of a transformer, and detecting a second current output from a low-voltage side current transformer of the transformer; calculating a first fundamental wave vector, a first DC (direct-current) component and a first total effective value of the first current, and calculating a second fundamental wave vector, a second DC component and a second total effective value of the second current; generating a current transformer saturation prediction signal according to the first fundamental wave vector, the first DC component, the first total effective value, the second fundamental wave vector, the second DC component and the second total effective value. By the method, the current transformer saturation can be predicted or detected effectively before the differential protection of the transformer caused by the current transformer saturation, so that the maloperation of the differential protection of the transformer can be effectively avoided.

Description

technical field [0001] The present invention relates to the relay protection of power plants and substation automation systems, and more particularly to a method for predicting and detecting saturation of a current transformer (CT) under surge current. Background technique [0002] In a power system there are often several transformers connected in parallel or in series. If at least one of these transformers is put into operation, there may sometimes be a summing inrush current between these transformers. [0003] Usually, a high-voltage side current transformer and a low-voltage side current transformer are respectively installed on the high-voltage side and low-voltage side of the transformer, and the differential protection of the transformer is realized through these two current transformers. Prolonged inrush current may cause saturation of high-voltage side or low-voltage side current transformers used for transformer differential protection, and then lead to different...

AI Technical Summary

Problems solved by technology

Eventually, when one side of the current transformer is deeply saturated and the other side of the current transformer is working normally, the differential current will be large enough to trigger the transformer differential protection, resulting in differential protection misoperation

[0005] At present, in some substation automation system products, for example, Schneider's Micom P40 platform products, no method is taken to prevent differential protection misoperation

Moreover, users often complain about the misoperation of differential protection.

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