Current Transformer Saturation Prediction via Dual-Side Current Analysis
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Solution Overview
Problem
Current power substation automation systems lack measures to prevent differential protection mal-operation caused by current transformer saturation during sympathetic inrush, leading to unreliable operation.
Innovation Solution
A method for predicting current transformer saturation by detecting current outputs from both high and low voltage sides, calculating fundamental vectors and DC components, and generating a prediction signal based on saturation judgment conditions to prevent differential protection mal-operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current transformers are used for differential protection of the transformer, then the transformer protection function is realized, but the current transformer may saturate under sympathetic inrush causing protection mal-operation
Solution Approach 1:
The patent applies preliminary action by detecting early signs of current transformer saturation (such as DC component ratio and fundamental vector angle difference) before the saturation fully develops and causes differential protection mal-operation. The system generates a prediction signal when saturation conditions are detected, enabling preventive action to be taken before the harmful effect occurs.
Solution Approach 2:
The patent introduces an intermediary detection and prediction mechanism that monitors current transformer operating conditions (DC component, fundamental vector, angle difference) and generates prediction signals. This intermediary system acts as a mediator between the current transformer and the differential protection, preventing the harmful saturation effect from triggering false protection operations.
2Measurement precision
If current transformer saturation is detected by monitoring differential current, then saturation can be identified, but false differential protection operations may still occur during deep saturation
Solution Approach 1:
The patent introduces an intermediary prediction mechanism that monitors early saturation indicators (DC component ratio, fundamental vector angle difference) before deep saturation occurs. This intermediary system generates prediction signals that prevent false differential protection operations, acting as a mediator between the current transformer and the protection system to eliminate mal-operation during deep saturation.
Solution Approach 2:
The system performs preliminary detection of saturation conditions by calculating DC component ratios and fundamental vector angle differences before the saturation deepens to dangerous levels. By taking preliminary action when early saturation signs are detected, the system prevents the progression to deep saturation that would cause false protection operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively predicts current transformer saturation, preventing differential protection mal-operation and enhancing the reliability of power system operations.
Implementation Method 1
a first current transformer is connected to a high voltage side of a transformer and a second current transformer is connected to a low voltage side of the transformer
Implementation Method 2
After the current transformer at one side is saturated, its inductance would be decreased, which may cause decreasing in an impendence angle of this current transformer
Data Source
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AI summary
There is provided a method for predicting a current transformer saturation, comprising: detecting a first current from a first current transformer at a high voltage side of a transformer and detecting a second current from a second current transformer at a low voltage side of the transformer; calculating a first fundamental vector, a first DC component and a first total RMS of the first current, and calculating a second fundamental vector, a second DC component and a second total RMS of the second current; and generating a prediction signal for the current transformer saturation according to the first fundamental vector, the first DC component, the first total RMS, the second fundamental vector, the second DC component and the second total RMS. The current transformer saturation may be predicted effectively before it triggers a differential protection of the transformer, thus a differential protection mal-operation of the transformer may be avoided.