Phase Control Switching Device for Transformer Inrush Current Reduction
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Solution Overview
Problem
Conventional phase control switching devices fail to minimize transient exciting currents in transformers due to differences in residual magnetic flux between phases during breaker operations, leading to magnetic saturation and excessive current surges.
Innovation Solution
A phase control switching device that synchronizes breaker operations with voltage zero points across phases, ensuring equal residual magnetic flux levels between phases at the time of switching, thereby minimizing the difference in residual magnetic flux and preventing magnetic saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If breaking is carried out at a current zero point which occurs at an interval of an electrical degree of 60° in commercial frequency every phase, then the breaking operation is simple and standardized, but the residual magnetic flux of the second throwing phase or third throwing phase becomes unequal to the first breaking phase, causing transitional phenomenon and DC magnetic flux superposition
Solution Approach 1:
The invention applies preliminary action by estimating the residual magnetic flux of each phase before the throwing operation and using this information to determine the optimal throwing sequence and timing. The phase control switching operation processor calculates the residual magnetic flux based on voltage waveforms and uses this preliminary knowledge to plan the throwing sequence that will minimize transient exciting incoming current.
Solution Approach 2:
The invention applies dynamics by making the breaking phase selection dynamic rather than fixed. Instead of always breaking at the same electrical degree interval (60°), the system dynamically selects which phase to break first based on the actual residual magnetic flux conditions of each phase, allowing adaptive optimization of the throwing sequence to achieve equal residual magnetic flux levels.
2Manufacturing precision
If the closing operation is controlled in consideration of the residual magnetic flux of each phase, then the throwing timing can be optimized, but there remains a difference in residual magnetic flux value between the second throwing phase and the third throwing phase, causing transitional phenomenon and magnetic saturation
Solution Approach 1:
The invention applies feedback by continuously monitoring the voltage waveforms of each phase and using this information to estimate the residual magnetic flux levels. The phase control switching operation processor uses this feedback to adjust the throwing sequence and timing, ensuring that the residual magnetic flux levels are equalized before the throwing operation, thereby preventing transitional phenomenon and magnetic saturation.
Solution Approach 2:
The invention applies parameter changes by modifying the throwing sequence and timing parameters based on the measured voltage waveforms and estimated residual magnetic flux levels. Instead of using fixed throwing intervals, the system changes the throwing parameters dynamically to achieve equal residual magnetic flux levels across all phases, eliminating the harmful transitional effects.
3Productivity
If the breaker is thrown at an electrical degree at which the residual magnetic flux and the stationary magnetic flux are not coincident, then the switching operation can be performed, but a transitional phenomenon of magnetic flux occurs and DC magnetic flux is superposed, causing severe transitional exciting incoming current
Solution Approach 1:
The invention applies preliminary action by estimating the residual magnetic flux of each phase before the throwing operation and using this information to determine the optimal throwing sequence and timing. The phase control switching operation processor calculates the residual magnetic flux based on voltage waveforms and uses this preliminary knowledge to plan the throwing sequence that will minimize transient exciting incoming current.
Solution Approach 2:
The invention applies parameter changes by modifying the throwing sequence and timing parameters based on the measured voltage waveforms and estimated residual magnetic flux levels. Instead of using fixed throwing intervals, the system changes the throwing parameters dynamically to achieve equal residual magnetic flux levels across all phases, eliminating the harmful transitional effects.
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
The solution effectively suppresses transitional exciting currents by ensuring symmetrical magnetic flux conditions during breaker operations, reducing the risk of magnetic saturation and minimizing harmful current surges in transformers.
Implementation Method 1
a voltage measuring unit for measuring the voltages at the transforming unit side and the power system side of the breaker of each phase
Implementation Method 2
a phase control switching operation processor for carrying out switching operation of the breaker of each phase in consideration of the residual magnetic flux of the transforming unit
Implementation Method 3
a breaker of each phase, which is connected to the transforming unit and opened to break failure current and load current of the transforming unit and thrown to excite the transforming unit
Data Source
AI summary
Respective contact terminals in respective arc-suppressing spaces of respective breakers are opened at a voltage zero point of any phase of three phases, simultaneously among the three phases. If current breaking is carried out for the three phases at the same time, when the breakers of the three phases are opened, the residual magnetic levels of the respective phases of a transformer can be controlled so that the residual magnetic flux level of the phase opened at the voltage zero point is maximum (for example, −2K or +2K) and the residual magnetic flux level of the other two phases are opposite in polarity to the residual magnetic flux level of the phase concerned and equal to substantially the same residual magnetic flux (for example, +K and +K or −K and −K) which is equal to about one half of the residual magnetic flux level of the phase concerned. Accordingly, by throwing the phase broken at the voltage zero point at a first time, the difference in residual magnetic flux between the second throwing phase and the third throwing phase just after the first phase is thrown can be substantially nullified.