Railway Transformer Inrush Current Reduction
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Solution Overview
Problem
High inrush currents in railway transformers due to magnetic remanence cause potential damage, protective relay misoperation, and reduced power quality, as existing methods struggle to precisely control the energization timing to prevent core saturation.
Innovation Solution
Measuring and calculating the magnetic remanence in transformers, and connecting the voltage supply at or near a peak voltage if remanence is negative or positive to achieve symmetric magnetization, thereby reducing the risk of saturation and inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transformer is energized at an arbitrary point in time, then the system can be energized quickly, but the magnetic remanence causes core saturation and high inrush currents
Solution Approach 1:
The system performs preliminary measurement of magnetic remanence before energization and calculates the optimal energization timing in advance. By determining the remanence value and predicting the induced flux trajectory beforehand, the system can select the precise moment to close the breaker that avoids core saturation, thus enabling both quick energization and reliable operation.
Solution Approach 2:
The system measures the actual magnetic remanence in the transformer core before energization and uses this feedback information to adjust the energization timing. The control unit calculates the induced flux based on the measured remanence and determines the optimal switching moment, creating a closed-loop control that adapts to the actual magnetic state of the transformer.
2Object-generated harmful factors
If the energization timing is precisely controlled to prevent core saturation, then inrush currents are reduced, but the control complexity increases
Solution Approach 1:
The system uses the transformer's own magnetic remanence characteristic to determine the optimal energization timing. By measuring the remanence that already exists in the core and calculating based on that, the system leverages the transformer's inherent properties rather than requiring external complex control mechanisms, thus reducing overall system complexity while effectively controlling inrush currents.
Solution Approach 2:
The system changes the timing parameter of energization based on the measured magnetic remanence value. Instead of using a fixed or arbitrary switching time, the control unit adjusts the energization moment as a variable parameter determined by the actual magnetic state, allowing adaptive control that simplifies the decision-making process while reducing inrush currents.
3Speed
If the breaker closes before the prospective flux equals the residual flux, then the system can respond quickly to load demands, but the remanence increases and saturation risk increases
Solution Approach 1:
The system replaces mechanical trial-and-error switching methods with electronic measurement and calculation. By using voltage integration to calculate induced flux and comparing it with measured remanence, the system electronically determines the precise optimal switching moment, substituting complex mechanical timing mechanisms with simpler electronic control that achieves both fast response and saturation prevention.
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
This approach significantly reduces the risk of transformer saturation and associated high inrush currents, ensuring stable power delivery and extending transformer lifespan by dissipating remanence rapidly.
Implementation Method 1
Transformer inrush currents are high magnitude currents generated when transformer cores are driven into saturation during energization
Implementation Method 2
A problem in connection with energization of the railway system is high inrush currents due to magnetic remanence in the transformers
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present invention relates to a method and an apparatus for reducing inrush currents in connection with energizing of transformers in a railway system. The railway system including a feeder (1) for supplying trains with alternating voltage, a plurality of transformers (3), and a breaker (5) configured to connect and disconnect the voltage supply to the trains and the transformers. The apparatus comprises a first measuring device (7) for measuring the voltage supplied to the breaker, a second measuring device (8) for measuring the voltage supplied from the breaker, means (12) for detecting when the breaker disconnects the voltage supply to transformers, calculating means (14) for calculating the magnetic remanence in the transformers upon detecting that the voltage supply has been disconnected and to determine whether the calculated magnetic remanence is positive or negative, and connecting means (16) for connecting the breaker upon energizing the railway system. The connecting means is configured to connect the breaker at a point in time on or close to a positive peak of the voltage supplied to the breaker if the magnetic remanence is negative, and to connect the breaker at a point in time on or close to a negative peak of the voltage supplied to the breaker if the magnetic remanence is positive.