Controlled Switching Device for Transformer Inrush Current Mitigation
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Solution Overview
Problem
Existing methods for mitigating inrush currents during power transformer energization, such as those using pre-insertion resistors or smoothing inductors, are complex and costly, and existing controlled switching techniques are limited to specific transformer configurations and magnetic flux patterns, failing to effectively address inrush currents in all scenarios, particularly for three-phase circuit breakers with simultaneous pole operation.
Innovation Solution
A controlled switching device that calculates the optimal electrical switching angle of a circuit breaker based on residual magnetic fluxes from each transformer phase, allowing simultaneous or independent pole operation to synchronize the closing of all phases at an optimal angle, reducing inrush currents by matching the prospective magnetic flux with the residual flux during transformer energization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pre-insertion resistors or smoothing inductors are used to mitigate inrush current, then inrush current is reduced, but device complexity and installation cost increase
Solution Approach 1:
The invention extracts and removes the pre-insertion resistors and smoothing inductors from the circuit breaker system. Instead of using these additional components, the patent employs a control system that calculates the optimal switching angle based on residual magnetic flux measurements, thereby eliminating the need for complex mechanical add-ons while still mitigating inrush current effectively
Solution Approach 2:
The invention replaces the mechanical approach of using physical resistors and inductors with an electrical control approach. By using a control system that measures residual magnetic flux and calculates the optimal switching angle, the patent substitutes mechanical component-based current mitigation with an intelligent control strategy that achieves the same goal without additional hardware
2Object-affected harmful factors
If pre-insertion resistors or smoothing inductors are used to mitigate inrush current, then inrush current is reduced, but maintenance frequency increases and reliability decreases
Solution Approach 1:
The invention enables the circuit breaker system to serve itself by incorporating a control system that autonomously measures residual magnetic flux, calculates the optimal switching angle, and executes the switching operation without requiring external intervention or additional maintenance-prone components. This self-service approach eliminates the need for maintaining pre-insertion resistors and smoothing inductors
Solution Approach 2:
By removing the pre-insertion resistors and smoothing inductors from the system, the invention eliminates the maintenance operations associated with these components. The control system approach requires no physical wear parts or additional maintenance, thereby improving overall system reliability and reducing maintenance frequency
3Object-affected harmful factors
If controlled switching is used with specific residual magnetic flux patterns, then inrush current is mitigated, but adaptability to different transformer configurations is limited
Solution Approach 1:
The invention creates a universal controlled switching system that can adapt to any transformer configuration (Y-Δ, Y-Y, Δ-Δ, Δ-Y connections) and any residual magnetic flux pattern. The control system measures the actual residual flux in each phase and calculates the optimal switching angle dynamically, making the system versatile and applicable to all transformer types without requiring specific flux patterns or configurations
Solution Approach 2:
The invention employs a dynamic control strategy where the optimal switching angle is calculated in real-time based on the measured residual magnetic flux. This dynamic approach allows the system to adapt to any transformer configuration and flux pattern, rather than relying on fixed or predetermined switching angles that would be limited to specific configurations
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 mitigates inrush currents across various transformer configurations, including Y-Δ, Y-Y, Δ-Δ, and Δ-Y connections, by determining the optimal closing angle for the circuit breaker, thereby reducing stress on equipment and improving power system reliability without the need for additional components.
Implementation Method 1
calculates the residual magnetic fluxes inside the transformer core by integrating the transformer voltage
Implementation Method 2
synchronize the closing of all phases at an optimal angle, reducing inrush currents by matching the prospective magnetic flux with the residual flux
Data Source
AI summary
This invention describes a method and an electrical circuit for controlling the closing of a three-phase circuit breaker with simultaneous pole operation to mitigate the inrush current resulting from power transformer energization by taking into account the residual magnetic flux in the transformer's magnetic core. It is disclosed a method to perform controlled switching on transformer and therefore mitigate the inrush current. It is disclosed that this method can be applied to any configuration of transformers which can be, but not limited to, Y-Δ, Y-Y, Δ-Δ and Δ-Y with either floating or grounded neutral.