Phase Controlled Transformer Energizing Reduces Inrush Current
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Solution Overview
Problem
Inrush currents in power transformers can cause damage due to their high magnitude, and existing methods to reduce them are ineffective because they rely on accurate estimation of residual flux, which is challenging due to its dependence on de-energization conditions and changes over time.
Innovation Solution
A method for phase-controlled energizing of power transformers using a controller that acquires electrical voltage signals, determines characterizing data before and after de-energization, estimates the magnetization level, and operates the circuit breaker at a determined instant to minimize inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If controlled de-energization followed by controlled energization is used to reduce inrush current, then inrush current is reduced to certain extent, but the method requires accurate estimation of residual flux which is challenging and may not be effective when residual flux level changes
Solution Approach 1:
The system performs preliminary characterization of the voltage signal to determine the actual residual flux level before energization. By analyzing the voltage signal during a pre-determined set of cycles after de-energization, the system determines characterizing data that represents the residual flux level, enabling accurate phase angle selection for energization that accounts for the actual residual flux condition
Solution Approach 2:
The system uses feedback from the voltage signal characterization to adjust the energization strategy. The controller continuously monitors the voltage signal, determines characterizing data, and uses this information to select the appropriate phase angle for energization, creating a closed-loop control system that adapts to the actual residual flux level
2Object-generated harmful factors
If residual flux estimation method is used, then inrush current reduction depends on effective estimation of residual flux, but residual flux magnitude changes with time due to magnetic properties, environment, and connected components
Solution Approach 1:
The system performs preliminary characterization of the voltage signal to determine the actual residual flux level before energization. By analyzing the voltage signal during a pre-determined set of cycles after de-energization, the system determines characterizing data that represents the residual flux level, enabling accurate phase angle selection for energization that accounts for the actual residual flux condition
Solution Approach 2:
The system dynamically adapts the energization strategy based on the actual residual flux level. Instead of using fixed assumptions about residual flux, the controller continuously characterizes the voltage signal and adjusts the energization phase angle accordingly, making the system responsive to changes in residual flux magnitude over time
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 effectively reduces inrush currents by accurately determining the switching instant based on magnetization levels, thereby minimizing electrical disturbances and damage to power systems.
Implementation Method 1
acquiring electrical voltage signal from a voltage sensing device connected to the power transformer
Data Source
AI summary
A method for phase controlled energizing of a power transformer includes acquiring electrical voltage signal from a voltage sensing device connected to the power transformer. Determining a first characterizing data in the voltage signal within a pre-determined set of cycles at about an opening operation of a circuit breaker and determining a second characterizing data within the pre-determined set of cycles in the voltage signal subsequent to the opening operation of the circuit breaker. Estimating a level of magnetization of the core of the power transformer based on at least one of second characterizing data, and the first characterizing data and the second characterizing data. Operating the circuit breaker at a determined instant of switching based on the estimated level of magnetization for a phase controlled energizing of the power transformer by the circuit breaker.