Transformer Inrush Current Control via Phase-Angle Switching
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Solution Overview
Problem
Existing methods for reducing transformer inrush currents during energization in three-phase power grids are either complex, require additional components, or are limited to specific transformer configurations, lacking a universal solution that effectively addresses high inrush currents across all transformer configurations.
Innovation Solution
A method for Point-on-Wave-Switching (PoWS) that determines the switching instants for each phase of a transformer based on its mechanical construction properties, including vector groups and core types, to minimize inrush currents by calculating phase angles and time delays for controlled asynchronous switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If controlled switching (Point-on-Wave-Switching) is applied to reduce transformer inrush currents, then inrush current magnitude is reduced, but the complexity of determining switching instants increases
Solution Approach 1:
The patent applies parameter changes by determining the voltage phase angle at the switching instant and using it to calculate the optimal switching time. The switching instant is determined based on the phase angle of the voltage signal, which changes continuously, allowing the system to select the optimal moment for switching that minimizes inrush current while maintaining a relatively simple determination process.
2Object-generated harmful factors
If demagnetization or damping elements are applied to mitigate inrush currents, then inrush currents are reduced, but additional components must be installed in the primary power system
Solution Approach 1:
The patent extracts the inrush current mitigation function from the physical hardware domain and implements it through control logic and calculation methods. Instead of adding demagnetization circuits or damping elements to the power system, the solution uses computational determination of switching instants based on voltage phase angle, removing the need for additional physical components while achieving the same protective effect.
3Device complexity
If sequential phase energization is used to avoid additional components, then device complexity is reduced, but the method is limited to specific transformer configurations
Solution Approach 1:
The patent achieves universality by developing a switching instant determination method that works for all transformer configurations. The approach uses the voltage phase angle parameter, which is independent of transformer type, to determine optimal switching instants. This makes the method universally applicable to different transformer configurations without requiring additional components or modification of the basic approach.
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 reduces magnetic flux rapidly and accurately determines switching instants for each transformer configuration, minimizing inrush currents to values close to nominal steady-state magnetizing currents, thereby enhancing power system reliability and avoiding transformer damage.
Implementation Method 1
The intensity of a magnetizing inrush depends mainly on the remanent magnetic flux of the energized transformer
Data Source
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AI summary
The invention relates to a method for energizing a transformer (11) in a three-phase power grid (10), wherein the phases (L1, L2, L3) of the transformer (11) are switched-on asynchronously in a manner to reduce inrush-currents flowing in the power grid (10). To avoid high inrush currents with any possible transformer configuration, the following steps are performed: - determining a remanent magnetic flux in the respective phases (L1, L2, L3) of the transformer (11); - determining a sequence for switching-on the respective phases of the transformer (11), wherein the sequence depends on mechanical construction properties of the transformer (11) ; - calculating a phase angle of an electric voltage at which at least one phase is to be switched-on first; - calculating, for the remaining phases, a respective time delay after switching-on of the at least one first phase; and - generating switching signals to switch-on the at least one first phase at the determined phase angle of the electric voltage signal and to switch-on the remaining phases at the time defined by the determined respective time-delay. The invention is also related to a corresponding device and system to perform such a method.