Single-Pole Transformer Closing Control for Inrush Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for minimizing transformer inrush current in electrical three-phase systems face challenges due to uncertainties in estimating the remanent flux in the transformer core, requiring complex simulations and engineering efforts, and often fail to account for the magnetic state effectively.
Innovation Solution
A method involving a single-pole operated switching device that iteratively closes at different angles during start-up to determine a preferred closing angle based on inrush current analysis, eliminating the need for remanent flux estimation by monitoring voltage in one phase and selecting the angle resulting in reduced inrush current for future operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage sensors are installed downstream of the circuit breaker and voltage is integrated with respect to time to estimate remanent flux, then the optimal closing angle can be determined, but the device complexity and engineering effort increase significantly
Solution Approach 1:
The patent extracts the essential information needed for remanent flux estimation by using only the upstream voltage reference signal and inrush current measurement. It takes out the unnecessary downstream sensors and complex voltage integration system, keeping only the critical measurement elements (upstream voltage sensor and inrush current sensor) to determine the optimal closing angle.
Solution Approach 2:
The patent uses the upstream voltage reference signal as a proxy for the downstream voltage condition. Instead of directly measuring downstream voltage and integrating it, the system copies the reference angle information from the upstream side and combines it with inrush current measurements to infer the remanent flux state, avoiding the need for complex downstream sensing.
2Loss of energy
If site-specific simulations are performed to find the optimal phase angle, then the inrush current can be minimized, but significant engineering efforts and time are required for each installation
Solution Approach 1:
The system performs self-characterization by automatically measuring the inrush current at different closing angles during commissioning and determining the optimal angle through actual site performance rather than theoretical simulations. This self-service approach eliminates the need for extensive manual simulations and site-specific engineering analysis for each installation.
Solution Approach 2:
The patent implements a preliminary testing phase during commissioning where the circuit breaker is closed at multiple predetermined angles to map the inrush current characteristics. This preliminary action collects site-specific data that automatically establishes the optimal closing angle for that particular installation, avoiding the need for time-consuming simulations later.
3Ease of operation
If the circuit breaker is simultaneously operated for all phases, then the operation is simpler, but the inrush current cannot be effectively minimized due to ignoring phase-specific magnetic states
Solution Approach 1:
The patent segments the circuit breaker operation into phase-independent control, where each phase can be closed at its own optimal angle determined by its specific magnetic state and inrush current characteristics. This segmentation allows independent optimization of each phase's closing angle while maintaining a unified control system, balancing operational simplicity with inrush current minimization.
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 allows for effective reduction of transformer inrush current without estimating remanent flux, simplifying the process and ensuring consistent operation by selecting a closing angle that minimizes inrush current, thereby reducing wear and operational complexity.
Implementation Method 1
controlling that the opening and/or closing of electrical contacts occurs at a specific phase angle of a reference signal (voltage or current in the system)... to minimize transformer inrush current
Data Source
Figure 1~4
Figure 2A~2C
Figure 2D~2F
AI summary
A start-up method for reducing inrush current to a transformer (3) when closing a switching device (2). The switching device comprises three single-pole operated current interrupting means. The method comprises monitoring a voltage (U). The method comprises, for each of a sequence of iterations: at a same opening angle relative to a reference angle of the voltage, starting an opening sequence of the switching device; at a closing angle relative to the reference angle, which is shifted in relation to the closing angle of all other iterations in the sequence, starting a closing sequence of the switching device; and obtaining an indication of the overall inrush current resulting from the closing. The method comprises selecting for future use with said opening angle, the closing angle of one of the iterations in which the overall inrush current is relatively low when compared with the other iterations of the sequence.