Transformer Switching Angles for Inrush Current Reduction
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Solution Overview
Problem
Existing methods for minimizing transformer inrush current are complex and require significant engineering efforts due to uncertainties in estimating remanent flux and site-specific parameters, especially in medium voltage circuit breakers.
Innovation Solution
Determine suitable closing angles for different system configurations and store them in a database, using a monitoring system to identify a reference angle and operate the switching device at predetermined opening and closing angles based on load conditions, eliminating the need for remanent flux estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage sensors are installed downstream of the circuit breaker to integrate voltage with respect to time for estimating remanent flux, then the optimal closing angle can be determined, but the device complexity and engineering efforts increase significantly
Solution Approach 1:
The patent extracts the remanent flux estimation problem from the complex measurement system and replaces it with a database lookup approach. Instead of using voltage sensors downstream to integrate and estimate remanent flux, the system uses pre-calculated optimal closing angles stored in a database, which are retrieved based on system configuration parameters, thereby eliminating the need for complex real-time flux estimation hardware and software
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing optimal closing angles for different system configurations in a database before actual operation. This allows the system to quickly retrieve pre-determined optimal angles without performing complex real-time calculations or measurements, significantly reducing device complexity while maintaining measurement precision
2Object-affected harmful factors
If site-specific simulations are performed to find the optimal phase angle, then the transformer inrush current can be minimized, but the engineering efforts and time required increase significantly
Solution Approach 1:
The patent performs the complex simulation work in advance by pre-calculating optimal closing angles for various system configurations and storing them in a database. During actual circuit breaker installation and operation, the system simply retrieves the pre-computed optimal angle from the database based on the specific configuration, eliminating the need for time-consuming site-specific simulations while still achieving inrush current minimization
Solution Approach 2:
The patent creates a database that serves as a copy of simulation results for different system configurations. Instead of performing original simulations at each site, the system uses pre-generated simulation data stored in the database, significantly reducing engineering time and effort while maintaining the accuracy of inrush current minimization
3Object-affected harmful factors
If the optimal closing angle is determined based on remanent flux estimation, then the transformer inrush current is reduced, but the reliability decreases due to uncertainties in flux estimation
Solution Approach 1:
The patent implements a feedback mechanism where the system determines the actual system configuration (such as load conditions and equipment connections), uses this information to query the database for the corresponding optimal closing angle, and then applies this angle for circuit breaker operation. This closed-loop approach ensures that the optimal angle always corresponds to the actual system state, improving reliability by eliminating uncertainties associated with real-time flux estimation
Data Source
AI summary
A method of operating a switching device in a system. The method includes monitoring a voltage; operating the system at each of a plurality of system configurations; and, for each of the system configurations and a predetermined same opening angle relative to a reference angle of the monitored voltage, determining a suitable closing angle relative to the reference angle and storing information about the determined suitable closing angle in association with the system configuration in a database. The method then includes, determining a system configuration in the system; at the predetermined same opening angle, opening the switching device; from the database, obtaining a closing angle of the determined suitable closing angles, wherein the system configuration with which the obtained closing angle is associated in the database corresponds to the determined system configuration; and at the obtained closing angle, closing the switching device.