Transmission Line Source Impedance Estimation From Switching Events
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Solution Overview
Problem
Existing methods for estimating source impedances in power transmission systems are limited, as they often require creating faults, can only determine magnitude, and do not account for angles, making them inadequate for protection functions where phase information is crucial, and they rely on data that may not be readily available at the substation level.
Innovation Solution
A method that uses voltage and current measurements, along with status signals, to estimate source impedances across transmission lines by detecting events such as faults or shunt injections, calculating bus and line impedances, and applying correction factors to determine complex impedance values, eliminating the need for fault creation and incorporating substation-level data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fault creation methods are used to estimate source impedance magnitude, then measurement data becomes available, but the method becomes unsafe and operationally disruptive
Solution Approach 1:
The patent converts naturally occurring faults (which were previously harmful disruptions) into beneficial measurement opportunities. By detecting and utilizing fault events that occur in the power system, the method extracts useful source impedance information without requiring intentional fault creation, thus converting operational harm into measurement benefit
Solution Approach 2:
The system uses its own operational data (voltage and current measurements during normal and fault conditions) to estimate source impedance. The power system itself provides the measurement data needed through its normal operation and naturally occurring events, eliminating the need for external test equipment or intentional disruptions
2Measurement precision
If traditional methods are used to estimate source impedance, then magnitude can be determined, but angle information is lost which is crucial for protection functions
Solution Approach 1:
The patent separates the estimation process into distinct phases: normal operation data collection and fault condition data collection. By segmenting the measurement process, the system can use normal operation for baseline data and fault events for accurate complex impedance determination, ensuring both magnitude and angle are captured without contamination from transient effects
Solution Approach 2:
The system exploits changes in system parameters (voltage and current magnitudes and phases) that occur during fault events. These parameter changes provide the additional information needed to calculate both the real and imaginary components of source impedance, transforming a magnitude-only measurement problem into a complex impedance estimation problem
3Measurement precision
If network topology information is required for source impedance calculation, then accurate results can be obtained, but the method becomes impractical at substation level where topology data is unavailable
Solution Approach 1:
The patent extracts the essential measurement data (voltage and current at the substation) needed for source impedance estimation, separating it from the unnecessary network topology information. By taking out only the critical local measurements and eliminating the need for complete system topology data, the method becomes implementable at the substation level while maintaining accuracy
Solution Approach 2:
The patent uses fault event data as an intermediary to bridge the gap between limited local measurements and accurate source impedance determination. The fault event serves as a mediator that provides additional system response information, enabling accurate impedance calculation without requiring direct knowledge of the complete network topology
Data Source
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AI summary
The present invention relates to estimating source impedances across one or more transmission lines connecting at least two substations. Each substation is associated with an equivalent source having a respective source impedance. Voltage and current measurements and status signals are obtained. The voltage and current measurements provide terminal or bus voltages and line currents at each terminal, and the status signals are associated with switching events at the one or more transmission lines or at the substations. An event associated with a disturbance or current injection is detected from one or more of the obtained measurements and the obtained status signals. The source impedance of each equivalent source is estimated based on the event, using line parameters and the voltage and current measurements associated with the event.