Power Swing Detection via Local Impedance Estimation
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Solution Overview
Problem
Conventional power system protection methods struggle to selectively and reliably detect power swings and isolate generators due to reliance on preliminary settings that do not adapt to system configuration changes or real-time dynamics, often requiring costly high-speed communication networks and approximating swing center voltage estimation.
Innovation Solution
A method and device that utilize local measurements of voltage and current phasors from source-end generators to estimate transmission and receiving-end impedances, calculate the swing angle between internal voltages, and detect power swings based on these parameters, allowing for real-time detection and isolation of generators during unstable conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional impedance-based protection approaches are used with preliminary settings, then relay operation can be simplified, but the protection device becomes unable to selectively and reliably detect power swings when system configuration changes occur
Solution Approach 1:
The patent implements dynamic adaptation of protection settings by continuously estimating swing center voltage and calculating impedance values in real-time based on current system conditions. The relay dynamically adjusts its detection parameters according to actual power system dynamics rather than relying on fixed preliminary settings, ensuring reliable operation during configuration changes.
Solution Approach 2:
The system uses feedback from real-time measurements of voltage and current to continuously update the swing center voltage estimation and impedance calculations. This feedback mechanism allows the protection device to adapt to system changes and maintain reliable power swing detection throughout operational phases.
2Measurement precision
If high-speed communication networks such as fiber optic or GPS are used to obtain data from remote generators for swing center voltage estimation, then detection accuracy can be improved, but implementation and maintenance costs increase significantly
Solution Approach 1:
The patent enables each local relay to independently estimate the swing center voltage using only local measurements of voltage and current at its own location. The relay calculates the impedance angle and determines swing center voltage without requiring data from remote generators or external communication networks, making the system self-sufficient and eliminating complex infrastructure requirements.
Solution Approach 2:
The patent uses locally measured voltage and current phasors as intermediaries to indirectly determine the swing center voltage. Instead of directly measuring or communicating remote generator data, the system uses local electrical parameters as mediators to calculate the swing center voltage through impedance angle relationships, achieving accurate estimation without complex communication networks.
3Ease of manufacture
If approximate estimation methods are used for swing center voltage, then implementation can be simplified, but real-time power system dynamics are not taken into consideration reducing detection accuracy
Solution Approach 1:
The patent changes the approach from using fixed approximate values to dynamically calculating impedance parameters (magnitude and angle) based on real-time voltage and current measurements. The system continuously updates the impedance angle to reflect current system conditions, enabling accurate swing center voltage estimation that adapts to real-time power system dynamics while maintaining implementation simplicity.
Data Source
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AI summary
A method (400) includes obtaining a voltage phasor (402), a current phasor (404) and a mechanical rotor angle (405) of a source end generator. A receiving end generator impedance and a line impedance between the source end generator and a receiving end generator is also estimated (406). Furthermore, a swing angle between an internal voltage of the source end generator and an internal voltage of the receiving end generator as a function of obtained voltage phasor, current phasor, mechanical rotor angle and the impedances is estimated (408). A power swing condition is then determined (410) based on the estimated swing angle.