Power Swing Detection via Dynamic Swing Angle Estimation
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Solution Overview
Problem
Conventional power system relaying approaches struggle to selectively and reliably detect power swings due to their reliance on extensive stability studies and lack of real-time dynamic adaptation, often resulting in inadequate protection and potential equipment damage during power system disturbances.
Innovation Solution
A method and device that estimate the swing angle between internal voltages of source-end and receiving-end generators using local measurements of voltage and current phasors, mechanical rotor angles, and impedance calculations, enabling real-time detection of power swings and triggering protective measures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional impedance-based protection approaches (PSB and OST) are used, then relay operation can be implemented, but the protection device cannot selectively and reliably detect power swings due to lack of real-time dynamic adaptation
Solution Approach 1:
The patent implements dynamic estimation of swing center voltage using real-time measurements of voltage phasors, current phasors, and mechanical rotor angles. The swing angle is continuously calculated as θ = δ - α, where δ is the mechanical rotor angle and α is the estimated swing center angle derived from terminal voltage and current measurements. This dynamic calculation allows the protection device to adapt to varying system configurations and operational conditions in real-time, resolving the contradiction between reliability and adaptability.
2Reliability
If extensive power system stability study is conducted for preliminary settings, then optimal relay settings can be obtained, but the protection device becomes unable to accommodate dynamic changes in system configuration
Solution Approach 1:
The patent employs feedback mechanisms by continuously measuring terminal voltage phasors (Vt), current phasors (It), and mechanical rotor angles (δ), then using these measurements to dynamically estimate the swing center voltage and calculate the swing angle. This closed-loop feedback system automatically adjusts protection settings based on real-time system conditions, eliminating the need for extensive preliminary stability studies and enabling immediate adaptation to configuration changes.
3Measurement precision
If high-speed communication network is used for SCV estimation, then accurate power swing detection can be achieved, but economic challenges arise due to implementation and maintenance costs
Solution Approach 1:
The patent enables the source-end generator to perform self-service by using its own local measurements (voltage phasor Vt, current phasor It, and mechanical rotor angle δ) to estimate the swing center voltage and detect power swings. This eliminates the need for high-speed communication networks to transmit data from receiving-end generators, as the swing angle calculation is performed locally using available measurements and the relationship θ = δ - α.
4Measurement precision
If direct rotor angle measurement is used, then accurate power swing detection is achieved, but in the absence of direct measurements it becomes difficult to determine power swing condition
Solution Approach 1:
The patent uses the terminal voltage phasor (Vt) and current phasor (It) as intermediary measurements to estimate the swing center voltage and indirectly determine the swing angle. The mechanical rotor angle (δ) serves as another intermediary that, when combined with the estimated swing center angle (α), provides the swing angle (θ = δ - α). This approach enables accurate power swing detection without requiring direct swing angle measurement instruments.
Data Source
AI summary
A method includes obtaining a voltage phasor, a current phasor and a mechanical rotor angle 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. 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. A power swing condition is then determined based on the estimated swing angle.