Outline Introduction to Synchrophasors Measuring Synchrophasors - PowerPoint PPT Presentation

Phasor Measurement Unit and Applications ¡ ¡ ¡ ¡ Akanksha Pachpinde ¡

Outline Introduction to Synchrophasors § Measuring Synchrophasors using PMU § Terms associated with PMU § PMU architecture § Applications of PMU § Monitoring § Protection § Control ¡ §

Introduction to Synchrophasors An AC waveform can be mathematically represented as: In phasor notation it can be represented as: where : ¡ ¡ = ¡rms ¡magnitude ¡of ¡waveform ¡ ¡ = ¡phase ¡angle ¡

Measuring Synchrophasors using PMU Anti aliasing filter – restricts bandwidth of signal to satisfy sampling • theorem GPS time tagging – provides a time stamp for the signal • Phase locked oscillator – keeps frequency of the reference and measured • signal equal

Terms associated with PMU • Time tagging: – 8 bit message – 4 bits SOC, 3 bits fraction of second, 1 bit quality Synchronized reporting: • – Reporting rate must evenly divide 1 second interval (IEEE standard) Total Vector Error: • where X r and X i represent theoretical synchrophasor and X r (t 0 ) and X i (t 0 ) represent measured values

Example of PMU Architecture

PMU applications - Monitoring 1. Digital System Disturbance Recorder: First recorded wide are measurements in 1992 § After 1996 and 2003 blackouts EIPP formed (now known as NASPI) § Low frequency oscillation detection and oscillation source detection § Phase angle difference and voltage stability detection § Post mortem analysis § High cost led to development of concepts such as depth of § observability 2. For State Estimation: Prior state only estimated from power flow measurements § Using synchrophasors state can be measured as complex bus voltages § can be measured No longer have to assume that the system is static during the scan §

PMU applications – Protection and Control Control of Backup Relay performance False tripping of relays might occur during system § disturbances PMUs can be used for supervisory control of § distance relays to overcome this problem Adaptive out-of-step protection Out-of-step relays used to determine if the § generators are going out of step Become outdated quickly in a highly § interconnected network Wide-area measurements of positive sequence § voltages and swing angles can directly determine stability

PMU applications – Protection and Control Security- dependability § Failure modes of relay- trips when it should not or fails to trip when it should § False trips can aggravate disturbances in a highly stressed system § Supervisory control can ensure that more than one relay sees a fault before breaker is actuated Improved control § Control can be based on measurement values of remote quantities § System can react to threatening situations with employing continuous feedback control § Addition of PMU controllers to local controllers will add robustness ¡ ¡

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