Abb Power Td & Company

Abb Research Ltd.

Khoi Tien Vu

Damir Novosel

James Stoupis

David G Hart

Zhenyuan Wang

David Lubkeman

Murari M Saha

Ajay C Madwesh

Danny E Julian

Jan Ove Gjerde

Aftab Khan

Joe G Mazza

A substation intelligence system () includes a substation computer () which is operatively connected to a plurality of field devices () through an input/output subsystem (). Data indicative of the devices is stored in a substation database (). Advanced monitoring and/or diagnostics () use information from the database to perform various monitoring and/or diagnostic functions.

Electrical substation monitoring and diagnostics

A Voltage Instability Predictor (VIP) estimates the proximity of a power system to voltage collapse in real time. The VIP can be implemented in a microprocessor-based relay whose settings are changed adaptively to reflect system changes. Only local measurements (voltage and current) at the bus terminal are required. The VIP detects the proximity to collapse by monitoring the relationship between the apparent impedance {overscore (Z)},and the Th&eacute;venin-impedance. In addition, we disclose: (1) that the VIP may be used in connection with non-radial topologies; (2) a new, more robust method to track voltage collapse in terms of impedance using rolling sums; and (3) a new method for representing distance to voltage collapse in terms of power margins.

Applications and methods for voltage instability predictor (VIP)

A Voltage Instability Predictor (VIP) estimates the proximity of a power system to voltage collapse in real time. The VIP can be implemented in a microprocessor-based relay whose settings are changed adaptively to reflect system changes. Only local measurements (voltage and current) at the bus terminal are required. Contrary to the most common strategy to maintain voltage stability, which is to shed blocks of load when the voltage drops below a certain fixed threshold, which threshold is difficult to select since voltage magnitudes are a poor indicator of how close the system is to a collapse, the inventive VIP detects this proximity to collapse by monitoring the relationship between the apparent impedance {overscore (Z)},and the Thevenin-impedance circle.

Voltage instability predictor (VIP)&mdash;method and system for performing adaptive control to improve voltage stability in power systems

As a variation of the non-orthogonal filter, a phasor estimate is computed by using an N-point window. An aspect of the sub-window cosine filter is to repeat the basic cosine filter for only selected points of the window. In the end, a least-squares fit is used to obtain an estimate for the phasors components. Previous cosine techniques use a data window whose length is greater than 1 cycle while the present invention requires only 1 cycle.

Protective relay with improved, sub-window cosine filter

A method employed in a condition monitoring unit (CMU) for monitoring a circuit breaker or interrupter to obtain a substantially undistorted version of a waveform suffering from saturation distortion comprises employing a current transformer (CT) to measure a current waveform. The output of the CT is prone to be a partially distorted waveform. The invention is generic in the sense that it does not require parameters associated with the CT characteristics or with the burden impedance on the secondary side of the CT. A digital representation of the partially distorted waveform is obtained, and then undistorted portions of the partially distorted waveform are identified by comparing the amplitude of the partially distorted waveform within a sliding window to a pair of boundary values and identifying as undistorted those portions having an amplitude between the boundary values. Next, distorted portions of the waveform are separated from the undistorted portions, thereby yielding a data record with holes. Finally, a reconstructed waveform is formed by filling in the holes with data points representing an undistorted version of the observed waveform.

Growing community of inventors

Apex, NC, United States of America

Khoi Tien Vu