Michael Vaiman

Calculation and Visualization of Power System Stability Margin Based on PMU Measurements

This paper introduces the concept of the Region Of Stability Existence (ROSE) and describes the framework for utilizing PMU data for computing of this region and operational margins. The approach presented in this paper is an automated process to continuously monitoring the transmission system in real-time environment by accurately calculating power system stability margins. Voltage constraints, thermal limits and steady-state stability are simultaneously monitored during the analysis. The region is shown on the planes of two phase angles and real powers. The paper also demonstrates the effect of remedial actions on the region. The approach is illustrated by using the ISO New Englands real-time model, SCADA data and PMU measurements. The study results show that this approach is effective in improving the reliability of the ISO New Englands transmission network and may be used for preventing major blackouts.

Prevention of cascading outages in Con Edison's network

This paper describes the framework for prevention of cascading outages caused by thermal overloads. The approach presented in this paper is a fast, flexible and automated process for assessment of cascading outages and their prevention. It helps to prevent the cascading outages by optimizing the existing available controls in the transmission network. Optimal remedial actions are applied first after the occurrence of an initiating event, and then at each cascading Tier, until the cascading event is mitigated. The paper also presents the ranking of cascading outages that is based on a minimum amount of load curtailment which is needed to alleviate the steady-state stability violations caused by cascading events. The approach was implemented using the Con Edisons 50,000-bus planning case. The study results show that this approach is very effective in improving the reliability of Con Edisons network and preventing major blackouts, caused by the cascading outages. The analysis may also be included as part of NERC-compliance studies. Con Edison is planning to extend the assessment of cascading outages by incorporating transient stability analysis.

Evaluate real-time system reliability using boundary-based concept for EKPC system

This paper addresses a comprehensive approach to evaluate reliability in a large transmission system for on-line and real-time environments. The paper also addresses the growing need for broader coordination between planning and operations. The paper describes how the boundary-based AC approach was utilized to evaluate the reliability of the EKPC network. The approach described in this paper offers a unique capability to automatically identify the boundary of the secure operating region for each contingency and rank contingencies in on-line and off-line environments. The study also shows how to optimize a transmission system using existing resources without building new transmission. The study was performed using the EKPC loadflow data to validate the proof of concept. It took under 20 minutes to perform AC contingency analysis on over 3,700 N-1 contingencies. The approach described in this paper will allow the operators to perform exhaustive analysis and determine the boundary of stability.

Implementation of ROSE for on-line voltage stability analysis at ISO New England

This paper describes the implementation of Region Of Stability Existence (ROSE) software at ISO-NE for on-line estimation of the power system transfer capability based on voltage and thermal limitations and for security monitoring. The software utilizes State Estimator (SE) and synchrophasor PMU data sets for determining the power system operational margin under normal and contingency conditions. ROSE implementation is based on “hybrid” approach where SE solution (model) is used to compute voltage stability limits, and PMU data (measurements) is used to determine the position of the current operating point. This software allows improving security of transmission system by continuously monitoring operational margin expressed in MW flow or in bus voltage angles, and alarming the operator if the margin violates a pre-defined threshold.

Implementation of ROSE for real-time voltage stability analysis at WECC RC

This paper describes the implementation of Region Of Stability Existence (ROSE) software at WECC-RCs operations centers for real-time voltage stability analysis. The software utilizes State Estimator (model) and synchorphasor (measurement) data sets for determining the power system operating margin under normal and contingency conditions. The framework presented in this paper allows for enhanced real-time situational awareness of system operators by continuously monitoring the transmission network utilizing the synchorphaor data, determining voltage stability limits using the State Estimator data, and alarming the operator if the current operating point approaches the limit. The paper discusses implementation of the ROSE application at Western Electricity Coordinating Council RC called WECC-ROSE.

Automated Critical Clearing Time calculation for analyzing faults at Entergy

This paper describes the implementation of Critical Clearing Time (CCT) software at Entergy for transient stability analysis. The software utilizes a fast time-domain simulation method to compute critical clearing time under different fault conditions. The framework presented in this paper allows for automated critical clearing time computations that eliminates manual time-consuming cut-and-try critical clearing time calculations. The paper discusses how automatic CCT computations are applied at Entergy for addressing various protection system concerns.

Practical experience in assessing the effects of extreme contingencies with respect to standards TPL-001-4 and CIP-014-1

This paper presents a comprehensive, practical approach to identify and analyze the effects of extreme contingencies that might lead to widespread power disruptions and cascading. Modern power systems are normally designed to withstand n-1 and credible n-2 outages. The ability of a system to survive extreme contingencies and major disturbances has not been comprehensively addressed by system planners in the past. Extreme outages are a result of either cyber or physical threats. Both types of events expose transmission planners and operation engineers to new challenges, including identifying how to minimize their impact on system vulnerability. The suggested approach is to further enhance the study approach currently used by Idaho Power in performing North American Electric Reliability Corporation (NERC) compliance studies. Understanding the effects of extreme contingencies on vulnerabilities of Idaho Powers system is needed to determine when a disruption of service is likely to occur and how to take appropriate steps to reduce the associated risk. Identification of extreme contingencies using generation reallocation and load shedding for mitigation of their effects are illustrated using an IEEE RTS-96 test system and a model of the actual Idaho portion of the Western Electricity Coordinating Council (WECC) system.

Optimal PMU placement to achieve complete observability of Idaho Power Co. System

This paper presents an effective practical approach for identifying optimal locations of Phasor Measurement Units (PMUs) to achieve complete system observability. The approach, implemented in Physical and Operational Margins/Region Of Stability Existence (POM/ROSE) software, is based on automated iterative process of forming variables and constraints of a binary integer programming problem. The problem is then solved with standard linear programming solvers. The proposed approach was tested using Idaho Power Co. (IPC) system. It allows us to reduce the number of PMUs as compared to conventional techniques while maintaining complete system observability. A fast topological approach was also demonstrated and tested using IPC data in order to analyze the observability of the IPC network. The algorithm is fast and can be used in real-time as a part of bad data detection framework.

Node-breaker topology representation of Con Edison's Stations for planning studies

This paper describes a methodology and an automated process to implement node-breaker capabilities for representing major stations within Con Edisons footprint. This process creates a “hybrid” power flow model of Con Edisons system such that the user-defined stations are represented using the node-breaker model and the rest of the system is modeled using bus-branch representation. The process is implemented within the Physical and Operational Margins (POM) Suite software, which automatically expands the existing planning load flow case to incorporate nodebreaker modeling of the stations, and automatically generate breaker-oriented contingency lists. For those stations, which are represented using the node-breaker model, a breakeroriented contingency list is automatically generated. For the rest of the system, a contingency list consists of transmission line, transformer and generator outages. The breaker -oriented contingency list and the list of single element outages are automatically combined into one master contingency list. The “hybrid” model allows Con Edison to more accurately model contingencies for NERC-compliance studies.