Showing papers on "Blackout published in 2006"

The anatomy of a power grid blackout - Root causes and dynamics of recent major blackouts

Abstract: This paper examines some of the more recent major blackouts and discusses some of the root causes and dynamics of these events. The paper aims to identify high-level conclusions and recommendations for improving system dynamic performance and reducing the risk of such catastrophic events

Slow-Coherency-Based Controlled Islanding—A Demonstration of the Approach on the August 14, 2003 Blackout Scenario

Abstract: This paper demonstrates the use of a slow-coherency-based generator grouping algorithm and a graph theoretic approach to form controlled islands as a last resort to prevent cascading outages following large disturbances. The proposed technique is applied to a 30 000-bus, 5000-generator, 2004 summer peak load, Eastern Interconnection data and demonstrated on the August 14, 2003 blackout scenario. Adaptive rate of frequency decline-based load shedding schemes are used in the load rich islands to control frequency. The simulation results presented show the advantage of the proposed method in containing the impact of the disturbance within the islands formed and in preventing the impact of the disturbance from propagating to the rest of the system. This is demonstrated by the significant reduction in line flows in the rest of the system and by improved voltage and relative angle characteristics. Based on the suggestion in the joint U.S.-Canadian task force final report on the blackout, load shedding without any islanding is also performed, and results obtained are compared with the proposed controlled islanding method. The islanding method outperforms the load shedding-only method in reducing the transmission line flows, but both methods have similar effects on voltage and relative angle behavior

A conceptual framework for the controlled islanding of interconnected power systems

Abstract: Controlled islanding is a special protection strategy aimed at preventing a system-wide blackout as a result of the cascading of low probability events. This letter addresses the main issues and proposes a conceptual framework for a centralized and proactive controlled islanding strategy.

Aspects on Power System Islanding for Preventing Widespread Blackout

Abstract: When interconnected power system out of step occurs, it is imperative to detect it rapidly, and islanding should be taken to prevent widespread blackout. This paper presents a review of the main aspects on power system islanding. Out of step detection methods are classified to six categories. Islanding schemes are outlined according to graph partitioning, minimal cutset enumeration and generator grouping. In addition, four types of load shedding schemes after islanding operation are discussed. Synchronized phasor measurements and AI technologies facilitates the out of step detection, and makes the adaptive islanding and load shedding scheme

Blackout Model Based on OPF and its Self-organized Criticality

Abstract: Based on the essence of self-organized criticality and optimal power flow (OPF), this paper develops a model to capture the cascading failures and blackouts in power systems, which avoids some shortcomings of existent blackout models. The proposed model contains two dynamics, one is the fast dynamics which simulates the serial blackouts in power system, and the other is the slow dynamics which reflects the growth of the power system. Simulations in IEEE-30 bus system with the proposed model show that, the processing of the cascading and blackout can be captured by the fast dynamics, together with the self-organized criticality property of fast dynamic respect to the micro-scale. Besides, the macro-scale of self-organized criticality of power system can be revealed from the viewpoint of total load demand vs. the total network transfer capability. Furthermore, improving the transmission ability of network could effectively prevent blackout and reduce its risk.

Failure Analysis on China Power Grid Based on Power Law

Abstract: This paper is concerned with the mechanism of blackouts in China power system from the viewpoint of self-organized criticality. By using two estimation algorithms of scaled window variance (SWV) and rescaled range-statistics (R/S), this paper studies the blackout data in China power system during 1988-1997. The result of analysis shows that the blackout data of 1994-1997 coincides well with the autocorrelation. Furthermore, it is found that the function of blackout probability vs. blackout size exhibits power law distribution.

Postmortem analysis and data validation in the wake of the 2004 Athens blackout

Abstract: On July 12, 2004 at 12:39 local time, the south part of the Hellenic Interconnected Transmission System (including Athens) was split from the rest of the system and collapsed, driving consumers with a total load of 4500 MW into blackout. Technical information about the causes, the evolution, and the consequences of the blackout are presented in this paper. Some qualitative conclusions drawn immediately after the blackout are presented, as well as the results of further studies, including detailed simulations with corrected data, generator adjustments, and protection considerations

Black start with dfig based distributed generation after major emergencies

Abstract: Grid connected distributed generation (DG) increases reliability and additional benefits for consumers as well as utilities The stable and reliable operation of a power system is necessary after major emergencies (or blackouts) following a major system event Distributed generation may be capable of black start and contribute to fast restoration process at medium to low voltage level A large scale voltage and frequency excursions may occur during the process of black start with distributed generation due to low inertia and intermittency in power generation Energy storage integrated with DG can absorb initial impact of central generation and ensure smooth load pickup during the restoration of a system In this paper, the process of black start with a doubly fed induction generator (DFIG) based wind turbine is addressed and energy storage in DC link of DFIG is used for fast restoration after blackout A control system has been developed for the process of black-start with DFIG A sequence of actions for black start procedure is presented and tested

Overview of the events and causes of the 2003 Italian blackout

Abstract: During the night of September 28th, 2003 the European interconnected grid faced a series of outages, which started with line flashovers to trees and line trips on the Swiss electricity transmission grids, close to the Italian border, and ended with the separation of the entire Italian system from the UCTE (Union for the Co-ordination of the Transmission of Electricity) grid. The interconnecting lines were already heavily loaded and the operator action was not sufficient in controlling the situation. Due to the large power unbalance following the separation, the Italian electrical system and a small part of the Swiss system, suffered an under-frequency transient. Unfortunately, the automatic load shedding procedure and the regulating action of generators were not able to avoid the blackout. The incident affected the whole peninsula (about 45 million people); full restoration took almost 19 hours. This paper provides a short description of the system operation right before the incident, and reports the main events that led to the blackout. The focus is put on some issues that have been identified as the main causes that resulted in the separation of the Italian system and in the blackout. Some issues related to the operation of the Italian defense plan and to the restoration process are also discussed, along with some countermeasures already in place

Postmortem analysis of power grid blackouts - The role of measurement systems

Abstract: Promptly following any blackout, an investigation is conducted to determine the who, what, where, when, why, and how. At the heart of the postmortem investigation is the detailed sequence of events. The sequence of events is based on vast amounts of data collected from multiple points in the system from myriad data collection instruments, some devoted to the purpose of supporting system disturbance postmortem analysis, others providing useful additional context or filling in missing gaps. The more that the investigators know about their available sources of data, and the inherent limitations of each, the better (and quicker) will be the analysis. This is especially important when a large blackout has occurred, wherein there is pressure to find answers quickly, but because of the size and complexity of the event, a deliberate and methodical investigation is necessary. This paper discusses the role that system monitoring plays in supporting the investigation of large-scale system disruptions and blackouts

Creating cascading failure scenarios in interconnected power systems

Abstract: The reported catastrophic failures of power systems from different geographical parts of the world often point to cascading outage events of system elements that eventually had led to system blackout. Although the initiating events of these cascading failures may, at times, be avoidable by vegetation management or proper protection settings, the occurrence of such an event as well as the eventual impact cannot always be predicted. There is much debate in the industry whether the operator has enough time to apply countermeasures to avoid blackouts. Besides, the process of determining effective countermeasures cannot be deemed accurate unless a system has been extensively studied for the occurrence of widespread blackouts. In this paper, methods to create different cascading failure scenarios are developed under credible contingency conditions. The methods are tested on the 118 bus test system and several cases are reported.

An approach to statistical estimation of cascading failure propagation in blackouts

Abstract: Load power is progressively shed as large, cascading blackouts of electric power transmission systems evolve. We pro- pose a statistical estimator to measure the extent to which the load shedding is propagated. The estimator uses data from a series of simulated blackouts. The estimator is derived from a continuous state branching process that is a high level probabilistic model of the cascading process. The estimator is tested on failure data generated by a power system model of cascading line outages. The estimates for propagation of load shed are consistent with estimates for the propagation of line outages. Estimating the initial load shed and the propagation of load shed leads to estimates of the probability distribution of blackout size. This work opens up possibilities of monitoring infrastructure failures to quantify the vulnerability to cascading and the overall risk of large cascading failures.

Review of Blackout in Hainan on September 26th——Causes and Recommendations

Abstract: On September 26, 2005, large portions of Hainan province, China, experienced an electric power blackout as a result of Damrey typhoon. This is the first blackout of provincial power grid in China, and it's also the first successful case of black-start in Chinese power grid. There are many experiences and lessons can be drawn from the Sept. 26, 2005 blackout. This paper tries to demonstrate the scenarios of this blackout and subsequent black-start in details. Then, the focus is put on the inherent causes leading to the problems exposed in this blackout. Some recommendations preventing or minimizing the scope of future blackouts are proposed.

The 1987 Tokyo Blackout

Abstract: On July 23, 1987, the metropolitan Tokyo area experienced a massive blackout caused by voltage instability. In the blackout, more than 8 GW of load was lost for about 3.35 hours at most, which affected 2.8 million households. Lessons learned from the blackout have formed the foundation of voltage and reactive power control, currently adopted in the Tokyo Electric Power Company (TEPCO) network

Analysis of ferroresonant overvoltages at Maanshan Nuclear Power Station in Taiwan

Abstract: The "318 Blackout Incident" at the Maanshan Nuclear Power Station on March 18, 2001, is considered to be the most serious event over the 24-year history of nuclear power generation in Taiwan. This paper simulates a special overvoltage phenomenon that occurred 4 h before the blackout event, which could have caused the incident. The simulation results almost coincide closely with the actual conditions recorded. We found two major low-frequency and ferroresonant overvoltages caused by the motors which acted as generators when they lost power supply, interacting with power-line capacitance and power transformers. Since overvoltages were present for a short period, the breaker insulation did not break down immediately but the defects were accumulated. A blackout eventually occurred 4 h later, when the power supplied to the 4.16-kV essential bus A changed over from the 161-kV system to the 345-kV system, due to damage in the incoming breaker insulation.

Research on Sensitivity Analysis for Composite Generation and Transmission System Reliability Evaluation

Abstract: The sensitivity information for reliability of composite generation and transmission system is useful for planning studies, as it can effectually identify the critical components and system ldquobottlenecksrdquo, thereby an important guiding can be offered for power system planning. The importance and necessity of conducting sensitivity studies on bulk power system reliability assessment have been increasingly recognized in recent years because of some fatal blackouts throughout the world, especially the August 14th blackout in the United States and Canada. This paper proposes a set of formulae which are defined as the partial derivation of the reliability indices such as loss of load probability (LOLP), loss of load frequency (LOLF) and expected demand not supplied (EDNS) with respect to components parameters such as availability, unavailability, failure rate and repair rate. By use of Lagrange multiplies for equality and inequality constraints in linear programming based optimal load shedding model, the partial derivation of EDNS with respect to component capacity is presented. The sensitivity analysis method is verified by the reliability evaluation for IEEE-RTS79 test system.

Phasor measurement systems in the WECC

Abstract: This paper presents the use of phasor measurement units (PMUs) in the Western Electric Coordinating Council (WECC) has been very successful. Phasor data recorded during the Aug. 10, 1996 blackout showed the phase difference growing as the system weakened well before system separation. It also showed clearly the dynamic system behavior before and during the blackout. WAMS measurements, particularly phasor measurements, filled the need to see system behavior that other measurements did not cover. Phasor measurements are now widely dispersed in the WECC, most of the in real-time systems. More of these are being connected in wide-area networks to support continuing efforts to improve operations.

New wide-area algorithms for detecting angle instability using synchrophasors

Abstract: Electric power system is undergoing major technological advances with many new installations of synchrophasors across the North American grid as well in power systems all over the world. Wide-area monitoring system (WAMS) in the Pacific Northwest and the Eastern Interconnection Phasor Project (EIPP) in the eastern grid are examples of such installations. Synchrophasors together with modern communication technology facilitate the monitoring of the current state of the power system including the phase angles of the bus voltages at critical buses in a time-synchronized fashion. Power system operation is constantly facing contingencies such as from line faults and generator outages. For operational reliability, the system must be able to withstand all credible contingencies, either by itself (for N-1 contingency) or with the help of Special Protection Schemes (SPS) or Remedial Action Schemes (RAS) (for N-2 or worse contingencies). However, when the system is operating under unforeseen conditions or under unusually high stress, the system can experience the angle instability. In that case, the system breaks up into many islands, resulting in large loss of loads and generations and a potential blackout scenario. In this paper, new algorithms are proposed for detecting the emergence of angle instability phenomenon while it is still evolving so that suitable countermeasures can be initiated to prevent the islanding. The proposed algorithms and the controller detect the fast separation of phase angles among the critical areas automatically by using the synchrophasors, and proceed to mitigate the instability by suitable switching action. Briefly, the algorithms initiate tripping of critical generators in the accelerating part of the system when necessary, and also initiate load shedding in the decelerating part of the system whenever necessary. The novelty of the algorithms is in the fact that all the decisions are made in real-time purely based on the wide-area synchrophasor measurements without any knowledge of the details of the relay actions that may have resulted in the angle stability phenomenon. The concept of a real-time transient energy function method for the large power system is also explored to solve the problem. The paper will discuss the new algorithms along with illustrative examples on standard IEEE test systems.

Incorporation of N-1 Security into Optimal Power Flow for FACTS Control

Abstract: As the electric power consumption increases continuously, the stress on the power grid grows and therefore, failures of system components become more probable. When the system is not in an N-1 secure state, an outage of a single component may trigger cascading failures in the worst case resulting in a blackout. In this paper, a new current injection method is developed such that the apparent power flows on lines in case of a line failure are very accurately determined by a linear equation system. Based on this, a method using FACTS devices to keep the system in an N-1 secure state is presented. The set values of the FACTS devices are determined by an optimal power flow (OPF) control where the current injection method is used to include N-1 considerations focused on line failures. Thus, a control strategy is outlined which reduces the risk of cascading failures

Timing of a Controlled Islanding Strategy

Abstract: Controlled islanding is a 'last line of defense' for avoiding catastrophic blackouts in an electric power system approaching global instability. The design of an intentional controlled islanding strategy must be inherently predictive in nature, as well as reliable. An algorithm is presented that monitors the synchronous stability of the system at a global level using the Prony method, and is coupled with detection of local out-of-step conditions to decide when controlled islanding should be initiated. The boundaries of the islands are derived from the groups of slow coherent generators. The objective is to minimize the potential blackout extent in the system

Basic Research Needs for Superconductivity. Report of the Basic Energy Sciences Workshop on Superconductivity, May 8-11, 2006

Abstract: As an energy carrier, electricity has no rival with regard to its environmental cleanliness, flexibility in interfacing with multiple production sources and end uses, and efficiency of delivery. In fact, the electric power grid was named ?the greatest engineering achievement of the 20th century? by the National Academy of Engineering. This grid, a technological marvel ingeniously knitted together from local networks growing out from cities and rural centers, may be the biggest and most complex artificial system ever built. However, the growing demand for electricity will soon challenge the grid beyond its capability, compromising its reliability through voltage fluctuations that crash digital electronics, brownouts that disable industrial processes and harm electrical equipment, and power failures like the North American blackout in 2003 and subsequent blackouts in London, Scandinavia, and Italy in the same year. The North American blackout affected 50 million people and caused approximately $6 billion in economic damage over the four days of its duration. Superconductivity offers powerful new opportunities for restoring the reliability of the power grid and increasing its capacity and efficiency. Superconductors are capable of carrying current without loss, making the parts of the grid they replace dramatically more efficient. Superconducting wires carry up tomore » five times the current carried by copper wires that have the same cross section, thereby providing ample capacity for future expansion while requiring no increase in the number of overhead access lines or underground conduits. Their use is especially attractive in urban areas, where replacing copper with superconductors in power-saturated underground conduits avoids expensive new underground construction. Superconducting transformers cut the volume, weight, and losses of conventional transformers by a factor of two and do not require the contaminating and flammable transformer oils that violate urban safety codes. Unlike traditional grid technology, superconducting fault current limiters are smart. They increase their resistance abruptly in response to overcurrents from faults in the system, thus limiting the overcurrents and protecting the grid from damage. They react fast in both triggering and automatically resetting after the overload is cleared, providing a new, self-healing feature that enhances grid reliability. Superconducting reactive power regulators further enhance reliability by instantaneously adjusting reactive power for maximum efficiency and stability in a compact and economic package that is easily sited in urban grids. Not only do superconducting motors and generators cut losses, weight, and volume by a factor of two, but they are also much more tolerant of voltage sag, frequency instabilities, and reactive power fluctuations than their conventional counterparts. The challenge facing the electricity grid to provide abundant, reliable power will soon grow to crisis proportions. Continuing urbanization remains the dominant historic demographic trend in the United States and in the world. By 2030, nearly 90% of the U.S. population will reside in cities and suburbs, where increasingly strict permitting requirements preclude bringing in additional overhead access lines, underground cables are saturated, and growth in power demand is highest. The power grid has never faced a challenge so great or so critical to our future productivity, economic growth, and quality of life. Incremental advances in existing grid technology are not capable of solving the urban power bottleneck. Revolutionary new solutions are needed ? the kind that come only from superconductivity.« less

Study on Security Protection of Transmission Section and Its Key Technologies

Abstract: Cascading overload trip due to lack of transmission section protection is an important reason of large scale blackout. This paper first illustrates the meaning of transmission section and points out that the objective of transmission security protection is to maintain its integrality and transmission capacity, and to avoid cascading overload trip. In addition, the implement condition and key technology are discussed, which are online capture of transmission section, real-time prediction of cascading overload and real-time emergency control to avoid cascading trip. This paper has brought forward the primary scheme. Its validity is verified by the calculation result of CEPRI 36 test system.

Modeling and analysis of power system events

Abstract: The events in power systems are an important dynamic behavior, and there is no good approach of modeling and analysis at all times due to the complexity of its behaviors. In this paper, a mathematic definition of the event is given after analyzing various power system events, and also gives a model framework of power system events, which is based on formal language theory. The hybrid dynamic behavior between power system discrete control actions and physical system is analyzed by using this framework, and a cascading event sequence occurred in the 8.14 blackout is used as an example to discuss the controllable of events. Then, the synthesis of supervisor of power system discrete events is also discussed.

Shining Examples of Service When the Lights Went Out: Hotel Employees and Service Recovery during the Blackout of 2003

Abstract: The electrical outage in the summer of 2003 that interrupted power to thousands of hotels wrought a variety of facilities failures and service-process problems. Fortunately, strong service-recovery efforts from hotel employees mitigated the worst of the blackout's effects. Using survey data from hotel managers who experienced the blackout, this study highlights those employee actions that most contributed to immediate service recovery; however, the study also reveals limited organizational learning or efforts to failsafe hospitality service from the eventuality of future power failures.

Data Envelopment Analysis Based Relative Effectiveness Assessment of Power System Black-start Plans

Abstract: Restoration of a power system after a complete blackout is a very important issue to the safety of the power system. Reasonable black-start plans are necessary to restore the power system as soon as possible. Based on data envelopment analysis, a new method for assessing black-start plans is proposed in this paper. Technical verification of the plans is considered in the assessment process. Whether a plan is effective is defined by its input and output index values entirely. The application to a practical power system verifies that the method could provide dispatchers more comprehensive and objective decision references.

WAMS Based Flow Transfer Identification Algorithm

Abstract: In view of the cascading trip induced by backup relays that affects the safe operation of the system and may even cause blackout, after investigating the defects of the existing backup protection, this paper presents a new wide area backup protection strategy based on WAMS to identify the flow transfer. A new concept of flow transfer relativity factor (FTRF) is proposed to estimate the flow distribution after flow transfer occurs, and the strict definition and calculating method are presented. The simulation in a three-machine network shows that the wide-area backup protection strategy proposed to identify flow transfer works well.

Preliminary Analysis of Large Scale Blackout in Western Europe Power Grid on November 4 and Measures to Prevent Large Scale Blackout in China

Abstract: The “11.4” blackout in Western Europe is a large outage in European history. The development and recovery process of this outage is introduced here. According to the investigation reports of the “9.23” Sweden–Denmark blackout and “9.28” Italy blackout and “11.4” Western Europe blackout, the results of these investigations are analyzed. Based on these blackouts some problems in European power grid are indicated. Suggestions for developing new technologies to prevent large scale blackout in China are presented.

Criticality in a cascading failure blackout model

Abstract: We verify and examine criticality in a 1000 bus network with an AC blackout model that represents many of the interactions that occur in cascading failure. At the critical loading there is a sharp rise in the mean blackout size and a power law probability distribution of blackout size that indicates a significant risk of large blackouts.

A Preliminary Research on Power System Cascading Contingency Forecasting

Abstract: In recent years, cascading contingency become important cause leading to large-scale blackout of power grids, so it is of significance for prevention of large-scale blackout to effectively forecast the following-up failure that could occur. On the basis of analyzing the evolution law of a cascading accident during the initial stage in detail, a method by which the following-up failure can be forecasted is proposed. This method can effectively take the interaction between previous failure and following-up failure into account as well as the cumulative influence of all happened faults, and rapidly forecast following-up failure that could occur. This research is an attempt to seek an effective method for prevention of large-scale blackout.