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From the perspective of self-organized criticality, this paper develops a novel model with ac-OPF and ac grid upgrade to study the cascading failures and blackouts in power systems, which overcomes some shortcomings of existing blackout models. The proposed model contains two types of dynamics, one is fast dynamics which simulates the serial blackouts in power systems, the other is slow dynamics which reflects the tendency of the power systems time evolution. This model also has voltage stability analysis function and can reveal critical characteristics from reactive power and voltage viewpoint. Simulation results of the IEEE 118-bus system with this model show that the fast dynamics can capture the cascading process and the criticality property in micro scale. Besides, the macro scale of self-organized criticality of power systems can be revealed from the mean value of fractional overloads and the ratio of total load demand to the total network transfer capability. Furthermore, the voltage stability criticality status could be detected from the eigenvalue with the smallest magnitude through reactive power and voltage relevant modal analysis. Index Terms--Blackout model, cascade failures, optimal power flow, self-organized criticality, voltage stability.

Although phasor measurement units (PMUs) have become increasingly widespread throughout power networks, the buses monitored by PMUs still constitute a very small percentage of the total number of system buses. Our research explores methods to derive useful information from PMU data in spite of this limited coverage. In particular, we have developed an algorithm which uses known system topology information, together with PMU phasor angle measurements, to detect system line outages. In addition to determining the outaged line, the algorithm also provides an estimate of the pre-outage flow on the outaged line. To demonstrate the effectiveness of our approach, the algorithm is demonstrated using simulated and real PMU data from two systems--a 37-bus study case and the TVA control area. Index Terms--Event detection, line outages, phasor measurement units.

We study cascading transmission line outages recorded over nine years in an electric power system with approximately 200 lines. The average amount of propagation of the line outages is estimated from the data. The distribution of the total number of line outages is predicted from the propagation and the initial outages using a Galton-Watson branching process model of cascading failure. Index Terms--Failure analysis, power systems, reliability, risk analysis.

Under normal operating conditions, a MicroGrid is interconnected with the medium voltage network; however, in order to deal with black start and islanded operation following a general blackout, an emergency operation mode must be envisaged. A sequence of actions and conditions to be checked during the restoration stage are identified and tested through numerical simulation. Voltage and frequency control approaches, inverter control modes, and the need of storage devices are addressed in this paper in order to ensure system stability, achieve robustness of operation, and not jeopardize power quality during service restoration in the low voltage area. Index Terms--Dynamic response, energy storage, frequency control, microgrid, power system dynamic stability, power system restoration.

We show how concepts from game theory can be used to find and evaluate strategies for defending an electric power system against antagonistic attacks. Consequently, the interaction between the antagonist and the defender of the system is envisaged as a game. In a numerical example, we study the performance of different defense strategies against a number of attack scenarios. Particularly, we study whether there is a dominant defense strategy and an optimal allocation of resources between protection of components and recovery. Index Terms--Blackout, game theory, homeland security.

This paper presents a new method for an optimal measurement placement of phasor measurement units (PMUs) for power system state estimation. The proposed method considers two types of contingency conditions (i.e., single measurement loss and single-branch outage) in order to obtain a reliable measurement system. First, the minimum condition number of the normalized measurement matrix is used as the criteria in conjunction with the sequential elimination approach to obtain a completely determined condition. Next, a sequential addition approach is used to search for necessary candidates for single measurement loss and single-branch outage conditions. These redundant measurements are optimized by binary integer programming. Finally, in order to minimize the number of PMU placement sites, a heuristic technique to rearrange measurement positions is also proposed. Numerical results on the IEEE test systems are demonstrated. Index Terms--Contingency, measurement placement, phasor measurement units (PMUs), state estimation.

This paper develops statistical models for estimating the impacts of tree trimming on electric power system outages under normal (nonstorm) operating conditions. The models are based on an extensive data set from Duke Power, a company in the southeastern U.S., and the models used are a negative binomial generalized linear model and a Poisson generalized linear mixed model (GLMM). The results show that: 1) increasing tree trimming frequency does lead to a decrease in the number of outages on the electric power distribution system; 2) the effects of tree trimming on different circuits can be differentiated and measured; and 3) the Poisson GLMM provides a good fit to the data in this situation. In particular, the results of the model show that for the Duke Power system, one would have expected, on average, 0.9 fewer outages per circuit over the 43-month data recording period if the time between tree trimming cycles was decreased by 1 yr across the whole system. These models could be applied to other power systems, and the results should be useful for power managers in setting tree trimming frequencies and in focusing on the most frequent trimming efforts on those circuits for which trimming will have the greatest benefit. Index Terms--Power distribution maintenance, power distribution reliability, statistics, vegetation.

On August 14, 2003, a cascading outage of transmission and generation facilities in the North American Eastern Interconnection resulted in a blackout of most of New York state as well as parts of Pennsylvania, Ohio, Michigan, and Ontario, Canada. On September 23, 2003, nearly four million customers lost power in eastern Denmark and southern Sweden following a cascading outage that struck Scandinavia. Days later, a cascading outage between Italy and the rest of central Europe left most of Italy in darkness on September 28. These major blackouts are among the worst power system failures in the last few decades. The Power System Stability and Power System Stability Controls Subcommittees of the IEEE PES Power System Dynamic Performance Committee sponsored an all day panel session with experts from around the world. The experts described their recent work on the investigation of grid blackouts. The session offered a unique forum for discussion of possible root causes and necessary steps to reduce the risk of blackouts. This white paper presents the major conclusions drawn from the presentations and ensuing discussions during the all day session, focusing on the root causes of grid blackouts. This paper presents general conclusions drawn by this Committee together with recommendations based on lessons learned. Index Terms--Blackouts, power system control, power system dynamic performance, power system stability.

The paper provides a review of the electrocution and collision hazards of overhead distribution lines of large birds, particularly raptors, which can be reduced through modifications to existing design standards. The modifications to overhead distribution lines discussed in the paper include pole-line reconfiguration, the use of cover-up materials, perch deterrents, and line markers. The paper also discusses the effectiveness of these measures and research that is under way to develop tools to better understand where the problems are occurring and to determine if existing mitigating measures are working. Index Terms--Animals (birds, raptors), collisions, electrocution.

We analyze a 15-year time series of North American electric power transmission system blackouts for evidence of self. organized criticality (SOC). The probability distribution functions of various measures of blackout size have a power tail and rescaled range analysis of the time series shows moderate long-time correlations. Moreover, the same analysis applied to a time series from a sandpile model known to be self-organized critical gives results of the same form. Thus, the blackout data seem consistent with SOC. A qualitative explanation of the complex dynamics observed in electric power system blackouts is suggested. Index Terms--Blackouts, complex systems, power system security, reliability, risk analysis, time series.

About every four months, the United States experiences a blackout large enough to darken half a million homes. As long ago as 1965, a massive blackout in New York captured […]

The manufacturing segment in Nigeria sufferes considerable loss of electricity, indicating a need for increased supply.

Research on semiactive control of structures has been carried out actively since the middle of the 1990s. After a theoretical and experimental study, a semiactive structural control system has been applied to an actual five-story building in 1998 by use of a continuous-variable semiactive hydraulic damper that has a maximum damping force of 1,000 kN. For application of the system, health monitoring, fail-safe operation, possibility of power failure, sensor malfunction, control device operation, computer, and communication system, etc., need to be considered. In this paper, reliability of an operational semiactive structural control system is discussed from the view points of health monitoring of the system and fail-safe functions. Power failures, abnormal outputs of sensors, valve damages, and communication errors, are focused as main problems. Dynamic load and forced vibration tests were carried out to determine fail-safe functions. After completion of the system installation, monitoring for earthquake excitation was initiated. Results presented show the effectiveness of functioning of the system. Finally, reliability of the system is confirmed and satisfactory performance is demonstrated. DOI: 10.1061/(ASCE)0733-9445(2003)129:7(914) CE Database subject headings: Active control; Damping; Reliability; Power loss.

A set of equations is developed in this paper and used in conjunction with the minimal cut set method [1] to evaluate the total failure frequency of a parallel redundant system consisting of series components in each branch where each component can operate in its wearout period and the failure rate of each component is not constant. The optimum maintenance intervals are determined based on the criterion that the total failure frequency of the system is minimized. The Newton-Raphson method is applied to obtain the unknown optimum maintenance intervals for the system. The proposed approach is presented and illustrated using a practical substation example.

It is shown that currently used apparent power definitions, namely the Arithmetic VA, SA and the Vector VA, [S.sub.A], both lack an important property: The system power losses are not a linear function of the apparent power squared, [Mathematical Expression Omitted] or [Mathematical Expression Omitted]. The only apparent power definition known today, that holds this property for all the possible situations - balanced, unbalanced, sinusoidal or nonsinusoidal - has the mathematical expression suggested by F. Buchholz and explained by W. Goodhue. This paper gives a set of basic examples meant to emphasize the merit of Buchholz-Goodhue approach. Key Words: Power Definitions. Load Unbalance. Nonsinusoidal Conditions.

Utilities strive to have quick restoration after a power outage. Extreme conditions, such as storms, create difficult restoration challenges because of the large number of tasks necessary to restore power to many affected customers. Restoration efforts can be further hindered when outage report escalation algorithms predict the wrong location for affected devices. This paper describes a modified topological based algorithm that associates trouble calls with each other to provide more accurate information about outages during heat storms. The heat storm algorithm was tested and verified on two feeders using test cases that simulated the heat storm conditions experienced at Northern States Power Company in Minneapolis, Minnesota in July 1995. Keywords: Power System Restoration, Power Distribution Faults, Storm Management

A feasibility study on the characterization of incipient insulator failure for distribution fault prediction is presented. In this study, real distribution data was collected and analyzed to isolate incipient failure signatures or parameters which were expected to show distinct behaviors before and after failure incident. Several signal analysis methods were applied to isolate the parameters and a new strategy of analysis, the event-date concept, was also applied to find a relationship between non-harmonic and high frequency signal activities and imminent insulator failures. Keywords: Failure prediction, incipient fault, insulator, data analysis, predictive maintenance

As the power industry moves into a new competitive era, the reliability of radial distribution feeders becomes a primary issue in comparing the 'new' versus the 'old' way of serving customers. In order to make the comparison, a distribution engineer needs to have the analysis tools to perform the necessary reliability studies. For the purposes of this paper, the reliability studies will be limited to the calculation of the annual 'outage rate' and associated 'restoration time' for a typical customer on a radial distribution feeder. This paper will develop the background and theory for computing these reliability indices. The method can be applied to demonstrate how different devices and/or feeder configurations affect the average customer on a specific feeder. Index Terms - Distribution, feeder, outage rate, radial, reliability.

A generation system is considered to be capable of serving a target firm load that is consistent with accepted operating criteria. This target is referred to as the firm load carrying capability of a system. The same generation system may be capable of supporting a limited amount of interruptible load on top of the firm load without violating the operating criteria. This capability is defined as the interruptible load carrying capability (ILCC) of the system. This paper presents a probabilistic technique to evaluate the ILCC of isolated and interconnected systems. The objective is to determine the amount of interruptible load and the corresponding interruption time that can maximize the expected energy supplied while satisfying the operating criteria. The operating criteria are defined using a well-being framework. Study results are illustrated using the IEEE-RTS.

This paper investigates impacts of energization transients of large shunt reactors on the operation of HVAC and HVDC/AC power systems. The Electromagnetic Transients Program for DC systems (EMTDC) is used for the simulation studies. The studies conclude that shunt reactor energization can result in undesirable response of power system apparatus and even interruption of power flow, e.g. commutation failure of HVDC converters. The studies also indicate that the energization transients can be adequately alleviated based on the use of pre-insertion resistor and/or controlled energization strategies. Keywords - Reactor Energization; Pre-insertion Resistor; Synchronous Switching; HVDC Transients; HVAC Transients.

Reliability worth assessment using customer interruption costs is an important element in electric power system planning and operation. This paper deals with two features that affect the composite generation-transmission system reliability worth assessment. One feature is the incorporation of temporal variations in the cost of interruption. This paper illustrates the effect on the expected annual system outage cost of temporal variation in the interruption costs for the residential, agricultural, industrial, commercial and large user sectors. The other aspect considered in this paper is using a probability distribution approach to represent the cost of interruption model. The conventional customer damage function approach utilizes average customer costs while the probability distribution approach recognizes the dispersed nature of the customer outage data. These two methods of cost evaluation are applied to reliability worth assessment in this paper. A sequential Monte Carlo approach incorporating time varying loads is used to conduct all the studies. Case studies performed on two composite test systems show that incorporating time varying costs of interruption for the industrial sector resulted in a significant reduction in the expected outage cost. A comparison of the reliability worth obtained using the customer damage function method (CDF) with the probability distribution approach suggests that using the CDF method may significantly undervalue the reliability worth by a factor of three to four.