Modern power systems are now stepping into the post-restructuring era, in which utility industries as well as ISOs (Independent System Operators) are involved. Attention needs to be paid to the reliability study of power systems by both the utility companies and the ISOs. An uninterrupted and high quality power is required for the sustainable development of a technological society. Power system blackouts generally result from cascading outages. Protection system hidden failures remain dormant when everything is normal and are exposed as a result of other system disturbances. This dissertation provides new methods for power system vulnerability analysis including protection failures. Both adequacy and security aspects are included. The power system vulnerability analysis covers the following issues: 1) Protection system failure analysis and modeling based on protection failure features; 2) New methodology for reliability evaluation to incorporate protection system failure modes; and, 3) Application of variance reduction techniques and evaluation. A new model of current-carrying component paired with its associated protection system has been proposed. The model differentiates two protection failure modes, and it is the foundation of the proposed research. Detailed stochastic features of system contingencies and corresponding responses are considered. Both adequacy and security reliability indices are computed. Moreover, a new reliability index ISV (Integrated System Vulnerability) is introduced to represent the integrated reliability performance with consideration of protection system failures. According to these indices, we can locate the weakest point or link in a power system. The whole analysis procedure is based on a non-sequential Monte Carlo simulation method. In reliability analysis, especially with Monte Carlo simulation, computation time is a function not only of a large number of simulations, but also time-consuming system state evaluation, such as OPF (Optimal Power Flow) and stability assessment. Theoretical and practical analysis is conducted for the application of variance reduction techniques. The dissertation also proposes a comprehensive approach for a TTC (Total Transfer Capability) calculation with consideration of thermal, voltage and transient stability limits. Both steady state and dynamic security assessments are included in the process of obtaining total transfer capability. Particularly, the effect of FACTS (Flexible AC Transmission Systems) devices on TTC is examined. FACTS devices have been shown to have both positive and negative effects on system stability depending on their location. Furthermore, this dissertation proposes a probabilistic method which gives a new framework for analyzing total transfer capability with actual operational conditions.

Modern power systems are now stepping into the post-restructuring era, in which utility industries as well as ISOs (Independent System Operators) are involved. Attention needs to be paid to the reliability study of power systems by both the utility companies and the ISOs. An uninterrupted and high quality power is required for the sustainable development of a technological society. Power system blackouts generally result from cascading outages. Protection system hidden failures remain dormant when everything is normal and are exposed as a result of other system disturbances. This dissertation provides new methods for power system vulnerability analysis including protection failures. Both adequacy and security aspects are included. The power system vulnerability analysis covers the following issues: 1) Protection system failure analysis and modeling based on protection failure features; 2) New methodology for reliability evaluation to incorporate protection system failure modes; and, 3) Application of variance reduction techniques and evaluation. A new model of current-carrying component paired with its associated protection system has been proposed. The model differentiates two protection failure modes, and it is the foundation of the proposed research. Detailed stochastic features of system contingencies and corresponding responses are considered. Both adequacy and security reliability indices are computed. Moreover, a new reliability index ISV (Integrated System Vulnerability) is introduced to represent the integrated reliability performance with consideration of protection system failures. According to these indices, we can locate the weakest point or link in a power system. The whole analysis procedure is based on a non-sequential Monte Carlo simulation method. In reliability analysis, especially with Monte Carlo simulation, computation time is a function not only of a large number of simulations, but also time-consuming system state evaluation, such as OPF (Optimal Power Flow) and stability assessment. Theoretical and practical analysis is conducted for the application of variance reduction techniques. The dissertation also proposes a comprehensive approach for a TTC (Total Transfer Capability) calculation with consideration of thermal, voltage and transient stability limits. Both steady state and dynamic security assessments are included in the process of obtaining total transfer capability. Particularly, the effect of FACTS (Flexible AC Transmission Systems) devices on TTC is examined. FACTS devices have been shown to have both positive and negative effects on system stability depending on their location. Furthermore, this dissertation proposes a probabilistic method which gives a new framework for analyzing total transfer capability with actual operational conditions.

While two objectives of deregulation are to reduce service interruptions and achieve lower energy costs, deregulation has actually introduced new problems in both areas. Since the transmission network was built in the last century, mainly for the regulated power systems, with mostly local power transfers, the increased long distance power transfer introduced by free energy trading has made congestion happen more frequently. When congestion happens, service interruptions occur and higher energy costs arise. We approach the issue from the viewpoints of both planning and online operations. Accordingly, we develop a reactive online remedying method that uses Flexible AC Transmission (FACTS) devices to eliminate congestion with minimum transaction curtailment to maintain market force. We also develop a proactive preventive method for offline planning, such as in the day-ahead market, which uses FACTS devices to maximize the Total Transfer Capability so that more transactions can be scheduled without causing congestion in the system. Optimal Power Flow is used for both methods with FACTS devices treated as control variables so that they can be adjusted to the best FACTS parameters to minimize the transaction curtailment or maximize the Total Transfer Capability. We demonstrate that FACTS devices are very effective for both situations. Since the installation of FACTS devices involves heavy infrastructure investment, an effective pricing method needs to be in place to encourage this investment by guaranteeing sufficient return. This research uses a novel pricing scheme to charge for both utilizing the FACTS devices and having the FACTS devices operating at their limits. The owners of the FACTS devices will then be able to recover their investment. With the above control method and the pricing method, we can make better use of the existing transmission network and relieve congestion. However, deregulation may also degrade system reliability since the generation companies are not obligated to sell into the market and market participation is driven by market forces instead. We use the market share based short-term adequacy analysis method to address generation resource adequacy issues. The market share based method uses the market share time series for the generation companies to reflect their market behavior in the new environment. Multiple regression modeling, a tool of time series analysis, is used to model involved factors. We demonstrate how the market share based short-term adequacy analysis method can capture the adequacy problems that the traditional method cannot. In addition, it can also help to remedy the adequacy problems, which can in turn reduce service interruption and thus the energy price.

Since the deregulation of power systems was started in 1989 in the UK, many countries have been motivated to undergo deregulation. The United State started deregulation in the energy sector in California back in 1996. Since that time many other states have also started the deregulation procedures in different utilities. Most of the deregulation market in the United States now is in the wholesale market area, however, the retail market is still undergoing changes. Deregulation has many impacts on power system network operation and control. The number of power transactions among the utilities has increased and many Independent Power Producers (IPPs) now have a rich market for competition especially in the green power market. The Federal Energy Regulatory Commission (FERC) called upon utilities to develop the Regional Transmission Organization (RTO). The RTO is a step toward the national transmission grid. RTO is an independent entity that will operate the transmission system in a large region. The main goal of forming RTOs is to increase the operation efficiency of the power network under the impact of the deregulated market. The objective of this work is to study Internet based Wide Area Information Sharing (WAIS) applications in the deregulated power system. The study is the first step toward building a national transmission grid picture using information sharing among utilities. Two main topics are covered as applications for the WAIS in the deregulated power system, state estimation and Total Transfer Capability (TTC) calculations. As a first step for building this national transmission grid picture, WAIS and the level of information sharing of the state estimation calculations have been discussed. WAIS impacts to the TTC calculations are also covered. A new technique to update the TTC using on line measurements based on WAIS created by sharing state estimation is presented. / Ph. D.

The transition of the power sector from vertically integrated utility (VIU) to deregulated system has resulted in reshaping of generation, transmission and distribution components. Some of the objectives of restructuring are to ensure a secure and reliable supply of electricity, encourage competition in all segments, sustain future economic and technological growth, etc. There are many challenges that arise in fulfilling these objectives. The thesis addresses some of them related to planning and operational aspects of real and reactive power, covering the following areas: Real power tracing, loss allocation and pricing Reactive power tracing, loss allocation and pricing Power system generation expansion planning Power transfer capability in interregional grids Voltage stability enhancement by improving reactive power margins In deregulated power systems, it has become important to identify the generation and transmission entities responsible in meeting loads. This is done by tracing the power flows through the transmission network. Power tracing is required to assess the extent of network usage by the participants, so as to allocate the transmission losses and charges. Many loss allocation methods are presented in the literature. The loss allocation method implemented in this thesis is a circuit based method. For obtaining the generators contribution towards meeting system loads and transmission losses, an approach of relative electrical distance (RED) between the generation and the load buses, is presented. The method is used to trace both real and reactive power flows. In the case of real power, the generators are the only sources and loads are the only sinks. However, reactive sources and sinks are distributed all along the transmission system. The reactive power sources considered are generators, switchable VAR sources (shunt capacitor banks) and line charging susceptances; and the reactive sinks are shunt reactors and reactive inductive loads. While tracing their flows the actual sources or sinks are to be identified which is obtained after adding reactive injections and absorptions at each bus. If the net value is absorbing, the bus is a reactive sink and if the net value is injecting, the bus is a reactive source. The transmission line charge susceptances contribution to the system’s reactive flows; and its aid extended in reducing the reactive generation at the generator buses is also discussed. A reactive power optimization technique is applied to optimally adjust the reactive controller settings of transformer taps, generator excitations and switched capacitors, so that the available reactive resources can be fully utilized. In the thesis, a methodology for evaluation of real and reactive power load and loss sharing proportions; and cost allocation towards transmission utilization is presented. Due to the ever growing increase in demands; on one hand the existing transmission networks are getting overloaded at some locations and on the other hand, the available generation is becoming insufficient to cater to the additional demand. To handle this problem, generation and transmission expansions become inevitable. Hence, additional public sector units or independent power producers and transmission providers are to be brought in. However in a restructured system, generally there is no central planning for new generation capacity or transmission additions. The reason being, these investments need huge capital and long period of commitment. While making a generation investment decision, expectations concerning future electricity demand, spot market prices, variations of regulatory policies, etc., are the major considerations. The locations, capacities and timing of new power plants are basically at the generation companies’ own discretion. Also, generation companies do not have any obligation to ensure sufficient supply of electricity to meet present and future requirements. Hence, it is a matter of concern as to how adequate generation capacity can be secured in the long run. Optimal siting and sizing of these new generation locations is also an issue of concern. In this thesis a new index called as ‘Tindex’ is proposed, which identifies prospective new generation expansion locations. The index is formulated based on the transmission network information, and it helps in identifying the most suitable new generation expansion locations. To implement this methodology each of the load bus is treated as a generation bus, one at a time, and the maximum generation capacity that can be installed at the location is computed from the approach. This method ensures minimum transmission expansion. Interconnected power systems help in exchanging power from one area to other areas at times of power deficiency in their own area. To enable this, their tieline capability to transfer power has to be sufficient, which is determined using total transfer capability (TTC) computation. TTC is an important index in power markets with large volume of interarea power exchanges and wheeling transactions taking place on an hourly basis. In the thesis, the total transfer capability (TTC) of interconnected tielines, under normal and contingency conditions is evaluated. The contingency cases evaluated are single line contingency, tieline contingency and generator outage. The most critical lines in each zone are identified using Fuzzy set theory. Unified power flow controller (UPFC), a flexible AC transmission system (FACTS) device is incorporated to improve the power transfers under contingency conditions. The best locations for UPFC placement are identified by analysing the power flow results obtained after considering the contingencies. For each of the normal and contingency cases, a base case and a limiting case are formed and the TTC is evaluated. Limiting case is formed by increasing the load in small steps till a point after which bus voltages or line loadings start to violate their stability constraints. To improve the system conditions in the limiting case, reactive power optimization and UPFC installation is carried out. The results reflect the improvement in system conditions and total transfer capability margins. Availability of sufficient generator reactive margins is very essential to ensure system’s voltage stability, without which even minor disturbances may lead to catastrophe. The amount of reactive power margin available in a system determines its proximity to voltage instability under normal and emergency conditions. One way of improving the reactive margin of a synchronous generator, is to reduce the real power generation within its MVA ratings. However this real power reduction will affect the real power contract agreements formed while power trading. The real power contracts are not disturbed and the reactive power margins are improved by optimally adjusting the other available reactive controllers, namely, generator exciter, transformer taps and shunt compensators. To have further control on the reactive flows, UPFC device is incorporated at appropriate locations. The thesis discusses how reactive margins are computed and subsequently improved using a reactive power optimization technique and UPFC. Case studies are carried out on typical sample 6bus, 8bus, 10bus, 16bus, 20bus, IEEE 30bus, IEEE 39bus systems, and reallife equivalents of Indian southern grid 24bus, 72bus, 87bus and 205bus systems to illustrate the proposed approaches.