Contingency Selection Method Research Articles

A Risk-Based Contingency Selection Method for SPS Applications

In current power system operations, transmission networks have been operated at their limits much more frequently and for much longer periods of time. Special protection systems (SPS) are attractive for increasing transmission capacity in a competitive market, but the installation costs and system reliability issues are important. In this letter, a risk-based method is proposed to take the uncertainty of contingency occurrence and impacts into account to provide an essential set of contingency cases for SPS implementation.

Contingency selection method for on‐line small signal stability monitoring

AbstractTo make greater use of existing electric power transmission facilities, security assessment utilizing on‐line data is thought to be one of the effective measures that can be taken. To realize on‐line assessment of postfault small signal stability for a number of supposed contingencies, it is effective to identify severe contingencies to be analyzed with a precise assessment program, such as the S‐method. We developed a contingency selection method that has two indices for selection.One of the indices is postfault eigenvalue estimation based on second‐order approximation of the eigenvalue change in response to system matrix change, which is effective for relatively weak nonlinear eigenvalue change. The other one is the Nonlinearity index, which indicates the strength of nonlinearity eigenvalue change. It is effective in detecting strong nonlinear eigenvalue changes that cannot be estimated correctly by second‐order approximation.Calculation results with IEEJ Bulk Power System Models show that the proposed method can effectively decrease the number of contingencies that must be analyzed by the precise Small Signal Analysis method. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(4): 20–27, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10186

オンライン定態安定度監視のための事故選択スクリーニング手法の開発

To make more use of existing electric power transmission facilities, security assessment utilizing on-line data is thought to be one of the effective measures that can be taken. To realize on-line assessment of post-fault small signal stability for a number of supposed contingencies, it is effective to pick out severe contingencies to be analyzed with precise assessment program, e.g. S-method. We developed contingency selection method that has two indexes for selection. One of the indexes is post-fault eigenvalue estimation based on 2nd approximation of eigenvalue change for system matrix change, which is effective for relatively weak non-linear eigenvalue change. The other one is Non-linearity Index that indicates the strength of non-linearity of eigenvalue change. It is effective to detect the strong non-linear eigenvalue change that can not be estimated correctly by the 2nd approximation estimation. Calculation results with IEEJ Bulk Power System Models show that the proposed method can effectively decrease the number of contingencies that have to be analyzed with precise Small Signal Stability Analysis method.

CONTEX: An expert system for contingency selection

In this paper a novel approach for contingency selection is proposed, which chooses the presumable critical contingencies of a power system. To avoid the usual misclassifications of purely algorithmic contingency selection methods the expert system CONTEX incorporates operator knowledge into the contingency selection process. Test results reported here show that the proposed approach is reliable and efficient for use in power network control centers.

New techniques for secure power system operation

This paper describes a security algorithm that incorporates load flows, contingency selection, AC outage studies and security control. The load flow method is based on the superdecoupled load flow method of Haley and Ayres, which gives rapid and exact load flow solutions. Separate contingency selection methods for real power flow and voltage security analyses have been developed. For real power analysis the line overload contingency selection technique of Stott et al. has been adopted, but for voltage security analysis a new voltage contingency selection technique has been developed. Critical outages selected from the contingency selection functions are analysed in detail with AC outage simulations of line and generator outages. For security control a range of feasible corrective actions are provided which inclued phase shifter control, generation rescheduling and/or load shedding to alleviate the line overload problem and transformer taps to adjust the bus voltage deviations. New and fast line overload alleviation techniques have been developed by using injections at the terminating buses of the overloaded line without having to compute the sensitivity and Jacobian line flow matrices. The proposed security algorithm has been validated by testing on several standard test systems.

Critical Review of Branch Contingency Selection Methods

A number of different types of branch contingency selection methods has been devised over the last decade, while some have been available for over 30 years. Each method has its strengths and weaknesses and needs to be evaluated for a particular application. This paper critically reviews branch contingency selection methods. All techniques are first discussed in detail. This discussion is followed by an evaluation table containing uniform attributes by which the methods can be compared. A brief description of spafsity techniques and possible future developments closes the paper.

Realistic power system security algorithm

The paper presents a security algorithm which consists of the superdecoupled loadflow technique for loadflow solution, outage studies, contingency selection and line overload alleviation. A superdecoupled loadflow method with a distributed slack busbar has been applied to line and generator outage studies as well as for line overload alleviation. The accuracy and reliability of the line and generator outage contingency selection method, as previously developed by comparison of its ranking results with the correct ranking of AC outage simulation, has been investigated. A fast computation technique in real power line overload alleviation by generation scheduling and/or load shedding has been proposed by using injections at the terminating busbars of the overloaded line. These injections are determined by the amount of overload only without having to compute the sensitivity and Jacobian line flow matrices and pseudoinverse of the product of these matrices. The proposed algorithm has been validated in tests on the IEEE 24 busbar test system.

Reactive Power Considerations in Automatic Contingency Selection

On-line steady-state security analysis requires the evaluation of the effects of a large number of possible contingencies on a power system. Almost all contingency analysis programs have had to rely on a list of selected contingencies to be studied. The brute force approach of testing all contingencies every time an evaluation of the system performance is needed, becomes prohibitive due to its computational burden. A particularly attractive technique is to utilize a fast, approximate method to select the few contingencies that actually affect the security of the power system and then analyze only these cases in more detail. The contingency ranking and selection methods presented in the literature have all ranked outage cases on the basis of transmission line overloads. This limits the usefulness of these technqiues as contingencies that cause only voltage problems are totally overlooked. This paper shows that there is little correlation between the contingencies that produce line overloads and those that result in unacceptable voltage profiles, further establishing the need for a contingency selection method that is also voltage sensitive. Such a method, using the first iteration of an AC power flow, is presented. It is shown that the method meets both the speed and accuracy requirements for on-line use.