Power system reliability evaluation considering cyber-malfunctions in substations

This paper presents the concept of overall power system reliability evaluation using an educational test system. The paper extends an existing test system by developing the necessary distribution and subtransmission networks. The extended test system has all the main facilities, such as generation, switching stations, transmission, sub-transmission and radial distribution networks found in a practical system. The test system, is however, sufficiently small that students can analyze it using hand calculations or by developing small computer programs to fully understand the reliability models and evaluation techniques. Overall power system reliability evaluation is concerned with providing acceptable customer service. This is an important concern in today's electric utility environment. This should therefore be an essential element in teaching power system reliability evaluation at either the graduate or undergraduate level, The extended test system presented in this paper and the concepts presented assist in satisfying this requirement.

FACTS technologies can have major positive impacts on power system reliability performance and the actual benefits obtained can be assessed using suitable models and practice. Emerging techniques for composite power system reliability evaluation mainly focus on conventional generation and transmission facilities. In this paper, improvement of Reliability in composite electric power system is examined by incorporating Unified Power Flow Controller (UPFC). Two test systems, Reliability Test System (RTS) and Roy Billinton Test System (RBTS) are considered to show major improvement in reliability. A state space reliability model of multi-module UPFC has been developed and incorporated in the system. Load point & System indices performances are presented to examine the impact of UPFC on the composite electric power system reliability. Investigation results show a significant improvement in the Load point & system indices when utilizing UPFC.

Reliability and economic evaluation of power system with renewables: A review

Three-parameter interval number theory and its application in power system reliability evaluation

Adverse weather, such as hurricanes, can have severe effects on power system reliability. Incorporating weather effects in power system reliability evaluation has drawn more and more attention in recent years. In past decades, many methods have been proposed to evaluate power system reliability considering weather effects. Some of the earliest methods used the two-state weather model. These have been later expanded into multi-state weather model, regional weather model (RWM) and statistical regression method. In this paper, a fuzzy expert system (FES) is proposed and is combined with RWM to assess hurricane impact on the reliability parameters of transmission lines. Firstly, according to the computation requirements the composite system is partitioned into different regions. Then, the FES maps the nonlinear relationship between the hurricane parameters (indicator of hurricane severity) and the increment multipliers of failure rates (IMFR) of the transmission lines in different regions. In this step, the possible case that transmission lines traverse adjacent regions is investigated by using weighted average method (WAM). Finally, the results obtained by using the proposed method can be used in analytical or simulation method to evaluate composite system reliability considering hurricane impact. The proposed method is applied to the IEEE reliability test system (RTS). The implementation demonstrates that the proposed method is effective and efficient and the FES is convenient to construct.

High reliability of railway power systems is one of the essential criteria to ensure quality and cost-effectiveness of railway services. Evaluation of reliability at system level is essential for not only scheduling maintenance activities, but also identifying reliability-critical components. Various methods to compute reliability on individual components or regularly structured systems have been developed and proven to be effective. However, they are not adequate for evaluating complicated systems with numerous interconnected components, such as railway power systems, and locating the reliability critical components. Fault tree analysis (FTA) integrates the reliability of individual components into the overall system reliability through quantitative evaluation and identifies the critical components by minimum cut sets and sensitivity analysis. The paper presents the reliability evaluation of railway power systems by FTA and investigates the impact of maintenance activities on overall reliability. The applicability of the proposed methods is illustrated by case studies in AC railways.

This paper proposes an efficient method to identify the importance of transmission network components from the network’s reliability perspective. The proposed method is able to reveal the weak points of the network and can be employed as useful tool by power system planners to identify where investments should be made to increase the overall system reliability. The proposed approach has two main stages, including evaluation of the network contingency states and a sensitivity analysis which shows the link between reliability of each component and overall system reliability. Unlike the similar methods in this area and with the help of two reasonable simplifications, the proposed method can be employed to real transmission networks with acceptable computational burden. The proposed method is implemented on two test systems including the IEEE Reliability Test System (IEEE RTS) and the Roy Billinton Test System (RBTS). The obtained results demonstrate the efficiency of the proposed approach.

Secure operation of protective intelligent electronic devices (IEDs) has been recognized as a crucial issue for power grids. By gaining access to substation IEDs, intruders can severely disrupt the operation of protection systems. This paper develops an analytical reliability assessment framework for quantifying the impacts of the hypothesized integrity attacks against protection systems. Petri net models are used to simulate possible intrusion scenarios into substation networks. The cyber network model is constructed from firewall, intrusion prevention system (IPS), and password models, which are three types of defense mechanisms for protecting substation networks. In this paper, two main types of attacker actions on protective devices are recognized: 1) sending breaker opening commands through IED connections; and 2) changing IED settings. In this regard, a multistate Markov model is proposed for identifying possible consequences of cyber attacks on the protective devices. In addition, this model captures the essential remedial actions that are taken after a successful cyber attack against target equipment. Subsequently, an analytical approach based on the introduced Markov model is proposed for assessing power system reliability. The proposed framework is implemented on the modified IEEE reliability test system, and its effectiveness is demonstrated through extensive case studies.

Power systems has been subjected to significant upgrades in terms of structure and capacity. Reliability evaluation of composite power systems has surfaced as an essential step in operation and planning stages of the modern power system. It is an effective tool to investigate the ability of power systems to supply customers with reliable power service. The purpose of this review is to enhance the knowledge of reliability studies conducted on composite power systems by providing a critical and systematic review. This work investigates peer-reviewed articles published between 2007 and 2017 in three reliable databases. The findings reveal that the reliability of composite power systems has received considerable attention over the last few years. Secondly, investigation studies demonstrated a crucial role in verifying the impact of adopting new technologies. Third, studies on this topic have been intensively conducted in Asia, which highlights the promising sectors in these regions. However, researchers have generally focused on developing several aspects (e.g., evaluation speed and wind power integration) at the expense of others (e.g., realistic studies and other renewable energy resources). The lack of practical applications is evident in the surveyed publications. These findings imply a potential incoordination between the needs of the real applications and researchers’ tendencies. Future reliability evaluation scholars are advised to consider the findings of this systematic review including concentrating on insufficiently covered topics and enhance the coordination among the efforts devoted in this area.

Reliability of an electrical power system plays a vital role in providing continuous power supply to consumers with greater quality. The power demand is increasing day by day due to the increased population, modern society and are seeking highly reliable power. The assessment of reliability is very difficult due to the presence of large number of components and complex power system network con-figurations. This paper address a novel useful step by step algorithm for the assessment of average power availability at load buses us-ing the concept of modified Petri nets with conditional probability. The proposed algorithm is very efficient and can applicable to any number of the bus system. The proposed algorithm is tested with Roy Billiton practical example, IEEE 6 bus, IEEE 14 bus and IEEE RTS-96 bus system. The obtained results are validated by Monte Carlo simulation method, Classical Node elimination method and mod-ified minimal cut set method.

Large-scale adoption of gas-fired power plants (GPPs) significantly accelerates the integration of power systems and natural gas systems (NGSs). Because the operation of NGS has a significant impact on the reliability of power system, it is important to simultaneously evaluate the reliabilities of power system and NGS. Moreover, due to the stochastic failures and various operating characteristics of components, the integrated gas and power systems (IGPS) considering multiple states can be viewed as a multi-state system. Therefore, a multi-state model is proposed for reliability evaluation of IGPS based on universal generating function (UGF) techniques. First, a framework is proposed to evaluate the reliability of NGS: multi-state models for different components in the NGS are developed as the corresponding UGFs. These UGFs are aggregated utilizing the gas flow calculation operator to obtain the multi-state model of NGS. Moreover, a gas-to-power calculation operator is developed to convert the multi-state model of gas injection at each node to the power output models of GPPs in power system. In this manner, the impacts of NGS could be incorporated into the reliability evaluation of power system. Furthermore, nodal reliability indices for both the NGS and the power system are proposed to evaluate the reliability performances of IGPS. The proposed methods are validated using the integrated gas and power test system.

Similar to other cities worldwide, the increasing amounts of short-circuit current in Bangkok (Thailand) and the vicinity areas are becoming higher than the interrupting capacity (IC) of circuit breakers. To cope with the problem, the Electricity Generating Authority of Thailand (EGAT) has come up with the solutions of network reconfiguration, e.g. bus splitting and transmission line disconnecting. These solutions help reduce effectively the amounts of short-circuit currents by increasing the equivalent system impedance. However, bus splitting and transmission line disconnecting tend to decrease the system reliability. One of the alternative approaches, the installation of high-voltage direct current (HVDC) can help reduce the amounts of short-circuit currents, while the system reliability is maintained. Therefore, this paper mainly presents the reliability evaluation method of the systems with HVDC installation, which requires AC/DC power flow calculation. To avoid system constraint violation, generation redispatch, load shedding, and DC power flow control are executed. The Monte Carlo simulation is used to repeatedly evaluate the system reliability until convergence. The proposed method is tested in (i) the IEEE Reliability Test System 79 (RTS79) to confirm the correctness of reliability evaluation and (ii) the system of EGAT Bangkok including its vicinity areas to show the readiness for real implementation. Comparison of reliability indices among all solutions of short-circuit current reduction is presented and discussed. The results show that the proposed method is effective and the HVDC installation can increase the system reliability, depending on its installation location and capacity. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A novel approach for the construction of the equivalent two-state models for base load generating units with derated states is suggested in order to reduce the computational burden in composite power system reliability (adequacy) evaluation. The proposed equivalent is conceived in such a way to preserve the invariance of the failure probability of the generation system taken alone, under assumption that the network effects upon the generating units models are slight and can be ignored. The equivalent model suggested has been successfully tested and compared with the EFOR based model for the IEEE RT System.

With large-scale wind farms integrated into power systems, the computational requirements for reliability evaluation of composite power systems are increasing. This paper introduces a new concept of dynamic orthogonal list, which is a form of multiple failure retrievals to avoid repeatedly calling the optimal power flow (OPF) program in the stage of state evaluation. An existing algorithm of cross-entropy (CE) method was developed to deal with the rare events in sampling. The major contribution of CE is to achieve convergence faster and reduce the number of samples, thus shortening the consuming time in the stage of sampling. This paper proposes a fast reliability evaluation process which combines the CE method with dynamic orthogonal list (CE-DOL), comprehensively improving the computational efficiency of Monte Carlo simulation (MCS). The proposed method is tested on a modified IEEE-RTS 79 system. In addition, for comparison purposes, the efficiencies of MCS, CE, and CE-DOL are estimated in the cases of different system adequacies. It is shown that, in range of certain reliability level, the proposed method is much more efficient compared with the CE method. Finally, the applicability of different methods is analyzed under different system reliability levels.

<p>Technique to evaluate probability of occurrence of selected contingencies of 6 Bus Roy Billinton Test System (RBTS) and IEEE 9 Bus system by Markov modelling is presented in this paper. Obtained probabilities for selected contingencies are validated by comparing with binomial distribution based probabilities. Load flow analysis and performance index based contingency ranking of total elements of 6 bus RBTS and IEEE 9 Bus systems is simulated by Power System Simulation for Engineers (PSSE) software. Novel reliability evaluation technique which unify contingency ranking with Markov modeling is proposed for RBTS and extended to IEEE 9 Bus system. Accuracy, completeness and simple to implement are salient features of proposed novel reliability evaluation method. Reliability of RBTS and IEEE 9 Bus systems can be improved by incorporating Flexible Alternating Current Transmission Systems (FACTS) device. Improvement in the reliability and economic revenue of RBTS and IEEE 9 Bus systems due to Unified Power Flow Controller (UPFC) incorporation is evaluated.</p>