Reliability Importance Measures-Based Analysis of Substation Communication Network

Importance analysis of noncoherent systems is limited, and is generally inaccurate because all measures of importance that have been developed are strictly for coherent analysis. This paper considers the probabilistic measure of component importance developed by Birnbaum (1969). An extension of this measure is proposed which enables noncoherent importance analysis. As a result of the proposed extension the average number of system failures in a given interval for noncoherent systems can be calculated more efficiently. Furthermore, because Birnbaum's measure of component importance is central to many other measures of importance; its extension should make the derivation of other measures possible.

Substation communication network (SCN) provides real-time, high-speed, and reliable data transmissions for the advanced monitoring and control functionalities, which are facing increasing cyberspace threats and attacks. Efficient threat perception and cyber situational awareness are essential to enhance secure and reliable SCN operations. This article explores multiscale SCN traffic pattern characteristics with holistic network traffic, separated network traffic for included devices (especially IoT devices) and separated network traffic of certain types of protocol. The proposed online traffic-oriented SCN traffic anomaly detection and cyber situational awareness models are designed for the network anomalies and cyber-attacks that could cause network traffic pattern variations. We leverage a fractional autoregressive integration moving average (FARIMA)-based dynamic threshold model to detect abnormal traffic patterns without sophisticated computations or deep packet inspection. The SCN real-time operation conditions are timely quantified through the statistical methods with the alliance of SCN topology and protocols. The cyber situational awareness model is further carried out to evaluate the most affected protocol and security risks of various devices in SCN using Grubbs’ test. The experiment results are carried out based on a real 110-kV intelligent power substation. The numerical results confirm the comparative low mean square error (MSE) and low complexity of the online traffic characterization when forecasting holistic network traffic and separated network traffics. Furthermore, the timely and quantified cybersecurity risk analysis is conducted based on the SCN traffic with varying scales to detect cyberspace threats and identify the high-risk SCN devices and the most affected protocol.

We introduce in this paper a new measure of component importance, called redundancy importance, in coherent systems. It is a measure of importance for the situation in which an active redundancy is to be made in a coherent system. This measure of component importance is compared with both the (Birnbaum) reliability importance and the structural importance of a component in a coherent system. Various models of component redundancy are studied, with particular reference to k/out / of / n systems, parallel-series systems, and series-parallel systems.

The main purpose of this paper is to study the communication protocol IEC61850 (Communication Networks and Systems in Substations) to develop of practical fast transmission modes in direct trip schemes, using communication functions to implement protection, control and condition monitoring functions under IEC61850 protocol to complete devices data integration in substation automation system. The way of direct trip schemes can provide fast communication speed to stable power system operation in case of suddenly events occasions. The messages interchange via GOOSE (Generic Object Oriented Substation Event) application is based on the IEC61850 communication protocol to implement fast direct trip modes. It is found that the interaction communication of direct trip schemes among various protective relays can be achieved by the IEC61850 protocol based on GOOSE application to approach system stabile operation under occasionally events.

智能变电站在电力系统中处于重要地位，为了满足电力系统的要求，电力通信网结构不断地进行优化，大量引进通信领域新技术，使得电力通信网越来越复杂。影响变电站通信安全的因素日益增加，变电站通信网络安全这一问题变的日益复杂。本文以智能变电站的通信网络为基础，对智能变电站通信网络的发展历程进行简要介绍，分析比较几种通信技术的优缺点，针对变电站信息安全面对的威胁以及现阶段管理现状、管理制度等在实际运行中存在的问题进行深入讨论，全面研究分析了变电站面临的信息安全问题。 Intelligent Substation in the power system is an important factor. In order to meet the power system require- ments, the system constantly optimizes power communication network structures, including massive introduction of new communications technologies, making electric power communication network more complex than ever. Factors affecting the substation communication safety are increasing. Substation communication network security problems become more complex. In this paper, intelligent substation communication networks based on intelligent substation communication network development process are briefly described, and the advantages and disadvantages of several communication technologies are analyzed and compared . In the end of the article, this paper comprehensive analyzed substation informa- tion system threats, present management situation and management system in actual operation.

In the last decades there have been great advances in electronic, information and communication technologies. Up to date, any of these advances have been implemented in electrical systems, but some difficulties have been encountered, particularly regarding to the integration of intelligent electronic devices from different manufactures into a centralized system. With the aim of solving the above mentioned problem, the standard IEO 61850 was developed to specify communication networks in substations. In addition to control and protection functions, the information model created around IEO 61850 series can help the development of other applications related with electrical monitoring systems. Monitoring can be used to achieve a variety of benefits for utilities, including maintenance prediction, failure prevention, active control, improved commissioning tests and more accurate end of life assessments. Examples of application that could be highly benefited by the adoption of IEC 61850 as standard for communications in the power electrical industry are power quality monitoring and condition based maintenance.In this paper, the new standard IEC61850 and the new opportunities that it can offer to the electrical industry are presented. Firstly, a brief presentation of IEC61850 and the main benefits it provides are described. Finally, a more detailed description of the possibilities that IEC61850 can offer in the field of power quality monitoring and condition based maintenance (CBM) is highlighted.

The paper presents a comparison of four widely used reliability importance measures in order to identify their appropriateness for the identification of the most critical system components for replacement planning; specifically when using Non-sequential Monte Carlo method. These importance measures are Improvement Potential, Structural Importance, Criticality Importance, and Fussell-Vesely Importance. The four reliability importance measures were calculated for each system component (power transformer in this particular study) and then components were ranked separately based on each measure. Then, the components were replaced, one by one starting from the most critical, to establish the relationship between the replacement according to each ranking and the overall system reliability. The study was performed on a realistic transmission network containing 154 transformers. The results of the paper proved that Improvement Potential is the most appropriate importance measure for replacement planning.

Power system automation and communication standards are spearheading the power system transition towards a smart grid. IEC 61850 is one such standard, which is widely used for substation automation and protection. It enables real-time communication and data exchange between critical substation automation and protection devices within digital substations. However, IEC 61850 is not cyber secure. In this paper, we demonstrate the dangerous implications of not securing IEC 61850 standard. Cyber attacks may exploit the vulnerabilities of the Sampled Values (SV) and Generic Object-Oriented Substation Event (GOOSE) protocols of IEC 61850. The cyber attacks may be realised by injecting spoofed SV and GOOSE data frames into the substation communication network at the bay level. We demonstrate that such cyber attacks may lead to obstruction or tripping of multiple protective relays. Coordinated cyber attacks against the protection system in digital substations may cause generation and line disconnections, triggering cascading failures in the power grid. This may eventually result in a partial or complete blackout. The attack model, impact on system dynamics and cascading failures are veri ed experimentally through a proposed cyber-physical experimental framework that closely resembles real-world conditions within a digital substation, including Intelligent Electronic Devices (IEDs) and protection schemes. It is implemented through Hardware-in-the-Loop (HIL) simulations of commercial relays with a Real-Time Digital Simulator (RTDS).

Infrastructure networks are critical backbones of urban society that support virtually every economic and societal activity. Recent events have shown that these systems are susceptible to natural and man-made hazards such as earthquakes, hurricanes, and terrorist attacks, and have the potential risk of creating cascading failures due to their interdependent nature. Therefore, analyzing the vulnerability of these complex interacting infrastructures under potential hazards is critical for the development of risk mitigation strategies and effective response and recovery. To assess the seismic risk on the infrastructure, non simulation-based methods have the merit of rapid risk assessment for infrastructures and the associated decision making, because they are efficient in estimating sensitivities and conditional probabilities which are often used for identifying critical components. This article presents a non simulation-based method to assess the system reliability of complex interdependent infrastructure networks under seismic hazards. Also proposed are methods to compute importance measures to gauge the relative contribution of components to system reliability. A case study is presented to demonstrate the proposed approach that can efficiently estimate the reliability of a network system, the effect of interactions between two networks, and the importance measures of components.

Importance measure is an index for estimating the importance of an individual component or a group of components in a reliability system. So far, the importance measures for components in stochastic reliability systems have been investigated. In order to calculate the importance of a component or a group of components in an uncertain reliability system, this paper proposes a new concept of importance index. Some formulas are given to calculate the importance index of a component and a group of components in an uncertain reliability system. Then, some special types of uncertain reliability systems such as uncertain series, parallel, parallel-series, series-parallel, bridge, and k-out-of-n systems are studied.

Feeder Automation is an important link of Distribution System Automation (DSA). As a key competent in a DSA, the improvement of the communication and data processing performance of a Feeder Terminal Unit (FTU) is especially important. This paper designs a GOOSE message receiving and sending process through analyzing the communication mechanism of Object Oriented Substation Event, combining the requirements of Feeder System Automation (FSA) on FTU based on the substation communication network and system protocol IEC 61850, and achieves GOOSE message communication process and GOOSE message application data processing functions on the basis of UC-OSII real-time operating system and RTL8019 network controller. It has been applied in FSAs presently, its communication delay measured is within 4ms which has reached the expected performance requirement.

With the increasing deployment of Distributed Energy Resources (DERs) in the distribution system, DERs presents many challenges for smooth and stable operation of the grid. For the effective management of DERs extensive communication between different components of DER and distribution system is required. To standardize the communication methods and modeling of logical nodes required for Intelligent Electronic Devices (IEDs) in DERs, data modeling of DERs is issued in IEC 61850-7-420 standard. This paper has contributed communication modeling of Green Energy Resources (GERs) and other DERs, modeling of messages exchanged among different IEDs with regard to their optimum structure & size and a Substation Communication Network (SCN) topology. End to End (ETE) time delay performance of the designed communication configuration architecture is presented using OPtimized Network Engineering Tool (OPNET). The dynamic performance result in the SCN has demonstrated the successful communication configuration for integrating the DERs in distribution system.

Traditional reliability importance measures have been successfully extended from binary-state models to multi-state models. The calculation of these measures typically relies on the true reliabilities of components. In reality, however, the true values of component reliabilities are usually unknown, and they are generally approximated by their estimates generated from testing or field failure data. The accuracy of the estimates is limited by the available data. Research on uncertainty importance measures (UIMs) has emerged on this account to rank components based on their potentials to reduce the uncertainty about the estimated system reliability. The UIMs of components for binary-state models are well studied, but there is a lack of studies dedicated to multi-state models. In this paper, the reliability estimator and the corresponding uncertainty (characterized by the variance estimator) are derived for multi-state systems with structures such as serial, parallel, bridge, and their more complex combinations. The derivation process utilizes multinomial reliability testing and the universal generating function method. With the help of the derived estimators, we extend uncertainty importance research to multi-state models through a newly defined variance-based measure. Examples are provided to demonstrate the proposed ideas.

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