Vijay Venu Vadlamudi

Dependability and security-based failure considerations in protection system reliability studies

The reliability of protection systems has a considerable effect on the reliability of supply, and hence appropriate protection system reliability models must be incorporated in power system reliability studies. These studies assume increasing prominence, especially in the wake of influx of smart grid technologies, making it imperative to handle the accompanying failure dependencies in detail. This paper presents the results of one such related investigation carried out to incorporate the impact of transmission line failure modes on account of various protection system response scenarios on supply reliability indices. In addition to the basic frequency and duration indices, indices such as annual power interrupted, annual energy not supplied, and annual interruption costs are computed, built on a minimal cut set based approach. The approach presented circumvents the need for complex Markov models to include protection system reliability considerations. An illustrative case study is employed to draw attention to the impact of identified comprehensive failure scenarios in protection and control equipment on power system reliability. Comparisons are made with an existing simplified method, and also with a case where protection system reliability is assumed to be perfect. The results bring forward the emphasis to be placed on initiatives to include the study of impact of reliability of protection systems on reliability of supply.

Effects of dependent and common mode outages on the reliability of bulk electric system - Part II: Outage data analysis

A companion paper (Part I) presents the basic concepts of dependent and common mode outages, the causes for their origins in the bulk electric system (BES) and the subsequent effects from a reliability perspective. This paper describes the practical outage data collection efforts in vogue in North America and parts of Europe, with particular emphasis on outage data statistics corresponding to dependent and common mode outages. The goal is to eventually be able to obtain standard, representative reliability indices for typical transmission elements such as lines and transformers from the available outage data.

Research on Common-Mode and Dependent (CMD) Outage Events in Power Systems: A Review

The purpose of this paper is to present a review of some fundamental concepts and practical applications in the area of common-mode and dependent (CMD) outage events in power systems. The paper is a result of ongoing activity carried out by the Probability Applications for Common and dependent Mode Events (PACME) Working Group (WG) of the Reliability, Risk and Probability Applications Subcommittee. The PACME WG was formed in 2010 to review, advance, and present the research and practical applications in the area of CMD outage events. This paper presents state-of-the-art in research, modeling, and applications of CMD outage events in power system planning and operation. Issues considered include: data monitoring and collection, and probabilistic modeling and evaluation in the planning, and operation of power generation and transmission systems. Additionally, some results obtained from outage data statistics corresponding to CMD outage events in systems such as Generating Availability Data System, Transmission Availability Data System, and Canadian Electrical Association are presented.

Effects of dependent and common mode outages on the reliability of bulk electric system - Part I: Basic concepts

This paper is the first part of a two-part paper based on the ongoing activity carried out by the Task Force (TF) of the Working Group (WG) on Probability Applications for Common Mode Events (PACME) in electric power systems under the Reliability, Risk and Probability Applications (RRPA) Subcommittee. The primary objectives of this work are to (1) review and discuss the basic definitions of dependent, common-mode and cascading outage events, (2) identify the major causes of common-mode, dependent and cascading outages, (3) recognize the effects of protection system failures and misoperations on the Bulk Electric System (BES), and (4) assess the impact of weather related outages and extreme events on the performance of the BES. The scope of Part I is limited to the basic concepts on common-mode and dependent outages. The overall goal of the two papers is to assist the wider efforts within the industry in practically assessing the effects of dependent and common-mode outages on the reliability of BES.

Impact of protection system reliability on power system reliability: A new minimal cutset approach

In order to capture the effect of dependent failures that could arise due to the various transmission protection system response scenarios on power system reliability, complex Markov models or fault trees combined with event trees are typically employed in the predictive reliability studies. A unique approach utilizing minimal cutsets (MC) and the approximate methods of system reliability evaluation, dispensing with the assumption of perfect protection and control, was recently postulated to obtain various power system reliability indices. The approach was basic in that it was applicable to single circuit meshed transmission systems, where only MCs up to a maximum order of two could be handled. However, the parallel structure of transmission lines in multi-circuit meshed transmission systems, in addition to resulting in possible higher order critical transmission line MCs, creates unique topological dependencies among the backup protection system coordination schemes. In this paper, a comprehensive MC approach to capture the impact of protection system reliability on power system reliability is presented, covering all such consequent dependencies. An illustrative sample case study is used to explain the salient features of the proposed methodology.

Impact of substation configuration on protection system failure propagation and its effect on reliability of supply

Relatively fewer studies exist in literature on including the complex effects of transmission protection system related failure dependencies in the reliability prediction models. Usage of extensive Markov models has been usually advocated to capture the impact of protection system reliability on power system reliability. A new analytical method which makes use of approximate methods of system reliability evaluation has been recently proposed by us, which circumvents the need for Markov models. It is a unique minimal cutset-based approach for single circuit meshed transmission systems, where several basic and load/energy oriented reliability indices are obtained. The objective of this paper is to extend the procedure to examine the impact of substation configurations on protection system failure dependency propagation and its effect on bulk load point reliability indices. Preliminary investigations show a marked impact of employing a station configuration with simplified bus representation, especially in multi circuit meshed transmission systems, on the resulting reliability indices. The results of the proposed methodology are demonstrated on a suitably modified four bus illustrative test system, for cases with and without the consideration of protection system failures for a realistic station configuration.

Interconnector participation in capacity mechanisms: A new de-rating approach

In countries with Capacity Mechanisms in place, where Explicit Interconnector Participation model is to be used, one of the key market design questions to be answered is how the amount of interconnector capacity that is allowed to participate in the auctions should be determined. This paper argues for an interconnector capacity de-rating approach. In order for the de-rating factor to be representative of stochasticity inherent in the system, the concept of Interconnector Effective Load Carrying Capability is postulated in this paper. A method with probabilistic basis that allows for converting the name-plate capacity of a transmission line connecting two areas into a de-rated capacity is proposed. The proposed probabilistic methodology takes into account the technical availability of the line and captures the impact of simultaneous or co-incident scarcity. A simple case-study is presented to exemplify the proposed principle and methodology.

Enhanced method for reliability of supply assessment - an integrated approach

A comprehensive analysis of reliability of electricity supply to end users requires a unique set of models, methods and tools. Of special significance are long term power market models for predicting future operating states (generation and load patterns) and more detailed network simulation models for analysing consequences of contingencies. This paper describes an integrated approach for reliability of supply analysis, assessing reliability and interruption costs down to the specifics of different kinds of end users at different delivery points in the network model. Furthermore, the effects of power system protection, temporal variation of parameters, and corrective actions as part of the consequence analysis, are taken into account in the presented integrated approach. The results are illustrated through a case study on a realistic hydro dominated four-area meshed test system.

On improving data and models on corrective control failures for use in probabilistic reliability management

One of the most pressing concerns in the investigation of new probabilistic reliability criteria pertains to the data required as input to the evolving probabilistic models. This paper discusses an area of failure data collection that has been overlooked in power system reliability studies: corrective control actions. Background information is provided on the need for evolution of data collection systems in this context. Further, steps that can be taken to build a database of parameters necessary for modelling corrective actions are provided, to be useful in assessing system behaviour from a probabilistic reliability management perspective. Modelling of corrective control actions using event trees is illustrated. Throughout, the various challenges foreseen in the building of corresponding databases and models are outlined.

Reliability-Centric Studies in Smart Grids: Adequacy and Vulnerability Considerations

There are diverse visions on how to go about achieving reliability, energy conservation, and efficiency with environmental compliance through the inter-disciplinary integration of information and communication technologies (ICT) and power system technologies to facilitate the modernization of grids. The paradigm of smart grid has been brought forward and is being continually improvised to cater to the energy demands of the twenty-first century. However, the term “reliability” used in invariably defining and outlining the characteristic features of smart grids seems to be in a generic context, and more often than not qualitative. The aim of this chapter is to appraise the challenges presented by the envisioned transformation towards Smart grids in terms of capturing the anticipated quantitative reliability benefits and the growing need for allied reliability-related studies.