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Periodic Report Summary 2 - GARPUR (Generally Accepted Reliability Principle with Uncertainty modelling and through probabilistic Risk assessment)

Project Context and Objectives:
Power system reliability management aims to maintain power system performance at a desired level, while minimizing the socio-economic costs of keeping the power system at that performance level.
Historically in Europe, network reliability management has been lying on the so-called “N-1” criterion: in case of fault of one relevant element (e.g. one transmission system element, one significant generation element or one significant distribution network element), the elements remaining in operation must be capable of accommodating the new operational situation without violating the network’s operational security limits. Today, the increasing uncertainty of generation due to intermittent energy sources, combined with the opportunities provided e.g. by demand-side management and energy storage, call for imagining new reliability criteria with a better balance between reliability and costs.

Within this context, the GARPUR project designs, develops, assesses and evaluates new reliability criteria to be progressively implemented over the next decades at a pan-European level, while maximizing social welfare. The seven main objectives of GARPUR are:
1. To develop a consistent probabilistic framework for reliability management, covering the definition of reliability, the calculation of reliability criteria, and the formulation of optimization problems expressing the economic costs and the desired target reliability levels at the pan-European level and within each individual control zone.
2. To develop a consistent methodology for the quantitative evaluation of the economic impact on society of different reliability management strategies both at the pan-European level, and within each control zone.
3. To develop a quantification platform able to compare different reliability management strategies in terms of their impact on the social welfare.
4. To ensure the compliance of the developed methodologies with the technical requirements of system development, asset management and power system operation, and to demonstrate the practical exploitability of the new concepts at the pan-European level and in all decision making contexts.
5. To validate the different reliability criteria with the help of pilot tests.
6. To ensure the general acceptance of the proposed methods and tools by all stakeholders affected by the reliability management of the pan-European electric power system.
7. To define an implementation roadmap towards the use of the new reliability management practices.

To ensure progress beyond the state-of-the-art, GARPUR pursues five different aspects by which progress can be ensured and evaluated. These are defined as:
1. Model the spatiotemporal variation of the probabilities of exogenous threats and take into account the actual criticalities of service interruptions in the reliability management.
2. Take into account the increased possibilities of corrective control and its probability of failure in the reliability management.
3. Exploit the flexibility provided by demand-side management and energy storage, to achieve the reliability enhancement given the emergence of decentralized renewable generation.
4. Explicitly model the impact of system development and asset management decisions on the reliability management during operation,
5. Explicitly take into account the consideration of low-probability high-impact events, such as the ones originating from extreme weather conditions, possibly through climate change, or those originating from adverse behaviours of external entities.

Project Results:
WP1 "Revisiting reliability management methodologies"
The literature on power systems reliability has been confronted with the current reliability management approaches, identifying a gap between the existing literature and what is practiced by TSOs. The probabilistic methods proposed are barely used. One important driver to introduce new methods is the need for a better balance between reliability and costs, while lack of required data is found to be one of the main barriers.

WP2 "Development of new reliability criteria for the pan-European electric power system
A mathematical model of reliability management approaches and criteria (RMAC) has been formulated, as a multi-stage stochastic programming problem, a socio-economic objective function, a reliability target, and completed by a “discarding principle” prescribing a level of accuracy, and a “relaxation principle” for situations where the target cannot be reached. Algorithmic implementations have been developed both for real-time and mid-term reliability management. Directions for extending to short- and long-term have been identified, along with the main steps (guidelines) for implementation.

WP3 "Socio-economic assessment of reliability criteria"
A socio-economic impact assessment methodology has been formulated, based on social welfare analysis of the electricity system. It allows quantifying the costs, benefits, and surplus of all stakeholder groups, and details how to calculate interruption costs, TSO costs, producer costs, environmental costs and congestion costs on different time horizons. A mathematical formulation of these surpluses is given for different nodes, generation technologies, consumer types, time of occurrence and duration of interruptions, and pollutants.

WP4 "System development"
An approach has been proposed consisting of: screening of operating states, grid planning, and a 2-step optimisation first identifying the promising target topologies, then defining for each of them the optimal grid development path. The framework takes market aspects, reliability aspects and possible grid investments into account. An important finding is that use of a market tool is crucial in the process of generation credible operating states.

WP5 "Asset management"
The assessment of outage schedules (mid-term) and maintenance policies (long-term) have been addressed, resulting in the development of algorithms based on Monte-Carlo simulations, combined with proxies of system operation and outage scheduling activities. Main modelling topics analysed are load and RES forecasting, influence of the weather on the failure rates, maintenance scheduling, failure rates and outage durations. Theoretical models have been identified to represent the ageing process of the assets, as well as the benefits brought by maintenance.

WP6 "Power system operation"
Reliability assessment algorithms for real-time operation and short-term operational planning have been developed, based on a reliability criterion considering scenarios of the uncertain exogenous parameters and their probability and methods to assess this reliability criterion. The methods are structured around a discarding principle that allows discarding scenarios to make the problem tractable, algorithms to check the reliability criterion, and an indicator of socioeconomic surplus.

WP7 "Development of a quantification platform for reliability criteria"
The quantification platform is aimed at simulating the use of the methodologies brought forward, and comparing them with the current methods in use. A functional description of the quantification platform has been established for both an ideal and a prototype platform, and the prototype is being developed progressively. Currently the prototype is being enhanced in order to allow its use in the context of the pilot tests specified in WP8.

WP8 "Pilot scale validation"
Eight possible pilot tests have been identified and prioritised, covering both pilot tests utilising the prototype quantification platform as well as the "near real-life" pilot tests using adapted versions of the TSO's own tools. Detailed specifications have been written for three high priority pilot tests, and an adjusted second version of the quantification platform prototype GQP is tested on the RTE pilot test. The two near real-life pilot tests are currently under preparation.

WP9 "Recommendations and roadmap for migration"
The analyses of GARPUR results, including feedback from dissemination events, are continuously ongoing. Preparations are also being made for finalizing the recommendations and road map during the last year of the project.

Potential Impact:
It is believed that GARPUR will show that new criteria for reliability management of the pan-European transmission system can and should depart from the N-1 criterion, by using a probabilistic approach that ensures pan-European system reliability while optimizing social welfare. The diagram below summarizes the expected outcomes.

Figure 1: GARPUR outcomes (see attached project summary pdf)

GARPUR develops a comprehensive and coherent probabilistic methodology covering the different TSO activities (system development, asset management, operations). For each studied reliability management alternative, the Quantification Platform links the socio-economic consequences of their implementation. This is mathematically modelled as an optimization problem, based on two consistent frameworks: one for probabilistic reliability management and another for socio-economic impact evaluations. The deployment roadmap for the new reliability criteria will show relevance at the pan-European level for applications by TSOs within the three time horizons.

There will probably be extra investments involved to deploy the probabilistic reliability management framework. Yet the extra benefits of providing adequate levels of reliability may override the required costs as it will be possible to show by the use of the quantification platform. Indeed:
- information technology capable of extensive data processing and network simulations tools make a probabilistic approach to reliability management increasingly realistic.
- in the future TSOs must cope with potentially critical situations due to the massive arrival of stochastic generation, the development of a pan-European electricity market leading to massive cross border exchanges, and the opportunities to leverage new sources of flexibility in the context of operation as well as in the context of long-term planning.

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