scholarly journals Integrated Risk Assessment for Robustness Evaluation and Resilience Optimisation of Power Systems after Cascading Failures

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 2028
Author(s):  
Jesus Beyza ◽  
Jose M. Yusta
Keyword(s):  
Power Systems ◽  
Circuit Breaker ◽  
Recovery Process ◽  
Daily Basis ◽  
Operating Conditions ◽  
Power Lines ◽  
Mixed Integer ◽  
Electrical Network ◽  
Overload Capacity ◽  
The Impact

Power systems face failures, attacks and natural disasters on a daily basis, making robustness and resilience an important topic. In an electrical network, robustness is a network’s ability to withstand and fully operate under the effects of failures, while resilience is the ability to rapidly recover from such disruptive events and adapt its structure to mitigate the impact of similar events in the future. This paper presents an integrated framework for jointly assessing these concepts using two complementary algorithms. The robustness model, which is based on a cascading failure algorithm, quantifies the degradation of the power network due to a cascading event, incorporating the circuit breaker protection mechanisms of the power lines. The resilience model is posed as a mixed-integer optimisation problem and uses the previous disintegration state to determine both the optimal dispatch and topology at each restoration stage. To demonstrate the applicability of the proposed framework, the IEEE 118-bus test network is used as a case study. Analyses of the impact of variations in both generation and load are provided for 10 simulation scenarios to illustrate different network operating conditions. The results indicate that a network’s recovery could be related to the overload capacity of the power lines. In other words, a power system with high overload capacity can withstand higher operational stresses, which is related to increased robustness and a faster recovery process.

scholarly journals Analysis of Internal Overvoltages in Transformer Windings during Transients in Electrical Networks

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2644 ◽  
Author(s):  
Jakub Furgał ◽  
Maciej Kuniewski ◽  
Piotr Pająk
Keyword(s):  
Power Systems ◽  
Electromagnetic Waves ◽  
Power Transformer ◽  
Electrical Power ◽  
Operating Conditions ◽  
Electromagnetic Transients ◽  
Electrical Network ◽  
Electrical Networks ◽  
Insulation Systems ◽  
The Impact

Due to the increasing requirements for the reliability of electrical power supply and associated apparatus, it is necessary to provide a detailed analysis of the overvoltage risk of power transformer insulation systems and equipment connected to their terminals. Exposure of transformer windings to overvoltages is the result of the propagation condition of electromagnetic waves in electrical networks and transformer windings. An analysis of transformer winding responses to transients in power systems is of particular importance, especially when protection against surges by typical overvoltage protection systems is applied. The analysis of internal overvoltages in transformers during a typical transient related to switching operations and selected failures is of great importance, particularly to assess the overvoltage exposure of insulation systems in operating conditions. The random nature of overvoltage phenomena in electrical networks implies the usage of computer simulations for the analysis of overvoltage exposures of electrical devices in operation. This article presents the analysis of the impact of transient phenomena in a model of a medium-voltage electrical network during switching operations and ground faults on overvoltages in the internal insulation systems of transformer windings. The basis of the analysis is simulations of overvoltages in the windings, made in the Electromagnetic Transients Program/Alternative Transients Program (EMTP/ATP) using a model with lumped parameters of transformer windings. The analysis covers the impact of the cable line length and the ground fault resistance value on internal overvoltage distributions.

scholarly journals Overvoltage Impact on Internal Insulation Systems of Transformers in Electrical Networks with Vacuum Circuit Breakers

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6380
Author(s):  
Marek Florkowski ◽  
Jakub Furgał ◽  
Maciej Kuniewski ◽  
Piotr Pająk
Keyword(s):  
Power Systems ◽  
Circuit Breaker ◽  
Dielectric Strength ◽  
Electrical Network ◽  
Electrical Networks ◽  
Circuit Breakers ◽  
Zero Crossing ◽  
Vacuum Circuit Breaker ◽  
Insulation Systems ◽  
The Impact

Vacuum circuit breakers are increasingly used as switching apparatus in electric power systems. The vacuum circuit breakers (VCBs) have very good operating properties. VCBs are characterized by specific physical phenomena that affect overvoltage exposure of the insulation systems of other devices. The most important phenomena are the ability to chop the current before the natural zero crossing, the ability to switch off high-frequency currents, and the rapid increase in dielectric strength recovery. One of the devices connected directly to vacuum circuit breakers is the distribution transformer. Overvoltages generated in electrical systems during switching off the transformers are a source of internal overvoltages in the windings. The analysis of the exposure of transformers operating in electrical networks equipped with vacuum circuit breakers is of great importance because of the impact on the insulation systems of switching overvoltages (SO). These types of overvoltages can be characterized by high maximum values and atypical waveforms, depending on the phenomena in the circuit breaker chambers, system configuration, parameters of electrical devices, and overvoltage protection. Overvoltages that stress the internal insulation systems are the result of the windings response to overvoltages at transformer terminals. This article presents an analysis of overvoltages that stress the transformer insulation systems, which occur while switching off transformers in systems with vacuum circuit breakers. The analysis was based on the results of laboratory measurements of switching overvoltages at transformer terminals and inside the winding, in a model medium-voltage electrical network with a vacuum circuit breaker.

scholarly journals Indices to Assess the Integration of Renewable Energy Resources on Transmission Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Alexandros I. Nikolaidis ◽  
Francisco M. Gonzalez-Longatt ◽  
C. A. Charalambous
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
Renewable Energy Sources ◽  
Ghg Emissions ◽  
Electrical Network ◽  
Transmission Network ◽  
Renewable Energy Resources ◽  
Continuous Increase ◽  
And Control ◽  
The Impact

The continuous increase on the penetration levels of Renewable Energy Sources (RESs) in power systems has led to radical changes on the design, operation, and control of the electrical network. This paper investigates the influence of these changes on the operation of a transmission network by developing a set of indices, spanning from power losses to GHG emissions reduction. These indices are attempting to quantify any impacts therefore providing a tool for assessing the RES penetration in transmission networks, mainly for isolated systems. These individual indices are assigned an analogous weight and are mingled to provide a single multiobjective index that performs a final evaluation. These indices are used to evaluate the impact of the integration of RES into the classic WSCC 3-machine, 9-bus transmission network.

scholarly journals Mixed Integer Quadratic Programming Based Scheduling Methods for Day-Ahead Bidding and Intra-Day Operation of Virtual Power Plant

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1410 ◽  
Author(s):  
Rakkyung Ko ◽  
Daeyoung Kang ◽  
Sung-Kwan Joo
Keyword(s):  
Quadratic Programming ◽  
Power Systems ◽  
Power Plants ◽  
Power Grids ◽  
Mixed Integer ◽  
Virtual Power ◽  
Integer Quadratic Programming ◽  
Virtual Power Plants ◽  
Mixed Integer Quadratic Programming ◽  
The Impact

As distributed energy resources (DERs) proliferate power systems, power grids face new challenges stemming from the variability and uncertainty of DERs. To address these problems, virtual power plants (VPPs) are established to aggregate DERs and manage them as single dispatchable and reliable resources. VPPs can participate in the day-ahead (DA) market and therefore require a bidding method that maximizes profits. It is also important to minimize the variability of VPP output during intra-day (ID) operations. This paper presents mixed integer quadratic programming-based scheduling methods for both DA market bidding and ID operation of VPPs, thus serving as a complete scheme for bidding-operation scheduling. Hourly bids are determined based on VPP revenue in the DA market bidding step, and the schedule of DERs is revised in the ID operation to minimize the impact of forecasting errors and maximize the incentives, thus reducing the variability and uncertainty of VPP output. The simulation results verify the effectiveness of the proposed methods through a comparison of daily revenue.

scholarly journals Fixed-speed and Variable-speed Pumped Storage Dispatch Model in Power Systems with High Renewable Penetration

2018 ◽  
Vol 38 ◽  
pp. 04014
Author(s):  
Bo Yuan ◽  
Jin Zong ◽  
Zhicheng Xu
Keyword(s):  
Power Systems ◽  
Linear Optimization ◽  
Operating Conditions ◽  
Economic Life ◽  
Mixed Integer ◽  
Variable Speed ◽  
Operating Characteristics ◽  
Storage Unit ◽  
New Energy ◽  
Pumped Storage

According to different operating characteristics of pumped storage fixed speed unit and variable speed unit, a joint dispatching model of pumped storage unit and other types of units based on mixed integer linear optimization is constructed. The model takes into account the operating conditions, reservoir capacity, cycle type and other pumped storage unit constraints, but also consider the frequent start and stop and the stability of the operation of the unit caused by the loss. Using the Cplex solver to solve the model, the empirical example of the provincial power grid shows that the model can effectively arrange the pumping storage speed and the dispatching operation of the variable speed unit under the precondition of economic life of the unit, and give full play to the function of peak shaving and accommodating new energy. Because of its more flexible regulation characteristics of power generation and pumping conditions, the variable speed unit can better improve the operating conditions of other units in the system and promote the new energy dissipation.

A Dual-speed Induction Motor as a Source of Electrical Hazard in Operating Conditions of Coal Mine Process Support Areas

2021 ◽  
pp. 145-152
Author(s):  
E.V. Denisova ◽  
K.N. Marenich ◽  
E.S. Dubinka
Keyword(s):  
Induction Motors ◽  
Operating Conditions ◽  
Electrical Network ◽  
Electrical Safety ◽  
Stator Windings ◽  
Process Support ◽  
Energy Flows ◽  
Safety Parameters ◽  
The Impact ◽  
Dual Speed

Hazardous states of the mine zonal electrical network are caused by the reversed energy flows of induction motors of the energy-consuming equipment in the run-down mode after the power supply is switched off. The electromotive force (EMF) induced in the powered-off stator windings of the dual-speed motors due to the transformer effect also pose a danger of electric shock. The paper presents a methodology and the results of studying the formation of induced EMFs in the powered-off stator windings of dual-speed induction motors, including the run-down mode and the functions that impact on the electromagnetic parameters. Analysis of the impact degree of these induced EMFs on the electrical safety parameters as part of the mine zonal electrical network is presented.

Assessment of Tesla Turbine Performance for Small Scale Rankine Combined Heat and Power Systems

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Van P. Carey
Keyword(s):  
Power Systems ◽  
Residential Buildings ◽  
Rankine Cycle ◽  
Combined Heat And Power ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Manufacturing Cost ◽  
Turbine Design ◽  
The Impact

For solar Rankine cycle combined heat and power systems for residential buildings and other small-scale applications (producing 1–10 kWe), a low manufacturing cost, robust, and durable expander is especially attractive. The Tesla-type turbine design has these desired features. This paper summarizes a theoretical exploration of the performance of a Tesla turbine as the expander in a small-scale Rankine cycle combined heat and power system. A one-dimensional idealized model of momentum transfer in the turbine rotor is presented, which can be used to predict the efficiency of the turbine for typical conditions in these systems. The model adopts a nondimensional formulation that identifies the dimensionless parameters that dictate performance features of the turbine. The model is shown to agree well with experimental performance data obtained in earlier tests of prototype Tesla turbine units. The model is used to explore the performance of this type of turbine for Rankine cycle applications using water as a working fluid. The model indicates that isentropic efficiencies above 0.75 can be achieved if the operating conditions are tailored in an optimal way. The scalability of the turbine design, and the impact of the theoretical model predictions on the development of solar combined heat and power systems are also discussed.

Towards the Implementation of Optimal Train Loading Plan in the Athens-Thessaloniki Freight Services

2017 ◽  
Vol 8 (3) ◽  
pp. 39-53
Author(s):  
Athanasios Ballis ◽  
Fillipos Karapetis ◽  
Theocharis Ballis
Keyword(s):  
Information System ◽  
Daily Basis ◽  
Operating Conditions ◽  
Mixed Integer ◽  
Integer Optimization ◽  
Container Transport ◽  
Railway Infrastructure ◽  
Mixed Integer Optimization Model ◽  
Pragmatic Aspects ◽  
Train Loading

The main goal of train loading optimization is the proper assignment of loading units onto the wagons, taking under consideration numerous factors like the maximum axle load restrictions, the condition of the railway infrastructure, the operating conditions, safety regulations etc. The typical expression of the problem is usually formulated under one of the two following assumptions: (a) the commodity load is predefined or (b) the number and type of wagons is fixed. The current work describes the steps that were followed and enabled the analysis, optimization and integration of the train loading plan into the information system that supports the new railway service of TRAINOSE for containers transport on the Athens – Thessaloniki line. This new service, named iCS, was launched in December 2013 and ever since operates on a daily basis. The work includes a literature review, a mention of the pragmatic aspects that influence container transport and train loading plan, the presentation of the heuristic which is implemented in the information system of iCS service, a validation process against a mixed integer optimization model and finally concludes with the proposed solution for the iCS wagon loading problem.

scholarly journals Assessing the Impact of Cybersecurity Attacks on Power Systems

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 725 ◽  
Author(s):  
Athanasios Dagoumas
Keyword(s):  
Power Systems ◽  
Power System ◽  
Linear Trend ◽  
Operating Cost ◽  
Energy System ◽  
Operating Conditions ◽  
System Stability ◽  
System Cost ◽  
System Operator ◽  
The Impact

Cybersecurity is an emerging challenge for power systems, as it strongly affects their reliability and the whole energy system cost. The paper uses several Unit Commitments (UC) models, applying different methods to tackle renewables’ uncertainty. The selected power system is IEEE RTS 96. The UC models are used to assess the impact of different cybersecurity threats. The focus is to assess their impact on the total operating cost and the power grid adequacy to handle them. The comparison between the UC models shows that more robust UC models lead to higher total operating costs. The cost, unit dispatching, and energy mix evolution have a non-linear trend, depending on the power system characteristics and the cyberattacks types. However, the paper provides evidence of considerable price signals in the case of the examined cyberattacks. Each Transmission System Operator (TSO) should examine combinations of cyberattacks and operating conditions to identify crucial cases for system stability and power system cost operation. The applied methodology would also require substantial developments or supplementary approaches to assess cyberthreats at the distribution level.

scholarly journals A Data-Driven Approach for Online Inter-Area Oscillatory Stability Assessment of Power Systems Based on Random Bits Forest Considering Feature Redundancy

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1641
Author(s):  
Songkai Liu ◽  
Dan Mao ◽  
Tianliang Xue ◽  
Fei Tang ◽  
Xin Li ◽  
...  
Keyword(s):  
Feature Selection ◽  
Power Systems ◽  
Operating Conditions ◽  
Accurate Estimation ◽  
Stability Assessment ◽  
Real Time System ◽  
Operating Data ◽  
The Impact ◽  
System Operating ◽  
Bus System

To utilize the rapidly refreshed operating data of power systems fully and effectively, an integrated scheme for inter-area oscillatory stability assessment (OSA) is proposed in this paper using a compositive feature selection unit and random bits forest (RBF) algorithm. This scheme consists of offline, update, and online stages, and it can provide fast and accurate estimation of the oscillatory stability margin (OSM) by using the real-time system operating data. In this scheme, a compositive feature selection unit is specially designed to realize efficient feature selection, which can significantly reduce the data dimensionality, effectively alleviate feature redundancy, and provide accurate correlation information to system operators. Then, the feature set consisting of the selected pivotal features is used for the RBF training to build the mapping relationships between the OSM and the system operating variables. Moreover, to enhance the robustness of the scheme in the face of variable operating conditions, an update stage is developed. The effectiveness of the integrated scheme is verified on the IEEE 39-bus system and a larger 1648-bus system. Tests of estimation accuracy, data processing speed, and the impact of missing data and noise data on this scheme are implemented. Comparisons with other methods reveal the superiority of the integrated scheme. In addition, the robustness of the scheme to variations in system topology, distribution among generators and loads, and peak and minimum load is studied.

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