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This paper presents the findings of the research aimed at developing computer models to determine the operating conditions in electric power systems (EPSs) feeding DC and AC railway substations. The object of the research is an EPS with a predominant traction load whose high-voltage power lines are connected to transformer and converter substations with 3 kV and 27.5 kV traction networks. The supply network includes 110 kV and 220 kV power lines. The EPS operating parameters are calculated based on the decomposition of the system into alternating and direct current segments. Calculations are performed for the fundamental frequency and high harmonic frequencies. The modeling technique is universal and can be used to determine the operating parameters and power quality indices for any configuration of an EPS and various designs of traction networks. With this technique, one can solve numerous additional problems, such as calculating the processes of ice melting in traction networks and power lines, determining electromagnetic field strengths, and assessing the heating of power line wires and catenary suspensions. The results obtained show that the voltages on the current collectors are within acceptable limits for all AC and DC electric locomotives. The levels of asymmetry on the 110 and 220 kV tires of traction substations (TP) do not exceed the normally permissible values. The values of the asymmetry coefficients for DC TP are tenths of a percent. With an increase in the size of traffic and in post-emergency conditions caused by the disconnection of communication between one of the support substations and the EPS, the asymmetry indicators on the 220 kV buses of AC substations may exceed the permissible limits. Phase-controlled reactive power sources can be used to reduce them. The analysis of the results of the determination of non-sinusoidal modes allows us to formulate the conclusion that the values of harmonic distortion go beyond the normative limits. Passive and active filters of higher harmonics can be used to normalize them. Calculations of thermal modes of traction transformers show that the temperatures of the most heated points do not exceed acceptable values. [ABSTRACT FROM AUTHOR]

This research looks into a systemic impact factor (SIF) as a complement to enhance the prescriptive capabilities of electric substations with the objective of improving the reliability and robustness of components. As electrical networks become increasingly complex, prescriptive analytical tools are needed to ensure sustained power delivery. The purpose is to develop a framework for evaluating failure effects, including both direct and indirect effects on substation performance. The study makes use of a multi-criteria method that incorporates safety, environment protection, reliability, and network robustness among other factors like SAIDI and SAIFI to determine the actual impact of failures to make better decisions. The methodology is illustrated using a criticality model, and a case study, focusing on operational contexts of the failure. The SIF proposal provides a better understanding of different aspects and their contribution, when a failure event occurs under a given operational context. This factor improves maintenance management by identifying critical equipment and projecting the effects of failure through a specific operation network. A case study in an electrical substation estimates the SIF for each element used in daily operations to improve support services and increase substation dependability. Therefore, SIF is an essential factor to consider in electrical substations for their maintainability and reliability evaluation. [ABSTRACT FROM AUTHOR]

Electric substations (ESS) are important facilities that must operate even under contingency to guarantee the electrical system's performance. To achieve this goal, the Brazilian national electricity system operator establishes that alternating current (AC) auxiliary systems of ESS must have, at least, two power supplies, and in the case of failure of these sources, an emergency generator (EG) must at least supply energy to the essential loads. In order to improve the availability of auxiliary systems, a microgrid with other sources, such as photovoltaic (PV) systems and Battery Energy Storage Systems (BESS), can be an alternative. In this case, an economical optimization of the PV/BESS system must be addressed considering the costs associated with the installation and maintenance of equipment, and the gains from the credits generated by the photovoltaic system in the net metering scheme. In this paper, the size of the BESS system was determined to supply energy to the load of auxiliary systems of an ESS, as well as a PV system to achieve a null total cost. Furthermore, multi-objective optimization using the genetic algorithm technique was employed to optimize the size of the hybrid PV/BESS to minimize the investment cost and time when the demand was not met. Simulations under different scenarios of contingency were allowed to obtain the Pareto frontier for the optimal sizing of a PV/BESS system to supply energy to AC auxiliary systems in an ESS under contingency. [ABSTRACT FROM AUTHOR]

One option to avoid range issues for electrified heavy vehicles, and the large individual batteries for each such vehicle, is to construct electric road systems (ERS), where vehicles are supplied with electricity while driving. In this article, a model has been developed that calculates the cost for supplying an ERS with electricity from a regional grid to a road in the form of cables and substations, considering the power demand profile for heavy transport. The modeling accounts for electric losses and voltage drop in cables and transformers. We have used the model to exhaustively compute and compared the cost of different combinations of substation sizes and locations along the road, using a European highway in West Sweden as a case study. Our results show that the costs for building an electricity distribution system for an ERS vary only to a minor extent with the location of substations (10% difference between the cheapest cost and the average cost of all configurations). Furthermore, we have varied the peak and average power demand profile for the investigated highway to investigate the impact of a specific demand profile on the results. The results from this variation show that the sum of the peak power demand is the most important factor in system cost. Specifically, a 30% change in the peak power demand for the road has a significant impact on the electricity supply system cost. A reduction in the geographical variation of power demand along the road has no significant impact on the electricity distribution system cost as long as the aggregated peak power demand for all road segments is held constant. The results of the work are relevant as input to future work on comparing the cost–benefit of ERS with other alternatives when reducing CO2 from road traffic—in particular from heavy road traffic. [ABSTRACT FROM AUTHOR]

In Poland, rail transport is powered by the electric system with the use of traction substations that supply the electric traction with DC voltage of 3 kV. The necessity to change the alternating voltage to the constant and changing loads of the substation cause the electric traction to be a recipient, generating a number of disturbances to the network. These disturbances affect the quality of electricity in the power system from which traction substations are supplied, and the power quality in auxiliary and non-traction lines. This article analyzes the measurements of power quality indicators recorded at selected points of the traction substation system. The parameters characterizing the power quality were recorded, among others, in the main lines supplying traction substations, non-traction lines and auxiliary circuits. The presented article is the first in a series of publications related to the assessment of the impact of DC electric traction on the power system. The recorded data will be the basis for computer simulations defining, inter alia, the impact of power supply conditions for traction substations on the power system and to propose methods of reducing disturbances generated by a dynamically changing substation load. [ABSTRACT FROM AUTHOR]

This article presents a new method for the estimation of active power losses based on a "field" approach, i.e., on the theory of the electromagnetic field and the theory of propagation of electromagnetic waves in a dielectric medium. Electromagnetic waves are assumed to transmit energy from the traction substation to electric rolling stock through the airspace of the inter-substation zone (i.e., not through the wires of the traction network) and meet electrically conductive surfaces on their way. The waves are partially reflected from the surfaces and partially penetrate them, thus creating thermal losses, the determination of which is the main task of this article. The analytical expressions for specific losses of active power are obtained by solving the system of Maxwell's equations. Calculations of specific power losses in the catenary, rails, roofs, and bottoms of carriages and electric locomotives are performed. Power losses in carriages and electric locomotives are found to be at least 7%. A comparative assessment of the magnitude of total power losses of different types obtained by the "field" and "circuit" approaches is provided, which has established that "conditional" losses correspond to losses in rails, train carriages, and electric locomotives. [ABSTRACT FROM AUTHOR]

A constant worldwide growing load stress over a power system compelled the practice of a reactive power injection to ensure an efficient power network. For this purpose, multiple technologies exist in the knowledge market out of which this paper emphasizes the usage of the flexible alternating current transmission system (FACTS) and presents a comparative study of the static var compensator (SVC) with the static synchronous compensator (STATCOM), inducted in a real electric substation. The aim is to improve the power factor (PF) and power quality and to encounter reliably extreme conditions. A 220 kV electric substation was opted for the analysis, and both the static and dynamic conditions were observed with the help of a power system analysis tool termed PowerFactory-DIgSILENT. Multiple aspects were investigated via software simulations to assess the performance of the aforementioned FACTS devices, such as the voltage profile evaluation via the load flow analysis method (LFA), the harmonic response via the power quality and harmonic analysis tool, and the short-circuit response via the RMS simulation tool. The outcomes were verified and compared with permissible values included in the universal standards, such as IEC and IEEE. The superiority of the STATCOM over the SVC was proven in light of the simulative results. [ABSTRACT FROM AUTHOR]

Composite insulators are widely used in modern power systems to provide electrical insulation and mechanical support for transmission lines and substations. However, the insulation strength will decrease greatly under the combined conditions of ice-covering and contamination, and icing flashovers may take place under these serious conditions. In this paper, AC flashover tests of different artificially ice-covered 220 kV composite insulators were carried out in a multi-function artificial climate chamber under energized ice accumulation conditions. The test results indicate that, with the increasing of ice thickness, the flashover voltages decrease and tend to saturation. The icing flashover voltages can be increased by adding booster sheds, but excessive booster sheds can lead to lower flashover voltages under heavy icing conditions. The voltage distributions of the iced insulators were measured using experimental methods. The results show that, the air gaps withstand most of the applied voltage. The zinc oxide (ZnO) resistors that are contained in the insulators can influence the voltage distributions of the iced insulators, but have little affect on the icing flashover voltages. The work done in this paper can provide reference for the design and type selection of outdoor composite insulators in cold climate regions. [ABSTRACT FROM AUTHOR]

Most electrical substations are remotely monitored and controlled by using Supervisory Control and Data Acquisition (SCADA) applications. Current SCADA systems have been significantly enhanced by utilizing standardized communication protocols and the most prominent is the IEC 61850 international standard. These enhancements enable improvements in different domains of SCADA systems such as communication engineering, data management and visualization of automation process data in SCADA applications. Process data visualization is usually achieved through Human Machine Interface (HMI) screens in substation control centres. However, this visualization method sometimes makes supervision, control and maintenance procedures executed by engineers slow and error-prone because it separates equipment from its automation data. Augmented reality (AR) and mixed reality (MR) visualization techniques have matured enough to provide new possibilities of displaying relevant data wherever needed. This paper presents a novel methodology for visualizing process related SCADA data to enhance and facilitate human-centric activities in substations such as regular equipment maintenance. The proposed solution utilizes AR visualization techniques together with standards-based communication protocols used in substations. The developed proof-of-concept AR application that enables displaying SCADA data on the corresponding substation equipment with the help of AR markers demonstrates originality and benefits of the proposed visualization method. Additionally, the application enables displaying widgets and 3D models of substation equipment to make the visualization more user-friendly and intuitive. The visualized SCADA data needs to be refreshed considering soft real-time data delivery restrictions. Therefore, the proposed solution is thoroughly tested to demonstrate the applicability of proposed methodology in real substations. [ABSTRACT FROM AUTHOR]

Corona discharge could be a serious hazard to the outdoor insulation of a high-voltage (HV) system and also is an important detection issue for insulation status diagnosis. In this study, a double-helix-ultrasonic-array (DHUA) sensor was developed for corona positioning, which showed a good sensitivity to the ultrasonic signal originating from corona discharge and a satisfied directional response in static beam patterns. Based on the matting-based image fusion method, the acoustic intensity matrix was fused to a visual scene in real-time. This ultrasonic visualization technology was then evaluated with a simulation test and performed in a real air insulated substation (AIS), and showed a satisfied performance in terms of sensitivity and spatial location resolution. [ABSTRACT FROM AUTHOR]

In this paper, we propose a very effectively filtering approach (EFA) to enhance network traffic performance for high-availability seamless redundancy (HSR) protocol in smart grids. The EFA combines a novel filtering technique for QuadBox rings (FQR) with two existing filtering techniques, including quick removing (QR) and port locking (PL), to effectively reduce redundant unicast traffic within HSR networks. The EFA filters unicast traffic for both unused terminal rings by using the PL technique and unused QuadBox rings based on the newly-proposed FQR technique. In addition, by using the QR technique, the EFA prevents the unicast frames from being duplicated and circulated in rings; the EFA thus significantly reduces redundant unicast traffic in HSR networks compared with the standard HSR protocol and existing traffic filtering techniques. The EFA also reduces control overhead compared with the filtering HSR traffic (FHT) technique. In this study, the performance of EFA was analyzed, evaluated, and compared to that of the standard HSR protocol and existing techniques, and various simulations were conducted to validate the performance analysis. The analytical and simulation results showed that for the sample networks, the proposed EFA reduced network unicast traffic by 80% compared with the standard HSR protocol and by 26-62% compared with existing techniques. The proposed EFA also reduced control overhead by up to 90% compared with the FHT, thus decreasing control overhead, freeing up network bandwidth, and improving network traffic performance. [ABSTRACT FROM AUTHOR]

The growing environmental challenge of electrical energy systems has prompted a substantial increase in renewable energy generation. Such generation systems allow for significant reduction of CO2 emissions compared with a traditional fossil fuel plant. Furthermore, several improvements in power systems network configuration and operation combined with new technologies have enabled reduction of losses and energy demand, thus contributing to reduction of CO2 emissions. Another environmental threat identified in electrical networks is the leaking of insulating sulfur hexafluoride (SF6) gas used in electrical gas insulated substations (GIS) and equipment. Because of its Global Warming Potential (GWP) of nearly 24,000 and its long life in the atmosphere (over 3000 years), SF6 gas was recognized as a greenhouse gas at the 1997 COP3; since then its use and emissions in the atmosphere have been regulated by international treaties. It is expected that as soon as an alternative insulating gas is found, SF6 use in high-voltage (HV) equipment will be banned. This paper presents an overview of the key research advances made in recent years in the quest to find eco-friendly gases to replace SF6. The review reports the main properties of candidate gases that are being investigated; in particular, natural gases (dry air, N2 or CO2) and polyfluorinated gases especially Trifluoroiodomethane (CF3I), Perfluorinated Ketones, Octafluorotetra-hydrofuran, Hydrofluoroolefin (HFOs), and Fluoronitriles are presented and their strengths and weaknesses are discussed with an emphasis on their dielectric properties (especially their dielectric strength), GWP, and boiling point with respect to the minimum operating temperature for HV power network applications. [ABSTRACT FROM AUTHOR]

This paper presents a systematic framework to evaluate the performance of conservation voltage reduction (CVR) by determining suitable substations for CVR in operations planning. Existing CVR planning practice generally only focuses on the energy saving aspect without taking other underlying attributes into account, i.e., network topology and reduced voltage effects on other substations. To secure the desired operating reserve and avoid any adverse impacts, these attributes should be considered for implementing CVR more effectively. This research develops a practical decision-making framework based on the analytic hierarchy process (AHP) to quantify several of the aforementioned attributes. Candidate substations for CVR deployment are prioritized such that performances are compared in terms of power transfer distribution factor (PTDF), voltage sensitivity factor (VSF), and CVR factor. In addition, to meet a specified reserve requirement, an integer programming approach is adopted to select potential substations for CVR implementations. Case studies for a Korean electric power system under diverse operating conditions are performed to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Power devices intended for high-voltage systems must be tested according to international standards, which includes the short-time withstand current test and peak withstand current test. However, these tests require very special facilities which consume huge amounts of electrical power. Therefore, mathematical tools to simulate such tests are highly appealing since they allow reproducing the electromagnetic and thermal behavior of the test object in a fast and economical manner. In this paper, a three-dimensional finite element method (3D-FEM) approach to simulate the transient thermal behavior of substation connectors is presented and validated against experimental data. To this end, a multiphysics 3D-FEM method is proposed, which considers both the connector and the reference power conductors. The transient and steady-state temperature profiles of both the conductors and connector provided by the 3D-FEM method prove its suitability and accuracy as compared to experimental data provided by short-circuit tests conducted in two high-current laboratories. The proposed simulation tool, which was proven to be accurate and realistic, may be particularly useful during the design and optimization phases of substation connectors since it allows anticipating the results of mandatory laboratory tests. [ABSTRACT FROM AUTHOR]

In this paper, it is argued that some low-level aspects of the usual IEC 61850 mapping to Ethernet are not well suited to microgrids due to their dynamic nature and geographical distribution as compared to substations. It is proposed that the integration of IEEE time-sensitive networking (TSN) concepts (which are currently implemented as audio video bridging (AVB) technologies) within an IEC 61850 / Manufacturing Message Specification framework provides a flexible and reconfigurable platform capable of overcoming such issues. A prototype test platform and bump-in-the-wire device for tunneling horizontal traffic through AVB are described. Experimental results are presented for sending IEC 61850 GOOSE (generic object oriented substation events) and SV (sampled values) messages through AVB tunnels. The obtained results verify that IEC 61850 event and sampled data may be reliably transported within the proposed framework with very low latency, even over a congested network. It is argued that since AVB streams can be flexibly configured from one or more central locations, and bandwidth reserved for their data ensuring predictability of delivery, this gives a solution which seems significantly more reliable than a pure MMS-based solution. [ABSTRACT FROM AUTHOR]

High-availability seamless redundancy (HSR) is a protocol for Ethernet networks that provides duplicated frames with zero recovery time in the event of any network component's failure. It is suited for applications that demand high availability and a very short time-outs such as substation automation systems (SAS). However, HSR generates excessive unnecessary unicast frames and spreads them throughout connected-ring networks, whether or not the destination node exists in network's rings. This unnecessary redundant traffic causes high bandwidth consumption, resulting in degradation of network performance. In this paper, we introduce a novel approach for filtering and reducing HSR unicast traffic in connected-ring networks, called "filtering HSR traffic" (FHT). The purpose of FHT is to filter HSR unicast traffic and remove circulated traffic for all rings in connected-ring networks. Therefore, FHT significantly reduces network unicast traffic in connected-ring networks. The traffic performance of FHT has been analyzed, evaluated, and compared to that of standard HSR protocol and the port locking (PL) approach. Various simulations were conducted to validate the traffic performance analysis. Analytical and simulation results showed that, for our sample network, FHT reduced network unicast traffic by about 82% compared with standard HSR and by about 56% compared with the PL approach, thus freeing up network bandwidth and improving network traffic performance. [ABSTRACT FROM AUTHOR]

The high-availability seamless redundancy (HSR) protocol, a potential candidate for substation automation system (SAS) networks, provides duplicated frame copies of each sent frame, with zero fault-recovery time. This means that even in the case of node or link failure, the destination node will receive at least one copy of the sent frame. Consequently, there is no network operation down time. However, the forwarding process of the QuadBox node in HSR is not smart and relies solely on duplication and random forwarding of all received frames. Thus, if a unicast frame is sent in any closed-loop network, the frame copies will be spread through most of all the links in both directions until they reach the destination node, which inevitably results in significant, unnecessary network traffic. In this paper, we present an algorithm called the dual virtual paths (DVP) algorithm to solve such an HSR excessive traffic issue. The idea behind our DVP algorithm is to establish automatic DVP between each HSR node and all the other nodes in the network, except for the QuadBox node. These virtual paths will be used for DVP unicast traffic transmission, rather than using the standard HSR transmission process. Therefore, the DVP algorithm results in less traffic, because there is no duplication or random forwarding, contrary to standard HSR. For the sample networks selected in this paper, the DVP algorithm shows more than a 70% reduction in network traffic and about an 80% reduction in the discarded traffic compared to the standard HSR protocol. [ABSTRACT FROM AUTHOR]

A distribution system was designed and operated by considering unidirectional power flow from a utility source to end-use loads. The large penetrations of distributed generation (DG) into the existing distribution system causes a variety of technical problems, such as frequent tap changing problems of the on-load tap changer (OLTC) transformer, local voltage rise, protection coordination, exceeding short-circuit capacity, and harmonic distortion. In view of voltage regulation, the intermittent fluctuation of the DG output power results in frequent tap changing operations of the OLTC transformer. Thus, many utilities limit the penetration level of DG and are eager to find the reasonable penetration limits of DG in the distribution system. To overcome this technical problem, utilities have developed a new voltage regulation method in the distribution system with a large DG penetration level. In this paper, the impact of DG on the OLTC operations controlled by the line drop compensation (LDC) method is analyzed. In addition, a generalized determination methodology for the DG penetration limits in a distribution substation transformer is proposed. The proposed DG penetration limits could be adopted for a simplified interconnection process in DG interconnection guidelines. [ABSTRACT FROM AUTHOR]

The different locations of the equipment in urban distribution substations (DSSs) and the location of inlet holes and outlet holes usually result in different ventilation effect, which means the power consumed by any ventilating devices present is different. In this paper the temperature field distribution in an urban distribution substation with different locations of the equipment in the substation was calculated first, then factors influencing the temperature field distribution were investigated, and the influence of the different factors was analyzed. When the distance between the apparatus and walls exceeds 3 m, the change of the temperature in the DSS is very small. Therefore considering the floor area of the DSS, 3 m is the best value of the distance between the apparatus. With the change of the environment temperature or the velocity of the ventilation fans, the maximum temperature in the DSS or apparatus will change. Hence an energy saving ventilation strategy is proposed in the paper, and an intelligent cooling control system is developed, which can modify the velocity of the ventilation fans according to the environment temperature, and thus realize energy savings. [ABSTRACT FROM AUTHOR]

Offshore and coastal wind power is one of the fastest growing industries in many areas, especially those with shallow coastal regions due to the preferable generation conditions available in the regions. As with any expanding industry, there are concerns regarding the potential environmental effects which may be caused by the installation of the offshore wind turbines and their associated infrastructure, including substations and subsea cables. These include the potential impacts on the biological, physical and human environments. This review discusses in detail the potential impacts arising from offshore wind farm construction, and how these may be quantified and addressed through the use of conceptual models. It concludes that while not environmentally benign, the environmental impacts are minor and can be mitigated through good siting practices. In addition, it suggests that there are opportunities for environmental benefits through habitat creation and conservation protection areas. [ABSTRACT FROM AUTHOR]

This paper focuses on the evaluation of the electric shock hazard accompanying earth faults in a non-effectively earthed medium-voltage (MV) electrical power network. This hazard depends on the duration and value of the fault current. While the fault current depends on several factors, the most important is the neutral point earthing method. The value of the fault current affects the earthing-electrode voltage value, being the basis for the assessment of electric shock hazard in MV/LV substations. The earthing-electrode voltage is also influenced by the resistance of the substation earthing, which in practice is random. Therefore, an original statistical evaluation method for assessing the electric shock hazard has been developed and presented in this paper. It is based on a statistical model of the MV/LV substation earthing resistance, worked out on the basis of experiments and measurements in real electrical power networks. This method can be used for the determination of statistical distributions of earthing-conductor voltages in real electrical power networks, and on this basis, the MV/LV substations with rates of electric shock hazard that are too high can be indicated. This also makes it possible to determine the longest permissible fault current interruption times or the highest permissible earthing resistances for specific substations. This method is also applicable when selecting the neutral point earthing method. The developed method was used in all of the above proposed areas by performing calculations on a model of a real 15 kV network with the neutral point earthed by a resistor. This analysis proves the practicability of the method both at the stage of designing power networks, and when a change in the neutral point earthing method in existing networks is being considered. Particularly valuable is also the statistical model of an earthing electrode resistance, developed on the basis of measurements in 2408 MV/LV substations, which may also be applicable in the future studies. [ABSTRACT FROM AUTHOR]

This article deals with options for how to express the luminous flux from outdoor electrical substations of the electric transmission system. Processing of the models of light emissions before and after refurbishment of lighting systems was motivated by setting out rules for the design and erection of refurbished lighting systems in outdoor electrical substations, which are most commonly built in inhabited rural areas with low luminance of the background. The proposed model and calculations are based on requirements of international standards and recommendations for lighting of outdoor workplaces as well as on internal regulations of the ČEPS (Czech Transmission System Operator). These requirements are implemented in real electrical substations and lighting models that are extended by the calculation space of the software goniophotometer. The software goniophotometer was used to evaluate light distribution characteristics of entire electric stations in various situations. This article assesses the impact of different lighting systems installed at electrical substations from the perspective of both direct and total luminous flux directed to the upper hemisphere. It takes into account three outdoor electrical substations (420 kV) of a transmission network and their lighting systems before and after refurbishment. The aim of this article is to determine to what extent the electrical substations contribute to emissions of luminous flux to the upper hemisphere. Results from calculations on models show reduced radiation to the upper hemisphere up to 52.3% after refurbishment of obsolete lighting systems, although total installed flux actually increased due to a change in the ratio of direct and reflected luminous flux after refurbishment of lighting systems. [ABSTRACT FROM AUTHOR]

The adoption of Virtual Reality (RV) technologies in prototype design and process revision has contributed to multiple industry areas. Nonetheless, the development of VR systems for engineering is a complex task, as it involves specialized teams handling low-level code development. Given these problems, the goal of this study is presenting a methodology for designing VR, through an Authoring System based on Computer-Aided Design (CAD). The presented methodology provides an easy integration of electric power substation floor plans and Virtual Reality software (VRS), as well as three-dimensional and symbol modeling conventions. Centralized software architecture was developed, composed of the CAD Editor, input manager and VRS. The methodology was evaluated through a case study applied to the conception (elaboration) of electric power substations (EPS) as part of a Research and Development (R&D) project for training and field assets supervision. The results demonstrated visual precision and high integrity in elaboration of a VR environment from the CAD floor plan. This work also presents a comparative analysis between manual conception and the Authoring System. [ABSTRACT FROM AUTHOR]

The IEC 61850 communication standard is getting popular for application in electric power substation automation. This paper focuses on the potential application of the IEC 61850 generic object-oriented substation event (GOOSE) protocol in the AC microgrid for adaptive protection. The focus of the paper is to utilize the existing low-voltage ride through characteristic of distributed generators (DGs) with a reactive power supply during faults and communication between intelligent electronic devices (IEDs) at different locations for adaptive overcurrent protection. The adaptive overcurrent IEDs detect the faults with two different preplanned settings groups: lower settings for the islanded mode and higher settings for the grid-connected mode considering limited fault contributions from the converter-based DGs. Setting groups are changed to lower values quickly using the circuit breaker status signal (XCBR) after loss-of-mains, loss-of-DG or islanding is detected. The methods of fault detection and isolation for two different kinds of communication-based IEDs (adaptive/nonadaptive) are explained for three-phase faults at two different locations. The communication-based IEDs take decisions in a decentralized manner, using information about the circuit breaker status, fault detection and current magnitude comparison signals obtained from other IEDs. However, the developed algorithm can also be implemented with the centralized system. An adaptive overcurrent protection algorithm was evaluated with PSCAD (Power Systems Computer Aided Design) simulations, and results were found to be effective for the considered fault cases. [ABSTRACT FROM AUTHOR]

Increasing numbers of photovoltaic systems and heat pumps in existing building clusters can lead to an overload of the associated electric grid substations. Based on a multi-agent-based simulation of three building cluster types the impact of building flexibility in regard to the residual substation load is studied. Each building announces its available flexibility, e.g., "heat pump can be switched off/on". A cluster master coordinator evaluates the incoming offers and decides which offers are accepted in regard to the substation's capacity utilization. The goal is to honour the substation's limit by shifting the residual load. This paper presents results from three typical urban building clusters for different penetration scenarios in regard to heat pumps, photovoltaic systems, batteries and electric vehicles. It is shown that in the studied building clusters a high penetration of heat pumps and photovoltaic systems can violate the existing substation's limits, regardless of the efforts by the master coordinator. Batteries of typical capacities cannot reduce the peak residual load. The load shifting options of the master coordinator are limited. [ABSTRACT FROM AUTHOR]

Due to its ability to deal with non-determinism and partial observability, represent goals as an immediate reward function and find optimal solutions, planning under uncertainty using factored Markov Decision Processes (FMDPs) has increased its importance and usage in power plants and power systems. In this paper, three different applications using this approach are described: (i) optimal dam management in hydroelectric power plants, (ii) inspection and surveillance in electric substations, and (iii) optimization of steam generation in a combined cycle power plant. For each case, the technique has demonstrated to find optimal action policies in uncertain settings, present good response and compilation times, deal with stochastic variables and be a good alternative to traditional control systems. The main contributions of this work are as follows, a methodology to approximate a decision model using machine learning techniques, and examples of how to specify and solve problems in the electric power domain in terms of a FMDP. [ABSTRACT FROM AUTHOR]

Process bus communication has an important role to digitalize substations. The IEC 61850-9-2 standard specifies the requirements to transmit digital data over Ethernet networks. The paper analyses the impact of IEC 61850-9-2LE on physical protections with (analog-digital) input data of voltage and current. With the increased interaction between physical devices and communication components, the test proposes a communication analysis for a substation with the conventional method (analog input) and digital method based on the IEC 61850 standard. The use of IEC 61850 as the basis for smart grids includes the use of merging units (MUs) and deployment of relays based on microprocessors. The paper analyses the merging unit's functions for relays using IEC 61850-9-2LE. The proposed method defines the sampled measured values source and analysis of the traffic. By using neural net pattern recognition that solves the pattern recognition problem, a relation between the inputs (number of samples/ms—interval time between the packets) and the source of the data is found. The benefit of this approach is to reduce the time to test the merging unit by getting the feedback from the merging unit and using the neural network to get the data structure of the publisher IED. Tests examine the GOOSE message and performance using the IEC standard based on a network traffic perspective. [ABSTRACT FROM AUTHOR]

Distributed energy resources (DERs) are being widely interconnected to electrical power grids. The dispersed and intermittent generational mixes bring technical and economic challenges to the power systems in terms of stability, reliability, and interoperability. In practice, most of the communication technologies in DER are provided by proprietary communication protocols, which are not designed for the prevention of cyber security over a wide area network, and methodology of DER integration is not unified. This has made it technically difficult for power utilities and aggregators to monitor and control the DER systems after they are interconnected with the electrical grids. Moreover, peer to peer communication between DER systems as well as local intelligent computation is required to reduce decision latency and enhance the stability of the smart grid or microgrid. In this paper, the first, novel architecture of IEC 61850 XMPP (extensible messaging and presence protocol) of the edge computing gateway, involving advanced concepts and technologies, was developed and completely studied to counter the abovementioned challenges. The results show that the proposed architecture can enhance the DER system's effective integration, security in data communication and transparency for interoperability. The novel and advanced concepts involve first modeling the topology of the photovoltaic (PV) station to IEC 61850 information models according to the IEC 61850-7-4 logical nodes and the DER-specific logical nodes defined in IEC 61850-7-420. This guarantees the interoperability between DER and DER, DER and utility and DER and the energy service operator. The second step was to map the information models to IEC 61850-8-2 XMPP for the specific communication protocol in DER applications. XMPP protocol, a publish/subscribe communication mechanism, is recommended in DER applications because of its characteristics of cybersecurity and authenticated encryption. After that we enabled the edge computing capability for data processing and the analytics of the DER side for time-critical missions. The aggregated data was then sent to the control center in the cloud. By applying the edge computing architecture, the system reduced decision latency, improved data privacy and enhanced security. The goal of this paper was to introduce the practical methodologies of these novel concepts to academics and industrial engineers. [ABSTRACT FROM AUTHOR]

In recent years, because of increasing frequency and magnitude of extreme weather events, the main stakeholders of electric power systems are emphasizing issues about resilience. Whenever networks are designed and development plans are drawn, this new feature must be assessed and implemented. In this paper, a procedure to evaluate the resilience of a distribution network against flooding threats is presented. Starting from a detailed analysis about the resilience of each asset of the grid, the procedure implements the exploration of the network in order to evaluate the impact of interruptions (e.g., in terms of number of disconnected users) produced by the specific threat; then, it calculates the resilience indices of the whole system. The procedure is applied with respect to the flooding threats, on a real distribution network in the center of Italy (i.e., the distribution network of Terni). Referring to this case study, the proposed method suggests countermeasures able to reduce the impact of flooding events and evaluates their benefits. Results indicate that, at the present time, the network is adequately resilient with respect to flooding events, as demonstrated by the index values. However, the remedial actions identified by the procedure are also able to improve the resilience of the network and, in addition, they are in agreement with the development plan already established by the distribution system operator (DSO). [ABSTRACT FROM AUTHOR]

Reasonable distribution network planning schemes can not only improve the power quality and power supply capacity of the power system, but also increase the economic benefits and welfare of the whole society. In this work, a bi-level optimization model is proposed for the joint planning of substations and lines in looped urban distribution systems. The upper-level model aims to address the substation locating and sizing problem, whereas the lower-level model the network planning problem. Both the substations directly supplying power to a load and the contralateral substations that act as backup power source to the load are considered in the bi-level model. In order to solve the bi-level planning model which is mathematically mixed integer programing and with plenty of continuous and discrete variables, the bird swarm algorithm is improved and applied based on the idea of parallel computing of big data theory. Simulations on actual planning problems are employed to verify the effectiveness of the proposed bi-level distribution network planning model and the parallel bird swarm algorithm. [ABSTRACT FROM AUTHOR]

As a result of the high efficiency of ice-melting and the small power supply capacity, DC ice-melting devices are widely used in relation to transmission lines in the power grid. However, it needs to consume reactive power when ice-melting, and voltage fluctuation of the substation may be caused when the demand for reactive power is large. It also generates a large number of 5th and 7th harmonics when ice-melting. In this paper, combined with the demand for ice-melting for transmission lines and the dynamic reactive power of substations, a low-harmonic DC ice-melting device capable of simultaneous reactive power compensation is studied. The function of ice-melting and reactive power compensation can be operated simultaneously and the rectifier's main harmonics can be eliminated. The simulation and experimental research on the device was carried out in the 500 kV Chuanshan substation. The actual ice melting was carried out on the 500 kV Chuansu I line and took only 68 min to melt the ice. The 500 kV bus voltage had no negative deviation, and the positive deviation decreased from +3.09% to +1.57% within 24 h of testing. The results prove the feasibility of the proposed DC ice-melting device in this paper. [ABSTRACT FROM AUTHOR]

With the increasing interaction between physical devices and communication components, the substation based on the IEC 61850 standard is a type of cyber–physical system. This paper proposes a reliability analysis method for substations with a cyber–physical interface matrix (CPIM). This method calculates the influences from both the physical device failures and the communication devices failures. Two indices, Probability of Load Curtailments and Expected Demand Not Supplied, are used in the reliability analysis. Given the simplified model of the practical substation based on the Chinese IEC 61850 standard, the results show that the substation system had a potential risk of cascading failure under the cyber–physical fusion trend, as the failure in cyber layer would increase the power loss of the whole system. The changing magnitude of Expected Demand Not Supplied increased significantly with increasing transmission delay rate of the process bus. [ABSTRACT FROM AUTHOR]

Regional protection based on multisource information of a regional power network depends on communication technology. A partition strategy considering communication constraints and implementation techniques must be considered to realize the regional protection of a large power grid. This paper aims at examining the technical requirements of rapid and reliable regional protection, considering the number of hops as the factor affecting communication between secondary substations and primary substations, and combining this with the equalization of substations. Then, a primary substation selection model of regional protection based on an exhaustive method is proposed using the Floyd–Warshall algorithm (an algorithm for finding shortest paths in a weighted graph). The partition model is further established according to the multifactors that affect the communication delay time for regional protection. Focusing on the N-1 channel fault in the preset region after the formation of the subregions, this paper analyzes the circuitous process of information in an interrupt channel and considers the influence of communication delay time to further improve the partition strategy. Finally, this paper puts forward techniques for partition strategy implementation based on graph theory; an example analysis of an actual power network is also given, and the conclusions of multiple partitions of the same power network are compared and analyzed. Besides this, partition suggestions and theoretical guidance considering actual engineering demands are given. [ABSTRACT FROM AUTHOR]

This paper investigates the possible options for achieving a substantial reduction in a substation footprint using air-insulated switchgear as a more environmentally-friendly alternative to gas-insulated substations that use SF6 gas. Adopting a new approach to surge arrester location and numbers, International Electrotechnical Commission (IEC) minimum clearances can be successfully selected instead of the maximum clearances as currently adopted by many utilities, as is the case in the UK. In addition, innovative alternative compact busbar arrangements using vertical and delta configurations have been proposed by the authors. A further opportunity for compaction is offered by the application of compact and integrated technology offered from several manufacturers. The full overvoltage control within the entire substation under any surge condition is a key aspect of the feasibility of this type of substation. This work demonstrates that the new design option can be an attractive alternative for future substation configuration with minimum footprint. [ABSTRACT FROM AUTHOR]

Visions of energy transition focus on activating end users, meaning that numerous flexible-distribution network-level devices become active participants in power-system operations. This implies a fast, reliable, and secure exchange of data, enabling the distribution-system operators to maintain, or even improve, the quality and delivery of service. With the introduction of the International Electrotechnical Commission (IEC) 61850 standard, the path is set for a single communication topology covering all substation levels. The standard has the potential to change the way substations are designed, built, tested, and maintained. This means that the key segment of the substation, its protection system, will go through a transition period with the end goal of having a digitized substation where all information exchange is performed over an Ethernet communication bus. This paper analyzes the performance impact of the IEC 61850-9-2LE on the protection system. To do this, a laboratory hardware-in-the-loop test setup was developed representing traditional-, hybrid-, and digital-substation topology. The setup serves to simulate faults and create transient waveforms in an extended IEEE 123-node test system, which is then used to detect the reaction times of protection relay devices. To verify the results, a significant number of tests was performed clearly showing the benefits of digitalizing the distribution system. [ABSTRACT FROM AUTHOR]

The grounding grid is a key part of substation protection, which provides safety to personnel and equipment under normal as well as fault conditions. Currently, the topology of a grounding grid is determined by assuming that its orientation is parallel to the plane of earth. However, in practical scenarios, the assumed orientation may not coincide with the actual orientation of the grounding grid. Hence, currently employed methods for topology detection fails to produce the desired results. Therefore, accurate detection of grounding grid orientation is mandatory for measuring its topology accurately. In this paper, we propose a derivative method for orientation detection of grounding grid in high voltage substations. The proposed method is applicable to both equally and unequally spaced grounding grids. Furthermore, our method can also determine the orientation of grounding grid in the challenging case when a diagonal branch is present in the mesh. The proposed method is based on the fact that the distribution of magnetic flux density is perpendicular to the surface of the earth when a current is injected into the grid through a vertical conductor. Taking the third order derivative of the magnetic flux density, the main peak coinciding with the position of underground conductor is accurately obtained. Thus, the main peak describes the orientation of buried conductor of grounding grid. Simulations are performed using Comsol Multiphysics 5.0 to demonstrate the accuracy of the proposed method. Our results demonstrate that the proposed method calculate the orientation of grounding grid with high accuracy. We also investigate the effect of varying critical parameters of our method. [ABSTRACT FROM AUTHOR]