Special Protection Scheme Research Articles

Applying a model-driven approach to the development of power plant SCADA/EMS software

In this paper, we propose and apply a model-driven approach to develop applications that compose a suite known as Energy Management System (EMS). EMS is an essential tool for the operation of electrical systems. Although models of cyber–physical phenomena are extensively used in planning, designing, and operating power systems, the development of EMS applications often uses such models only as support and documentation, while the main artifact throughout the software development process is source code. In other words, the models are used merely to document and communicate some aspects of a system. The evolution of such a system is expensive and error-prone, requiring specialized personnel, skilled in both software engineering and power systems. Some of the problems arising from this manual process include: (i) substantial implementation effort in interpreting models and manually translating them into programs; (ii) greater risk of introducing software defects; (iii) risk of leaving documentation outdated, or implementation inconsistent with the intended design. Model-Driven Engineering (MDE) is an approach to constructing computing systems in which models are used as primary engineering artifacts, while programs (and other products) are automatically generated from the models, thus addressing the above limitations. MDE approaches have been adopted in several industrial areas, including smart grid automation, in which specialized modeling languages and tools facilitate the production of executable software from high-level models. For SCADA/EMS software development, however, a dedicated approach is still absent. We address these issues by proposing D-SPADES: a Model-Driven Engineering approach tailored to the EMS domain. D-SPADES defines a domain-specific modeling language based on block diagram notation, called EMSML, specifically targeted to describe the behavior of EMS applications. It also defines the associated mapping strategies and harnesses a set of tools for automatically transforming models into source code of applications that can be integrated into existing SCADA platforms. We have applied D-SPADES to model and automatically generate source code for two different applications from the Itaipu power plant: a voltage and reactive power controller and a component for a system-wide special protection scheme. Both applications were validated using a power system simulator and performed satisfactorily. The special protection scheme was deployed to the production system. Hence we demonstrate that D-SPADES is a viable approach to developing mission-critical applications.

The impact of war in Ukraine on EU migration

When the Russian Federation invaded Ukraine on 24 February 2022, one of the most immediate and dramatic reactions of the European Union (EU) was to open a special protection scheme for Ukrainians and non-Ukrainians who were resident in the country on the date of the invasion to enter the EU and remain with extensive rights (All EU states are part of the scheme with the exception of Denmark which because of particularities in its constitutional position in the EU opened a parallel national scheme rather than join the EU scheme). The legal basis of the scheme is a directive adopted in 2001, on Temporary Protection which had been slated for repeal but which had not yet occurred at the date of the invasion and is now on hold. Since then, according to UNHCR, 8,046,560 Ukrainians (or persons who were resident in Ukraine at the relevant date) have been recorded across Europe. In this article we examine the status and rights of TP beneficiaries in the EU and the challenges ahead for them and the EU as the war continues.

The ECCANDE Project: Design, Field Implementation, and Operation of a Special Protection Scheme Based on Synchronized Phasor Measurements

This paper presents the ECCANDE project, one of the first Special Protection Schemes (SPS) conceived to rely on the structure of a Wide-Area Monitoring, Protection, and Control System (WAMPACS) and currently operating in a real, large-sized power system. This project was developed and implemented to enable the interconnection between the Argentinean and Paraguayan bulk power transmission systems, which involves and directly affects two of the largest hydropower plants in the world (the Itaipu and Yacyreta power plants). Building this WAMPACS-based SPS took more than a decade of work performed by multiple teams, involving modeling, planning studies, design, manufacturing, real-time hardware-in-the-loop (HIL) simulation for equipment testing, implementation, commissioning, field tests and evaluation of daily operation. The paper describes how system stability problems (detected during the initial studies for the interconnection) made it clear that the ECCANDE SPS had to be a WAMPACS-based one, and how its architecture and logic functions were conceived to deal with these problems. The results of HIL real-time simulations and a main field test show that the ECCANDE SPS enabled the interconnection, successfully protecting against the loss of synchronism between the Itaipu and Yacyreta power plants before the system separation.

A novel high‐voltage solid‐state switch based on the SiC MOSFET series and its overcurrent protection

AbstractAll‐solid‐state switches are one of the core components of pulsed power supply systems. However, the voltage level of a single switch is limited. By optimizing the chip structure, the voltage level of a single switch can be improved. Due to the immaturity of the production process and the positive correlation between the blocking voltage and the on‐resistance of the switch, it is difficult to improve the blocking voltage and the continuous forward current of a single switch simultaneously. The series‐connected switch is a way to increase the switch's blocking voltage without reducing the switch's continuous forward current. Magnetically coupled isolated drive and resistor‐capacitor forced voltage equalization techniques are investigated to increase the blocking voltage of the switches using multiple SiC metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) in series connections. Meanwhile, a special overcurrent protection scheme is designed to improve the reliability of the series‐connected switch. Finally, a high‐voltage solid‐state switch is developed based on the SiC MOSFET series connections, whose output pulse width is adjustable from 20 to 300 μs, frequency is adjustable from 1 Hz to 3 kHz, the maximum output voltage can reach 57 kV (1 Hz), and the overcurrent protection time is about 1 μs.

An approach for the aggregation of power system controllers with different topologies

This paper proposes an approach to aggregate non-structured power system controllers preserving the dynamical characteristics of the original devices. The method is based on linear operations that use the frequency response of the elements, resulting in an accurate input–output description of the equivalent controller when compared to the original ones. The developed method was applied to a model of the future interconnected Paraguayan-Argentinean power system to produce a dynamic equivalent used in a real-time simulator to test the special protection scheme needed for the safe operation of the this future system. Transient and small-signal stability studies presented matching simulation results in the time domain with significantly reduced computational burden and processing time.

A special protection scheme for damping power system oscillations by controlling wind farms

This paper proposes a special protection scheme (SPS) as an additional tool for system operators to damp power oscillations and thereby improve the overall power system stability. This SPS is activated by an online power oscillation detection algorithm and utilizes a power system stabilizer (PSS) controlling a wind farm to damp power oscillations. Moreover, an adaptive time delay compensator (ATDC) compensates for the time delays in the control system. Different alternatives for the PSS input signals are compared by time-domain simulations and by small-signal analysis. The most significant improvement in the damping of the inter-area oscillations is achieved when the PSS uses the active tie-line power as input and controls the active power of the wind farm. The results also prove that the ATDC operates correctly if the total time delay remains below 300 ms. This SPS can improve the system stability when the conventional PSSs may be insufficient.

Micro-synchrophasor based special protection scheme for distribution system automation in a smart city

IntroductionAspects of power system protection which contributes to mal-operations and blackouts can be improved by supervision of system behavior and response based analysis rather than condition-based or event-based analysis using wide area measurements based on synchrophasor technology. The paper explores the application of micro-Phasor Measurement Unit for time synchronized real-time distribution network monitoring and agile decision support schemes for system prognosis and control.Case descriptionThe scheme is proposed as part of a project on “Power System Voltage Stability Analysis using synchrophasors in Distribution System of Kerala Grid” at Kerala State Electricity Board Ltd. An actual grid occurrence during the severe tropical cyclone Ockhi, is considered as the base case which motivated the work.Discussion and evaluationA voltage stability index (VSI) based special protection scheme (SPS) for radial distribution network at a proposed smart city is presented in the present study. The proposed special protection scheme on actual implementation can use data from proposed local micro-Phasor Measurement Unit. The PMU is proposed to be placed at one of the key nodes of the distribution system network in the city.ConclusionThe VSI is derived using local phasor values and is used to initiate a Special Protection Scheme for N-1 contingency at the key node, so as to ensure availability of the most essential feeder which provides supply to a hospital campus housing several health institutes of prime importance. The voltage stability index derived is tested and SPS is validated using real-time grid data.

A Detailed Presentation of an Innovative Local and Wide-Area Special Protection Scheme to Avoid Voltage Collapse: From Proof of Concept to Grid Implementation

For more than a decade, Hydro-Quebec Research Institute (IREQ) has been involved in different strategic research and development activities to maintain the stability and security of the Hydro-Quebec network. An innovative project, so-called global and local control of compensators (GLCC), was initiated for wide-area and local control of dynamic shunt compensators such as static VAR compensators and synchronous condensers to increase its transfer capacity. The objective of the GLCC project is the development of a new special protection scheme (SPS) to maintain voltage stability after events resulting in large voltage drop using local and wide-area network measurements based on telecommunications and phasor measurement units. The core of the GLCC special protection scheme is the substation control unit (SCU) which includes all the intelligence of the whole GLCC control system. This paper presents the details of the functions of the SCU controller which has been designed, developed, and intensively tested by Hydro-Quebec with a dedicated replica at IREQ power system simulation laboratory. Results of both hardware-in-the-loop real-time simulations and field tests showed the reliability, robustness and security of the SCU controller. On that basis, a deployment on Hydro-Quebec network started to implement the GLCC SPS solution at all shunt compensator substations.

Semi-Adaptive Setting of Under Frequency Load Shedding Relays Considering Credible Generation Outage Scenarios

Severe generation outages may affect the power system frequency stability and cause abnormal frequency declines especially under the high penetration of low inertia generation technologies. Under frequency load shedding (UFLS), as a special protection scheme, is utilized to restore the power balance and maintain system frequency in an acceptable range. This paper develops a semi-adaptive UFLS plan in which the multistage load shedding is triggered based on the rate of change of frequency value. The proposed semi-adaptive UFLS plan activates predetermined later stage as early stage under the severe generation deficiencies. Most credible power imbalance scenarios including conventional generation outages and islanding scenarios are considered in semi-adaptive setting of the proposed UFLS plan. In order to achieve the optimal settings, the proposed UFLS plan is formulated as a mixed integer linear programming model. The dynamic of governors and load damping are considered in the discretized system frequency response. A scoring method is developed to select the UFLS settings with the most desired system frequency response. The performance of the proposed UFLS plan is verified over the IEEE 39-bus test system under credible and most likely scenarios of generation outages.

Synchrophasor‐based system integrity protection scheme for an ultra‐mega‐power project in India

System Integrity Protection Scheme (SIPS) aids the normal protection scheme in case of certain special contingencies like tripping of important corridors/flow gates etc. to mitigate the voltage or angular instability, load generation imbalance and finally large-scale cascading catastrophes. A recent blackout incident in an ultra-mega-power project (UMPP) in India has motivated the authors to ponder upon a SIPS as a solution. As part of designing the SIPS, an efficient solution is formulated using synchrophasors for a well-known issue nonetheless an issue which still disturbs the Indian power system network with blackouts – i.e. unintended distance relay operation in the event of power swing. Here, real-time voltage and current phasors and the angular separation between the buses connecting faulted line, acquired by phasor measurement unit is utilised to derive a differential power coefficient (DPC). This study proposes a modified logic scheme for blocking/de-blocking of distance relays i.e. change the existing scheme with ‘block all zones except Zone-1’ to ‘block all zones on power swing detection’. Rate of change of DPC is derived here which aids in differentiating stable and unstable power swings. A special protection scheme is finally formulated based on the modified logic.

Special protection system to cope with the unavailability of sampling values from an entire substation

A special protection system is proposed to respond to a challenge such as that a substation must be immediately taken out of service or only be protected by a remote backup protection without selectivity if the sampling system of this substation breaks down or the samplings are unavailable even though the GOOSE channel is functioning normally. After the special protection system perceives an abnormality of the sampling system of the substation, it first locates the rough fault region using a wide area measurement system based current differential protection scheme of the sound side of the lines connected to the substation with an abnormal sampling system. Then, a novel compensation voltage difference scheme is proposed to determine the faulty line within the recognized rough fault region. Combined with the zone I distance protection scheme, a comprehensive special protection scheme to address a serious sampling abnormality is proposed. Theoretical analysis and PSCAD and MATLAB based simulation studies show that the proposed scheme has the advantages of high reliability, sensitivity and capability of withstanding a fault resistance.

Dynamic multi‐stage under frequency load shedding considering uncertainty of generation loss

Under frequency load shedding (UFLS) as a special protection scheme is executed to arrest declining frequency. The setting parameters of a multi-stage load shedding plan are determined using a discretised model of dynamic system frequency response considering uncertainty of generation loss. The proposed probabilistic UFLS plan is formulated as a mixed integer linear programming optimisation problem to minimise the expected amount of load curtailment. The uncertainty of the proposed discretised dynamic load shedding plan is modelled using the point estimate method, and the obtained results are compared with those of the Monte-Carlo simulation method (MCSM). The utilised point estimate technique converts the continuous probability distribution functions of the uncertain parameter (i.e. the generation loss) to discrete statistical moments. The proposed probabilistic UFLS is solved using the BONMIN solver. The performance of the proposed dynamic UFLS plan is investigated for the IEEE 39-bus test system.

Analysis on Special Protection Scheme of Korea Electric Power System by Fully Utilizing STATCOM in a Generation Side

Increase in power demand has required providing infrastructure, such as huge power plants and transmission lines. However, the recent trends in power system planning and operation are being toward maximum utilization of existing electricity infrastructure with tight operating margins because of new constraints placed by economic, political, and environmental issues. This might cause serious stability problems when a severe fault or a sudden outage of critical lines occurs. Therefore, the special protection scheme (SPS) has been used by generator tripping and successive load shedding to prevent a large-scale blackout by the cascading effect. If the number of tripping generators in the SPS operation is reduced, the enormous cost of power outage can be saved. This paper analyzes the enhancement of SPS via the transient stability improvement by the static synchronous compensator (STATCOM) applied to a generation side of Korea electric power system. First, its characteristic related to the SPS is described. Then, the proper capacity of STATCOM is determined with the equal area criterion to reduce the number of tripping generators. Also, the new control method for STATCOM is proposed for its full utilization. Finally, its effectiveness is verified by the case study with the practical data of Korea electric power system.

An Overview of Frequency Control as a Criterion of Power System Reliability and International Survey of Determining Operating Reserve

In this paper an extensive literature review of power system frequency control regulation and in relation to this, operating reserve determination policy have been highlighted. In terms of power system reliability and stability aspect, frequency control mechanism is the most important factor; hence there is a need for sufficient capacity reserve in case of contingency. An investigation of operating reserve policy in different regions, e.g., US, Canada, Europe and Asia have been conducted to clearer understand of reserve policy. It has been identified that, probabilistic approach is the best suited for determining generation adequacy in terms of economic and reliability point of view. Different type of reserve is allocated at different level of frequency control level. So, technical specification and timing for frequency control level of different system operator have been discussed widely. A comparison of frequency control framework between European and US is also presented. To ensure reliability and stability, it is recommended to adopt special protection scheme alongside new technologies – WAMS, SmartGrid.

Special Protection Schemes: A Survey and Vision for the Future

Any power system network is subjected to disturbances at any time and place. It is considered as one of the most stochastic system ever seen by the human beings. To enhance the power system reliability, System Protection Scheme (SPS) is an effective tool for utilizing the power grid during rare contingencies. This method is often employed as secondary protection schemes. SPS is also termed as Special Protection Scheme. SPS is referred with different names by different users such as IEEE as System Integrity Protection Scheme (SIPS), Bonneville Power Administration (BPA) as Remedial Action Scheme (RAS) and WECC and others as SPS. In India, only in late 90s, the concept of SPS was introduced to solve the above problem. In Indian power grid different SPS has been designed and implemented successfully. This paper presents a complete knowledge, need , general structure, characteristics and a brief description of the major SPS employed in various Indian Power grids. Post - commissioning performance of these SPS has also been analyzed briefly. Finally, highlights of major issues involved with the employment of SPS in the Indian scenario.

Role of Statistical and Machine Learning Methods in Special Protection Scheme Logic Design and Failure Assessment

With tremendous growth in variable renewable generation and uncertainties in power system operations, there has been lot of installations of special protection schemes in many parts of the world. A special protection scheme, also termed a remedial action scheme, is the high-end last line of defense mechanism to relieve the system from catastrophic consequences under highly stressed conditions. This article delineates the special protection scheme logic design process and, with the help of a Nordic grid case study, proposes a new paradigm of special protection scheme failure assessment and logic design process, namely the “system-view” framework. In this context, the article also demonstrates the application of decision tree-based methods to derive special protection scheme operational logic and provides a pathway to use efficient statistical sampling techniques for implementing the system-view special protection scheme failure assessment method, thereby advancing the logic redesign process.

A combined approach of methods for determining the regional assessment of the disjunct plant Primula pedemontana in Spain

The aim of this study was to conduct a regional threat-status assessment for Primula pedemontana Thomas ex Gaudin in Spain. This is an Alpine plant with a single isolated Iberian population. A major field survey was made to monitor the species in Spain with a view to preventing its possible disappearance. For that purpose, a habitat study was carried out, regional population size and population structure were determined, and major threats and conservation actions were identified. Besides, habitat suitability maps were drawn up for the present and for 2025 and the percentage of potential habitat loss was calculated in order to estimate their possible evolution. The number of mature individuals, calculated as a trapezoidal fuzzy number, was [9179; 10820; 19002; 22342]. Extent of occurrence and area of occupancy calculated were 2.5 and 0.16 km2, respectively. The regional IUCN category obtained for P. pedemontana was “Critically Endangered”. The percentage of potential habitat loss was estimated at 10.9% for 2025. The authors consider that this species is among the priority Spanish plants for conservation, and that it should be included in the “Spanish List of Wild Species under the Special Protection Scheme”.

Special protection scheme against voltage collapse

The safe and continuous operation of power systems necessitates the implementation of special protection schemes (SPSs) against severe disturbances that may lead to a system breakdown. This study proposes a new SPS to mitigate voltage collapse against predetermined contingencies that can significantly lessen the voltage stability margin (VSM) of the system. The proposed SPS is based on an effective load shedding scheme that uses a multi-objective optimisation framework including the objectives of load cut, VSM and the integral of the deviation from nominal voltage. Moreover, a new diversely distributed multi-objective fuzzy-based theta gravitational search algorithm is proposed to solve the optimisation problem. Khorasan area of Iran's power system in 2014 peak load time is used as a test case for the suggested SPS. Effectiveness of the proposed approach is shown by comparing its simulation results with the results of the current SPS and other solution approaches.

Special Protection Scheme at BTPS Power Station

After 2003 free licensees’ act in power sector, it is observed that many power plants from public sector as well as from private sectors are going to be commissioned. The load growth in India is about more than 10% pa. As these plants are going to connect to the power grid, therefore the grid is going to become more complicated. Also the problems related to grid stability are enhanced. There shall be possibilities regarding failure of grid system and under such circumstance it is always desirable to island minimum single generating unit in power plant of specified geographical area. After islanding the generating unit, this unit has to survive not only for the restoration of grid but also for power supply to important consumers. For the grid stability and effective survival of islanded generating unit, it is mandatory to maintain the power balance equation. This paper focuses on the lacunae’s observed in implementation of special protection scheme to carry out islanding operation at Bhusawal Thermal Power Station (BTPS) by considering the case studies. The concepts of islanding, load shedding, generator tripping and along with importance of power balance equation is discussed. Efforts are made to provide the solution for the survival of islanding scheme.

Biomechanical comparison of pedicle screws versus spinous process screws in C2 vertebra: A cadaveric study.

Background:Biomechanical studies have shown C2 pedicle screw to be the most robust in insertional torque and pullout strength. However, C2 pedicle screw placement is still technically challenging. Smaller C2 pedicles or medial localization of the vertebral artery may preclude safe C2 pedicle screw placement in some patients. The purpose of this study was to compare the pullout strength of spinous process screws with pedicle screws in the C2.Materials and Methods:Eight fresh human cadaveric cervical spine specimens (C2) were harvested and subsequently frozen to −20°C. After being thawed to room temperature, each specimen was debrided of remaining soft tissue and labeled. A customs jig as used to clamp each specimen for screw insertion firmly. Screws were inserted into the vertebral body pairs on each side using one of two methods. The pedicle screws were inserted in usual manner as in previous biomechanical studies. The starting point for spinous process screw insertion was located at the junction of the lamina and the spinous process and the direction of the screw was about 0° caudally in the sagittal plane and about 0° medially in the axial plane. Each vertebrae was held in a customs jig, which was attached to material testing machine (Material Testing System Inc., Changchun, China). A coupling device that fit around the head of the screw was used to pull out each screw at a loading rate of 2 mm/min. The uniaxial load to failure was recorded in Newton'st dependent test (for paired samples) was used to test for significance.Results:The mean load to failure was 387 N for the special protection scheme and 465 N for the protection scheme without significant difference (t = −0.862, P = 0.403). In all but three instances (38%), the spinous process pullout values exceeded the values for the pedicle screws. The working distances for the spinous process screws was little shorter than pedicle screws in each C2 specimen.Conclusion:Spinous process screws provide comparable pullout strength to pedicle screws of the C2. Spinous process screws may provide an alternative to pedicle screws fixation, especially with unusual anatomy or stripped screws.