Special Protection Systems Research Articles

Big data algorithm for computer network information security in the 5G era

Computers play a very important role in today’s life. A large amount of personal information exists in computers, so it is very important to protect the information security on computer networks. The development of information technology has brought a huge impact on human society, and the information security of its computer network has attracted more and more attention. Aiming at the needs of computer network information management in the age of big data, this paper has developed a special computer network information protection system to deal with various threats and constantly improve the protection system. Based on this, the concept and advantages of the 5G network are first expounded, and the management technology of the 5G network is briefly analyzed. Then the information security problems of computer networks in the 5G era are considered, and effective solutions to the information security problems are proposed. Through research and calculation, the new computer network security system can improve network information security by 13.4%.

Comprehensive Analysis of Transient Overvoltage Phenomena for Metal-Oxide Varistor Surge Arrester in LCC-HVDC Transmission System with Special Protection Scheme

This paper proposes a systematic and deterministic method for metal-oxide varistor (MOV) surge arrester selection based on the comprehensive analysis in line-commutated converter (LCC)-based high-voltage direct current (HVDC) transmission systems. For the MOV surge arrester, this paper investigates several significant impacts on the transient overvoltage (TOV) phenomena, which is affected by practical factors such as an operating point of the LCC-HVDC system, synchronous machine operating status of the power system, AC passive filter trip, and communication delay in a special protection system (SPS). In order to determine an appropriate rating of surge arrester, especially for TOV, this paper considers a pattern, magnitude, and duration of TOV based on various fault scenarios in an electrical power system with an LCC-HVDC system. A screening study method with 60 Hz and RMS-based balance system is conducted for examining a wide range of fault scenarios, and then for the specific test cases that need a detailed analysis, electro-magnetic transient (EMT)-based analysis models are developed with an approvable boundary setting method through the equivalent network translation tool. A detailed EMT study is subsequent based on the distinguished cases; as a result, the exact number of metal-oxide resistor stacks could be obtained through the detailed TOV study according to this procedure. The efficacy of the selection method from the proposed procedure based on the comprehensive analysis are verified on a specific power system with a 1.5 GW DC ± 500 kV symmetric monopole LCC-HVDC transmission system.

A Novel Fast Transient Stability Assessment of Power Systems Using Fault-On Trajectory

In this article, for fast transient stability status (TSS) prediction, a new scheme is proposed, which does not require any postfault data and predicts TSS using data measured until the end of the fault-on period. In this method, phasor measurement units (PMUs) are located at synchronous generators' (SGs) buses to gather time-synchronized data. Then, these measurements are applied to the proposed procedure to calculate the feature set utilizing fault-on and prefault information and predict TSS by a decision tree classifier. Since the feature set does not include any postfault (i.e., after short-circuit clearance) data, the proposed method has the capability of fast prediction of postdisturbance TSS, and hence, it provides more opportunity for system operators and/or special protection systems to implement timely corrective actions to prevent instability. Also, the results of the time-domain analysis carried out in IEEE14-bus, IEEE39-bus, 16-Machine (68-bus), and IEEE118-bus test systems and comparison of them with previous techniques reveal that although the proposed method requires fewer PMUs, it can forecast TSS accurately under N-1 and N-2 conditions. Besides, these results confirm that, considering the measurement error, when the rotor angle of SGs is estimated using the data measured by WAMS, the proposed method accurately predicts TSS.

Cascading verification initiated by switching attacks through compromised digital relays

Attackers are able to enumerate all devices and computers within a compromised substation network. Digital relays deployed in the substation are the devices with IP addresses that can be discovered in the process of trial-and-error search. This paper is concerned with studies of cyberattacks manipulating digital relays to disruptively disconnect the associated breakers. The plausible enumeration of such disruptive attack for each relay in a substation is verified with the dynamic simulation studies with the special protection system for frequency, voltage, and rotor angle stability. A pertinent approach with smaller scale contingency analysis results is proposed to reduce the enormous computation burden. The devised enumeration reduction method is evaluated using IEEE test cases. The proposed method provides an extensive enumeration strategy that can be used by utility engineers to identify the pivotal relays in the system and can be further strengthened with security protection.

Transient Stability Control Based on Kinetic Energy Changes Measured by Synchronized Angular Velocity

Real-time transient stability studies are based on voltage angle measures obtained with phasor measurement units (PMUs). A more precise calculation to address transient stability is obtained when using the rotor angles. However, these values are commonly estimated, which leads to possible errors. In this work, the kinetic energy changes in electric machines are used as a criterion for evaluating and correcting transient stability, and to determine the precise time of insertion of a special protection system (SPS). Data from the PMU of the wide-area measurement system (WAMS) are used to construct the SPS. Furthermore, it is assumed that a microcontroller can be located in each generation unit to obtain the synchronized angular velocity. Based on these measurements, the kinetic energy of the system and the respective control action are performed at the appropriate time. The results show that the proposed SPS effectively corrects the oscillations fast enough during the transient stability event. In addition, the proposed method has the advantage that it does not depend on commonly proposed methods, such as system models, the identification of coherent machine groups, or the structure of the network. Moreover, the synchronized angular velocity signal is used, which is not commonly measured in power systems. Validation of the method is carried out in the New England power system, and the findings show that the method is helpful for real-time operation on large power systems.

Development and Validation of a Special Protection System for Internal Fault in a High-Power Three-Level NPC VSC

This paper describes the development and validation of an innovative protection system based on medium-voltage fuses for a high-power switching conversion system. This special conversion system, rated to deliver about 56 MW to the load, is based on neutral-point clamped IGCT inverters, connected to the same dc link through a set of distributed busbars, with a dc-link voltage of 6.5 kV and a capacitive stored energy up to 837 kJ. The sudden release of this energy in case of a switch failure in one inverter and the subsequent short circuit of one leg can lead to destructive consequences. From the analysis of different protection strategies, performed by numerical simulations of the fault evolutions, the developed solution based on medium-voltage fuses was found the only provision able to cope with such high stored energy and uncommon circuit topology. Custom fuses were developed for this application, and a specially tailored test was designed for validating the fuse selection. The paper, after summarizing the work carried out to simulate the fault evolution and select the protection, presents the analyses carried out to set up the validation test, and describes and discusses the results of the test and the complementing numerical simulations, which demonstrated the effectiveness of the protection system.

A remote test method for power grid security and stability control system and its engineering application

Security and stability control (SSC) system or special protection system (SPS) is an important means to ensure the safe operation of power grid. In view of the insufficiency that the current open-loop testing method cannot fully test the SSC system on-site, a remote real-time closed-loop test method is proposed. The solutions of key techniques such as information interaction, remote communication and signal conversion in remote test system are studied. Then the platform architecture and standard interface of the remote test system are designed. A remote test platform for SSC system is developed, and there application modes of the platform is deeply analysed. Finally, taking SSC system of Yunnan AC power outgoing grid as pilot application, experiment of two substations on-site is carried out. The results in practical project further prove the effectiveness of the method presented in this paper.

Containment of coronavirus by the Hungarian Prison Service

The Hungarian Prison Service has developed in a fast response to the situation a special protection system for health and safety of the captives and the staff. The measurements released during the pandemic attendance served and ensured in a complex way that in Hungary no captives with coronavirus disease has been found until now. The positive value judgement of professional decision makers and of the society have proofed for commanders and staff the results of a legal and professional fulfilment of tasks. One of the most important lessons in containment of the coronavirus pandemic is that the most effective way of protection can be, until the appearance of a proofed effective vaccine, responsible attitude and connecting to that the compliance with preventive measurements.

A Remedial Action Scheme to Prevent Mid/Long-Term Voltage Instabilities

The main objective of this article is to propose a special protection system (SPS) to execute efficient remedial actions to prevent mid-term and long-term voltage instabilities. In this method, when the operating point (OP) leaves the normal operation state, the proposed SPS is initiated to execute the required corrective remedial actions to bring the OP back to a normal state and maintain bus voltages above prespecified thresholds. Considering the local nature of Volt/Var control and in order to execute fast remedial actions, in this approach, the required generation rescheduling or load shedding procedures were selected based on the electrical distance concept. This allows for remedial actions with the highest impact on volt/var control. In addition, in generation rescheduling procedures, the proposed method uses the ability of utility-scale photovoltaic resources, which can change their generation quickly. This plays a major role in maintaining stability of power systems. Efficiency of the proposed algorithm was validated through several scenarios performed in IEEE 39-bus, Nordic32, and PST 16 test systems using DIgSILENT PowerFactory software. Results of these dynamic simulations and their comparison with some previously published methods show the effectiveness of this method in timely executing appropriate remedial actions to maintain system stability.

Voltage stability analysis of the Nigerian Power System using annealing optimization technique

The paper addresses the means of overcoming the challenge posed by voltage collapse to the stability of the Nigerian electric power system. The technique applied is based on time identification algorithm elaborating, at a given grid bus, the local phasor measurements at fast sampling rate. Elements such as adjustable shunt compensation devices, generator reactive generation, transformer tap settings are optimally adjusted at each operating point to reach the objective of minimizing the voltage stability index at each individual bus as well as minimizing the global voltage stability indicator. The control elements setting were optimized and the maximum possible MVA voltage stable loading has been achieved and a best voltage profile was obtained. Results of tests conducted on a 6-bus IEEE system and a typical 28-bus Nigerian power distribution network are presented and discussed.
 Keywords: Special protection systems, voltage stability analysis, voltage stability limit, voltage collapse mechanism, system security

Experiences on Remediation of Special Protection System for Kinmen Power System in Taiwan

The isolated power system in Kinmen Island, Taiwan has already implemented the special protection system (SPS) to prevent various critical contingencies that occurred during the past decade. However, when a severe N-2 contingency occurred on July 26, 2013, the SPS has not properly armed its under-frequency load shedding. After reexamining transient recorded waveforms, it was observed that the system still has sufficient spinning reserve and the coordination between the under-frequency relay and the current SPS was not well considered. In this article, the current SPS is further modified in order to avoid the occurrence of the excessive load shedding under similar N-2 contingencies. Extensive time-domain dynamical simulations are performed first to study the relationship between the amount of the load shedding and frequency deviations under these extreme N-2 contingencies. Based on these simulation results, the remediation scheme of the SPS will be proposed by modifying the existing SPS design logic and the amount of load shedding. More comprehensive input triggered states are proposed for identifying these severe N-2 contingencies. Both simulation verifications under the proposed remedial scheme and actual transient recorded waveforms under a severe contingency after commissioning this remediated SPS are provided to demonstrate the effectiveness of this proposed remediation scheme.

Development of Prototype MGB 2 Superconducting Solenoid Magnet for High-Efficiency Klystron Applications

A wind-and-react MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> solenoid magnet for klystrons has been developed. While the current normal-conducting (Cu) magnet consumes 20 kW per magnet, this MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> magnet consumes less than 3 kW in refrigerator power. The conduction-cooled half coil of the magnet is 337 mm in inner diameter; the winding pack, 19.4 mm wide × 136.6 mm high, uses 2.7 km of 10 filament circular conductor, which is insulated with glass 0.83 mm in diameter, and is reacted after being wound onto a stainless steel bobbin. The coil has Cu plates of 0.2 mm in thickness between each coil layer and on the inner and outer sides. The magnet has two coils and produces 0.8 T in the center and its stored energy is 11.8 kJ. Together with the above-mentioned coil structure, these coils can consume stored energy in itself at quench without a special quench protection system. A performance test of the magnet was successful.

Designing centralised and distributed system integrity protection schemes for enhanced electric grid resiliency

System integrity protection schemes (SIPSs) are installed at substations to preserve power system stability by preventing bottlenecks in transmission and distribution networks and improving the overall reliability. SIPSs are also referred to as remedial action schemes, emergency control systems, special protection systems, and wide-area control schemes. Typical SIPSs have centralised computing architectures with applications to ensure reliable power system responses during transmission outages, remediate regional transmission bottlenecks caused by delays in the construction of new lines, prevent severe instability and blackouts due to faults and inadvertent disconnections, prevent line damage resulting from thermal limits, avoid voltage collapse, and protect against other critical events in the power system. This study proposes a distributed computing architecture for SIPSs, including algorithms that use DC and AC optimal power flow. The authors classify SIPS applications based on control types and propose novel algorithms for next-generation SIPSs using synchrophasors and real-time technology. The authors also propose testing requirements and architectures for validating SIPSs prior to field installation. Lastly, the authors share results obtained using the proposed SIPS for a transmission overload condition caused by excessive wind generation.

Analysis of Computer Network Information Security and Protection Strategy

Computers are closely related to our life and work. We have entered an era in which computers are not available in all walks of life. Among them, many important documents and materials will be stored in the form of electronic files in the computer. However, computers are not absolutely safe, and cases of information theft occur from time to time. Most people usually keep information confidential in the form of encryption. How to avoid the problem of computer information security. Computer network security involves all aspects. To solve these problems, there are many levels of technology, such as cryptography technology, network security technology and so on. Our country has also done a lot of research on the security protection of computer network technology, and these research results have also achieved certain results in the actual construction of computer network. In order to ensure the normal operation of computer networks, ensure information security and prevent information leakage and theft, a special protection system has been established to ensure the security of computer network information by setting up computer detection, security assessment and other links. However, with the rapid development of science and technology, the updating of electronic products is faster and faster, and the challenge of Wechat for network security information is more severe. How to protect computer network information security needs to be solved urgently, this paper discusses this.

Novel Transient Power Control Schemes for BTB VSCs to Improve Angle Stability

This paper proposes two novel power control strategies to improve the angle stability of generators using a Back-to-Back (BTB) system-based voltage source converter (VSC). The proposed power control strategies have two communication systems: a bus angle monitoring system and a special protection system (SPS), respectively. The first power control strategy can emulate the behaviour of the ac transmission to improve the angle stability while supporting the ac voltage at the primary level of the control structure. The second power control scheme uses an SPS signal to contribute stability to the power system under severe contingencies involving the other generators. The results for the proposed control scheme were validated using the PSS/E software package with a sub-module written in the Python language, and the simple assistant power control with two communication systems is shown to improve the angle stability. In conclusion, BTB VSCs can contribute their power control strategies to ac grid in addition to offering several existing advantages, which makes them applicable for use in the commensurate protection of large ac grid.

A new mechanism for remedial action schemes design in a multi-area power system considering competitive participation of multiple electricity market players

Unlike to common protective devices that are used for protection of power system equipment, Special Protection System (SPS) means an automated protective system which detects abnormal and predetermined conditions of the power system and applies preplanned corrective actions in order to maintain system integrity. The SPS is widely used in a restructured environment because it is known as a rapid and low cost alternative for network expansion to increase the transfer capability. Although the economic motivations and technical aspects of SPS are proposed in some references, the economic design of an SPS in a restructured environment has received less attention. In this paper, an economic-based method is presented to design remedial action schemes in a Multi-Area Power System (MAPS) with presence of Multiple Electricity Markets (MEM). The innovations of the proposed method are twofold: on one hand, the protection schemes are updated after each electricity market clearing that increases its performance because of the proximity to real time conditions. On the other hand, these remedial actions are designed economically in an environment with several independent Market Operators (MOs) through the interaction with a central coordinator entity. The proposed method is applied on a three-area test system and its results are presented by further explanation of its technical and economic advantages.

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.

Earthquake Response Control of RC Water Tower Frame Staging Using Special Protection System Sakshi Manchalwar

Earthquake Response Control of RC Water Tower Frame Staging Using Special Protection System Sakshi Manchalwar

Application possibilities of special lightning protection systems of overhead distribution and transmission lines

Reduction of the overhead lines back-flashover rate (BFR) after application of special lightning protection systems is analyzed in this paper. The following lightning protection systems are considered: line arresters, underbuilt wires, additional shield wire and guy wires. Partial or combined efficiencies of mentioned lightning protection systems are analyzed. Overhead distribution (35 kV) and transmission (110 kV and 220 kV) lines BFR are estimated through the semi-statistical calculation procedure as suggested in international technical documents. System equivalent circuits in the EMTP-ATP software are created with carefully chosen models and parameters of elements. Pursuant to the estimated results, conclusions about application possibilities of different lightning protection systems are given.

Design and Deployment of Special Protection System for Kinmen Power System in Taiwan

If an extreme contingency strikes the Kinmen Island power system in Taiwan, it is very likely to cause blackouts. Although an underfrequency protection scheme has been applied, some drawbacks of the protection scheme hinder the Kinmen power system from avoiding blackouts. In the past decade, several blackouts have occurred in the Kinmen power system. To avoid further possible blackouts, a special protection system (SPS) is summoned. This paper describes the design guidelines and deployment procedures of an SPS for the Kinmen power system. The design depends on the Kinmen power system characteristics, and the deployment hinges upon the supervisory control and data acquisition system. Exquisite software was also developed to testify the Kinmen system SPS. Operational records have demonstrated that the proposed SPS can indeed prevent blackouts from occurring in the Kinmen power system. The design, implementation, and operation of the SPS dealt with in this paper might foster further deployments of other SPSs.