Backup Protection Research Articles

A guide to protection schemes of synchronous generator-based electric grids

Ensuring the reliability of power systems remains a paramount concern for electrical utilities worldwide. The design and implementation of robust protection is crucial for mitigating faults and ensuring uninterrupted power supply. This paper encompasses the protection deployed in electrical utilities. A comprehensive analysis is conducted on the application protection scheme in practice for the protection of major power components. The reliability of protection schemes is enhanced by adopting the of dual & fast protection schemes on the critical power components for swift & reliable clearing of faults. Additionally, this article also investigates the protection strategies employed for slightly lower priority components, including high-speed main and low-speed backup protection schemes. A thorough review for the protection practices for synchronous power generation, transmission, and distribution has been conducted. In this article, the selection of specific protection schemes and the calculation settings for 600 MW synchronous generator-connected lines and transformers are discussed. Additionally, the limitations of traditional protection schemes in safeguarding inverter-based power systems are explored. The paper also highlights areas for future research in the protection of electrical equipment within evolving grid infrastructures. This study will provide valuable insights for researchers and practicing engineers in planning and implementing protection systems for electrical grids, ensuring high levels of reliability and resilience

Analysis, design, and testing of mechanical switch for the backup protection of switching network unit in fusion device

Switching network unit (SNU) is one of the important systems in the power supply system of fusion devices, which excites and establishes plasma current. A mechanical switch has been designed for SNU backup protection, which can short-circuit other components in case of SNU failure to prevent further deterioration of the situation. An optimized contact system is used in this switch to improve the maintainability of the contacts. A detailed structural design was carried out for the switch, and the final prototype test results verified that it meets the relevant design requirements. This backup protection scheme can provide a certain reference for the engineering design and reliable operation of SNU.

Synthesis of Self-Checking Circuits for Train Route Traffic Control at Intermediate Stations with Control of Calculations Based on Weight-Based Sum Codes

When synthesizing systems for railway interlocking, it is recommended to use automated models to implement the logic of railway automation and remote control units. Finite-state machines (FSMs) can be implemented on any hardware component. When using relay technology, the functional safety of electrical interlocking is achieved by using uncontrolled (safety) relays with a high coefficient of asymmetry of failures in types 1 → 0 and 0 → 1. When using programmable components, the use of backup and diverse protection methods is required. This paper presents a flexible approach to synthesizing FSMs for railway automation and remote control units that offer both individual and route-based control. Unlike existing solutions, this proposal considers the pre-failure states of railway automation and remote control units during the finite-state machine synthesis stage. This enables the implementation of self-checking and self-diagnostic modules to manage automation units. By increasing the number of states for individual devices and considering the states of interconnected objects, the transition graphs can be expanded. This expansion allows for the synthesis of the transition graph of the control subsystem and other systems. The authors used a field-programmable gate array (FPGA) to implement a finite-state machine. In this case, the proposal is to encode the states of a finite-state machine using weight-based sum codes in the residue class ring based on a given modulus. The best coverage of errors occurring at the outputs of the logic converter in the structure of the FSM can be ensured by selecting the weighting coefficients and the value of the module. This paper presents an example of synthesizing an FPGA-based FSM using state encoding through modular weight-based sum codes. The operation of the synthesized device was modeled. It was found to operate according to the same algorithm as the real devices. When synthesizing self-checking and self-controlled train control devices, it is recommended to consider the solutions proposed in this paper.

Backup protection method for half-wavelength transmission lines based on inverse-time characteristic

The advantages of ultra-high voltage (UHV) Half-wavelength AC transmission (HWACT) technology are achieving full-line reactive power self-balancing without the need for reactive power compensation equipment along the line and avoiding the Ferranti effect. Recently, this technology has gained considerable attention worldwide. While numerous main protection methods that were tailored to the unique operational characteristics of HWACT lines have been proposed, backup protection for HWACT has been overlooked relatively. As a transmission line requires both main and backup protection for safe and reliable operation, this paper analyzes the necessity of backup protection for HWACT lines and proposes a method based on inverse-time backup protection. This method relies on the rate of change of current (RCC), determines faults by calculating the initial value of the change rate of the fault current, and applies inverse-time characteristics to remove faults. This protection method demonstrates good quick-acting properties by adopting the RCC in the initial phase of a single-end fault without the need for dual-end communication. A large number of simulation results validated that this method was smaller affected by fault distance, initial fault phase angle, transition resistance and fault type, making it an effective protection approach for main protection failures.

A wide area backup protection algorithm based on fault current comparison and evidence theory fusion

Abstract Wide-area backup protection using information in the area to determine the fault location comprehensively requires a high fault tolerance ability. However, the traditional wide area backup protection algorithm based on evidence theory assigns a separate value to each adjacent line for its fault probability, and the performance of the algorithm degrades in the condition of more information loss or errors. To solve these problems, this paper proposed a wide area backup protection algorithm based on fault current comparison and improved evidence theory fusion. The proposed method first selects the suspected fault lines by sequence voltage sorting. Then, the information on the fault current sequence component and traditional protection action is collected and preprocessed to form the evidence set, and its basic probability assignment is calculated. Finally, the improved evidence theory is used for fusion to identify fault lines. Simulation results show that the algorithm can accurately identify fault lines under complex operating conditions, multiple information loss and errors, and has high fault tolerance.

A new fault detection and relay coordination technique for low voltage DC microgrid

Integration of various distributed generation units in the DC distribution network creates an outsized impact on magnitude and direction of fault current. The specific behaviour of fault current during a short circuit fault demands quick and reliable detection and isolation of fault, which poses a significant challenge in developing an effective protection and coordination scheme for DC microgrids. In this regard, a new fault detection and relay coordination algorithm is proposed for a Low voltage DC (LVDC) microgrid, which utilizes inverse time relay characteristics based on variance of fault current. While the relay responds and picks up during both internal and external faults, its operation is automatically limited upon operation of the downstream circuit breaker without the need for any communication channel. The efficacy of the proposed strategy is evaluated by modelling a mesh-connected DC microgrid network using PSCAD/EMTDC software. The protection coordination problem is developed as a constraint non-linear optimization problem to determine optimal relay settings. The proposed approach has been tested by simulating various types of faults at different fault locations and fault resistances along with various microgrid operating modes. The results suggest that the proposed strategy stands out by optimizing relay operating time and providing backup protection while upholding relay coordination. A comparative assessment of the proposed technique with existing ones proves its effectiveness in terms of swift relay tripping time, better immunity against noise, and independency against microgrid operating mode and topology.

The adaptability research and evaluation of digital distance protection based on Python and PSCAD

With the development of power systems, digital distance protection, as an innovative and cutting-edge technology, plays a crucial role in ensuring the stable operation of the power grid. Due to its high precision, rapidity, and reliability, digital distance protection has become a key component of power system safety. Distance protection is widely used in distribution networks at or below 35 kV. Therefore, studying its adaptability and effectiveness as a remote backup protection can provide an effective foundation for improving grid security.With the utilization of Python and PSCAD, the adaptability of digital distance protection is meticulously examined in the context of low voltage side faults in 110 kV/35 kV transformers, specifically as a remote backup protection measure. The core objective of this investigation is to assess the efficacy of this protection strategy in upholding the safety and reliability of power systems. To achieve this, 3 approaches is employed: theoretical analysis, simulation modeling, and experimental validation. This process allows for a comprehensive evaluation of the performance characteristics and application efficacy of digital distance protection. The insights garnered from this meticulous study offer profound understanding into the strengths and potential limitations of this protection paradigm, serving as a solid foundation for the refinement of existing protection strategies and the enhancement of the overall resilience of power systems. In essence, this article aims to evaluate the effectiveness of digital distance protection as a remote backup protection strategy for faults on the low-voltage side of 110 kV/35 kV transformers. The core objective is to assess the efficacy of this protection strategy in maintaining the safety and reliability of the power system.

Towards resources optimization in deploying service function chains with shared protection

Emerging artificial intelligence techniques enable the Internet-connected devices automatically generate massive SFC requests in scenarios with ultra-reliability demands such as unmanned vehicle systems, smart factories. In such scenarios, it is imperative to deploy these huge amounts of SFCs in a fault-tolerant manner. The existing works on fault-tolerant SFC deployment employs the dedicated SFC backup protection with the resources redundancy of at least 100%, which addresses the ratio between the backup and primary resource consumptions. Due to this, the dedicated SFC protection likely prevents these reliable SFCs from being massively deployed. To tackle this challenge, for the first time, this work studies how to enhance the resource utilization by deploying SFCs with shared protection. First, we introduce new concepts of SFC protection set and sharing-risk SFC graph (SCG). Next, we define a new problem called SFCs embedding with SCG-based shared protection. Then, we propose a heuristic algorithm called SCG-based SFC embedding and protecting (SCG-SEP), which is proved to be logarithm-approximate. Extensive simulations show that SCG-SEP outperforms the benchmarks by an average of 12.25% and 43.67%.

Protection Coordination Strategy for the Distributed Electric Aircraft Propulsion Systems

The current trend in distributed electric aircraft propulsion systems is to utilize the DC bus system at higher voltage levels than conventional aircraft systems. With Boeing and Airbus utilizing the +/−270 V bipolar DC bus system, the research on high-voltage systems is increasing gradually, with voltage levels ranging from 1 to 10 kV systems or +/−0.5 to +/−5 kV DC bus systems. These voltage levels present considerable challenges to the distributed electric aircraft propulsion systems. In addition to partial discharge effects, there are other challenges, particularly the challenge associated with effectively limiting short-circuit fault currents due to the low cable impedance of the distribution system. The cable impedance is a significant factor that determines the fault current during fault conditions. Due to the low impedance, there is a sharp increase in fault current, necessitating an enhanced protection strategy, which ensures that the system is adequately protected. This paper introduces a coordinated protection strategy specifically designed for distributed electric aircraft propulsion systems to mitigate or prevent short-circuit faults. The proposed algorithm utilizes an I2t-based strategy and the current-limiting-based strategy to protect the system from short-circuit faults and overload conditions. Redundant backup protection is also included in the algorithm in case the circuit breaker fails to operate.

Definite time over-current protection on transmission line using MATLAB/Simulink

This paper has investigated the application of the definite time over-current (DTOC) which reacts to protect the breaker from damage during the occurrence of over-current in the transmission lines. After a distance relay, this kind of over-current relay is utilized as backup protection. The overcurrent relay will provide a signal after a predetermined amount of time delay, and the breaker will trip if the distance relay does not detect a line failure. As a result, this over-current relay functions with a time delay that is just slightly longer than the combined working times of the distance relay and the breaker. This DTOC is tested for various types of faults which are 3- phase fault occurring at load 1, 3-phase fault occurring at load 2, a 3-phase fault occurring before primary protection, and the behaviour of voltage and current with a failed primary protection. All the results will be obtained using the MATLAB/Simulink software package.

An Adaptive Coordinated Wide-Area Backup Protection Algorithm for Network Topology Variability

An Adaptive Coordinated Wide-Area Backup Protection Algorithm for Network Topology Variability

مرحل حماية المسافة وتأثير MOV على مناطق المرحل بإستخدام الماتلاب

Transmission lines are an important part of the power system. Transmission lines are used to transmit power and are prone to many breakdowns. Therefore, protection relays are used to protect transmission lines. The purpose of the protection system is to isolate the faulty part from the healthy part, because large currents generated by faults may cause damage to electrical equipment. One of the protection relays is the distance relay and is mainly used in the transmission line. Sometimes these relays are used for backup protection. Distance relays to determine impedance need voltage and current. Transmission lines are usually protected by a distance protection relay. Distance relays are of the high-speed class and can provide transmission lines. Protection distance relays that use impedance measurements to determine the presence and location of faults, are "fooled" by a series capacitor mounted on the line, when the presence or absence of a capacitor in the fault circuit is not known in advance. This is because the capacitor cancels or compensates for some of the line inductance, so the relay may sense a fault in its first region when the fault is actually in the second or third region of the protection. Similarly, Zone one fault can be considered reverse faults. In fact, this can cause some costly operating errors. Series compensated lines are protected from overvoltage by metal-oxide-varistors (MOVs) connected in parallel with the capacitor bank. The nonlinear characteristics of MOV devices add complexity to fault analysis and distance protection operation. During faults, the impedance of the line is modified by an equivalent impedance of the parallel MOV/capacitor circuit. Worth noting is a method that determines the L and C string values of the font and the MOV effect at the time of the error. This is done by analyzing the synchronous and sub-synchronous content of the voltage and current signals separately which provides enough information to calculate the L and C series of the line. In this paper, the transmission line impedance Z, Z(f) as a function of frequency has been calculated and plotted by the sequence characteristics and the studied MOV effect on line protection and fault location. Proper operation of the distance protection relay is also shown, and its effect on relay regions. Keywords: Distance protection relay, transmission line, zones of relay, MOV.

A Backup Protection Based on Compensated Voltage for Transmission Lines Connected to Wind Power Plants

Due to the influence of complex control, the short circuit current provided by wind power generation units will exhibit new characteristics, such as limited amplitude and controlled phase, affecting the performance of traditional protections. This paper analyzes the work principle and defects of one kind of multiphase compensated distance protection. Drawing on the idea of fault identification by multiphase compensated distance protection, novel pilot protection using the compensated voltage on both sides is proposed. The proposed method has a strong anti-fault resistance ability. The test results indicate that the proposed method can distinguish the internal faults and external faults reliably, unaffected by the new characteristics of short circuit current.

Coordination Tool for Overcurrent and Earth-Fault Relays at A 33/11 KV Power Distribution Substation in Basrah City

The coordination of overcurrent relay protection in the power framework is crucial for preserving electrical distribution systems. It ensures that both primary and backup protection are provided to the system. It is essential to maintain a minimal level of coordination between these relays in order to reduce the overall running time and guarantee that power outages and damage are kept to a minimum under fault conditions. Proper coordination between the primary and back-up relays can minimize the operation duration of overcurrent with instantaneous and earth fault relays by selecting the optimum TMS (Time Multiplier Setting) and PS (Plug Setting). The present study investigates the difficulty associated with determining the TMS and PS values of earth-fault and overcurrent relays at the 33/11 kV power distribution substation in Basra using the instantaneous setting element. Overcurrent and earth fault relays were simulated in two scenarios: one with a time delay setting and one with an immediate setting. This procedure was carried out to generate Time Current Characteristics (TCC) curves for each Circuit Breaker (CB) relay took place in the Nathran substation, which has a capacity of 2×31.5 MVA and operates at a voltage level of 33/11 kV. The substation is a part of the Basrah distribution network. The short circuit current is estimated at each circuit breaker (CB), followed by the simulation of protection coordination for the Nathran substation using the DIgSILENT Power Factory software. This research is based on real data collection, and the setting considers the short-circuit current at the farthest point of the longest feeders. The results show the effectiveness of the proposed coordination scheme, which reduced trip operation time by 20% compared to the presented case study while maintaining coordination between primary and backup protection.

A reliability‐based construction approach for wide‐area backup protection systems utilizing phasor measurement units in smart grids

AbstractReliability is a fundamental requirement of wide‐area backup protection (WABP) systems, and it is one of the most crucial performance indicators for such a WABP system. Two definitions are introduced: the reliability of WABP systems and the undetectable probability of a power line. They are determined by the specific placement of communication links (CLs) and phasor measurement units (PMUs). A simultaneous optimization model was developed to minimize the construction cost of WABP systems by optimizing the partitioning and placement of PMUs, protection centers, and CLs. The model considers several constraints, including latency, regional balance, and system reliability. To reduce the computational complexity, a cluster‐based genetic algorithm was developed to determine the optimal solution. Finally, numerical simulations were conducted using IEEE test cases. The results demonstrate that the proposed method can minimize the construction costs of WABP systems while increasing their reliability.

Real-Time Co-Simulation for the Analysis of Cyber Attacks Impact on Distance Relay Backup Protection

Smart Grid is a cyber-physical system that incorporates Information and Communication Technologies (ICT) into the physical power system, which introduces vulnerabilities to the grid and opens the door to cyber attacks. Wide area protection is one of the most important smart grid applications that aims at protecting the power system against faults and disturbances, which makes it an attractive target to cyber attacks, aiming at compromising the reliability of the power system. Understanding the interaction between the cyber and physical components of the smart grid and analyzing the damage that cyber-attacks can do to wide area protection is very important as it helps in developing effective mitigation approaches. This paper evaluates the impact of cyber attacks on a wide area distance relay backup protection scheme in real-time, through the development of a co-simulation platform based on Real Time Digital Simulator (RTDS) and network simulator 3 (NS3) and using the IEEE-14 bus power system model.

Accelerated Backup Protection for UHV Long-Distance Hybrid Cascaded DC Transmission Lines

Accelerated Backup Protection for UHV Long-Distance Hybrid Cascaded DC Transmission Lines

Inverse-time Backup Protection Based on Unified Characteristic Equation for Distribution Networks with High Proportion of Distributed Generations

Inverse-time Backup Protection Based on Unified Characteristic Equation for Distribution Networks with High Proportion of Distributed Generations

Coordination of protection and operation in micro-grids with inverter based distributed generation using SAOA.

In the proposed protection coordination scheme, the depreciation of the operation time of the entire relay in the primary and backup protection modes for all possible fault locations is considered as the objective function. The limitations of this problem include the equations for calculating the operation time of the relays in both forward and reverse directions, the limitation of the coordination time interval, the limitation of the setting parameters of the proposed relays, the restriction of the size of the reactance that limits the fault current, and the limitation of the standing time of distributed generation per small signal fault. The operation time of the relays depends on the short circuit current passing through them, so it is necessary to calculate the network variables before the fault occurs. For this purpose, optimal daily power distribution should be used in the micro-grid, because micro-grids consist of storage and renewable resources. The proposed plan includes the uncertainties of consumption and generation capacity of renewable resources. Then, to achieve a reliable answer with a low standard deviation, the refrigeration optimization algorithm is used to solve the proposed problem. Finally, the proposed design is implemented on the standard test system in the MATLAB software, and then the capabilities of the proposed design are examined.

A Communication-Assisted Distance Protection for AC Microgrids considering the Fault-Ride-Through Requirements of Distributed Generators

The conventional overcurrent protection is ineffective in isolating faults in microgrids due to the low fault current levels contributed by inverter-interfaced distributed generations (IIDGs). To extend the microgrid protection methods, the distance protection is considered as a common alternative to detect faults. However, the fault-ride-through (FRT) requirements and the high impedance fault (HIF) detection challenge the application of the conventional distance protection. To solve the two problems, a new inverse-time distance (ITD) protection for medium-voltage AC microgrids was proposed in this paper. The primary ITD protection was designed to meet the FRT requirements, and the backup protection was coordinated to isolate faults. The fault resistance and distributed generation infeed effect on the measured impedance were mitigated by a communication-assisted method proposed in this paper. Owing to the shorter communication channel time in distribution feeders and lower communication investments without a synchronous clock, the proposed method can be used to improve the ITD protection performance. An 11 kV AC microgrid was simulated with different fault types in the islanded mode and grid-connected mode. Time domain simulation verified the effectiveness of the proposed ITD protection.