Adaptive Differential Protection Research Articles

Adaptive Quasi-Power Differential Protection Scheme for Active Distribution Networks

With the massive integration of distributed generations (DGs), distribution networks gradually become more active and flexible. Conventional overcurrent protection is difficult to adapt to such active distribution networks (ADNs). Current differential protection (CDP) is a good choice for solving this issue, but the multi-branch structure of ADNs especially the unmeasured T-connected load branch affects the protection’s sensitivity. Therefore, the paper proposes a quasipower differential protection (QDP) scheme based on Tellegen’s theorem. First, the feasibility of applying Tellegen’s theorem to ADNs was analyzed. On this basis, reasonable protection criteria were designed for different scenarios of ADNs. Then, an adaptive protection scheme was established, which can automatically adjust the criteria depending on the presence of Tconnected branches within the protected section. Finally, extensive simulations were carried out in an ADN model using PSCAD/EMTDC software. The simulation results demonstrate that the proposed protection scheme has excellent adaptability to network topologies, fault types, fault resistances, and network structures of ADNs.

Phase-angle adaptive current differential protection for active distribution network

With the distributed generator to be attached to the distribution network, the current differential protection scheme may have some problems, resulting in maloperation or rejection of protection. This paper investigates the current distribution properties of an active distribution network with branches of undetected load and draws the conclusion that undetected load may cause differential protection maloperation. The differences in fault properties of differential protection in transmission network scenarios and distribution networks containing distributed generator are evaluated, leading to the conclusion that differential protection applied to active distribution networks may have reduced resistance to transition resistance and that poor signal synchronization conditions in distribution networks may lead to larger synchronization errors. A phase-angle adaptive current differential protection is proposed. It adaptively adjusts the phase angle constraint using the magnitude of the power frequency full current component proportion at both sides of the line. It can accommodate the protection needs of various operation modes of distribution networks containing distributed generator, and has the characteristics of strong resistance to transition resistance and strong phase shift braking ability. The correctness of the suggested protection scheme was verified using the PSCAD platform.

Adaptive additional current-based line differential protection in the presence of converter- interfaced sources with four quadrant operation capability

As typical representatives of converter-interfaced sources with four quadrant operation capability, battery energy storage station (BESS) and VSC-HVDC station behave differently with synchronous generator. This leads to the high risk of incorrect operation of current differential protection (CDP), seriously threatening the security of transmission network. Motivated by this issue, this paper presents adaptive additional current-based differential protection (AAC-DP). Adaptive additional current is introduced to modify the criterion of current differential protection. Ulteriorly, the unified expression of adaptive additional current for internal and external faults is designed. Adaptive additional current can increase the sensitivity during internal fault, whereas it improves the security during external fault. The sensitivity and dependability of AAC-DP was widely evaluated by changing operation mode, fault condition, and type of power source using PSCAD and RTDS-based experimental platform. Also, the adverse factors, such as saturation and error of current transformer(CT), and noise, were taken into account; thereof, the excellent security of AAC-DP was confirmed. The results confirm that AAC-DP exhibits excellent performance in operating speed, sensitivity, the adaptation to fault behaviors of BESS and VSC-HVDC, and robustness against saturation and error of CT, and noise.

Transformer differential protection scheme based on self‐adaptive biased characteristic curve and considering cross‐country faults

AbstractThe differential protection of transformers sometimes does not have reliable performance facing some faults and events such as saturation of current transformers (CTs) during internal and external faults, inrush currents, and cross‐country faults (CCFs). In this paper, a new transformer differential protection scheme based on the self‐adaptive biased characteristic curve and considering CCFs and various disturbances are used. First, the maximum overlap discrete wavelet transform (MODWT) was used to extract the superior characteristics of sampled differential current of the transformer at different levels. Then, by calculating the duty cycle (D) values of energy coefficients extracted in each periodicity by MATLAB software, a new self‐adaptive biased characteristic curve will be obtained in different operating conditions. Finally, the percentage differential protection operation is adjusted based on the new adaptive characteristic curve zones. Differential current sampling under different operating conditions was performed on a real three‐phase transformer in EMTP software. The simulation results show that the proposed adaptive differential protection scheme can accurately detect various faults and events occurring in the transformer and increase system reliability.

Adaptive current differential protection for active distribution network considering time synchronization error

To solve the impact of the integration of distributed generations on distribution network protection, current differential protection is introduced into the active distribution networks. Using fault data self-synchronization algorithm to construct current differential protection can reduce the cost of protection and communication, but the unsynchronized starting of relays on both sides will cause time synchronization errors and affect the reliability of protection, especially when high resistance faults occur at feeders with inverter-based DGs. In this paper, the cause of the starting delays of protective relays is analyzed through assumptions and approximations. On this basis, an adaptive current differential protection method for active distribution networks is proposed. This method uses the current amplitude ratio on both sides of the protected feeder to adaptively modify restraint current in differential protection, which can weaken the effect of time synchronization error caused by fault data self-synchronization algorithm and improve the performance of current differential protection. Finally, the effectiveness of the proposed method is verified in both PSCAD/EMTDC simulation and a closed-loop test platform based on the real-time digital simulator.

Protection of active distribution networks incorporating microgrids with multi-technology distributed energy resources

The protection of active distribution networks incorporating microgrids with high penetration of Distributed Energy Resources (DERs) can be challenging if traditional protective relays are used. This is mainly due to the changes in the power flow, fault current level, difficulty in protection coordination, changes in system topology, and system operating conditions. This paper proposes three new protection algorithms for active distribution networks with large penetration level of inverter-based DERs. These protection algorithms comprise of an adaptive differential protection algorithm, incremental transient energy-based directional protection, and a rate-of-change of current protection. The proposed protection algorithms were tested with a distribution network integrated with wind, solar, diesel generator, and battery storage DERs which are capable of operating in islanded mode forming local microgrids. The distribution system and the proposed protection functions modelled and simulated using the Real-Time Digital Simulator (RTDS®). The results obtained from tests validate the proposed algorithms; and their capability to correctly detect and timely isolate faults without resulting in nuisance tripping of the DERs.

Adaptive Differential Protection System for Microgrid

Microgrids are the small version of power system which grants us the integration of distributed generation resources to insure the facilities to the remotely located electric loads as well as have so many advantages over traditional power system like reduced transmission loss, green energy solution and proper use of renewable energy resources. However the resilience offered by microgrid is inconvenient if it is not be able to protect properly in case of any disturbance occurs which is very common in microgrid due to load dynamics. Protective devices used in traditional power grid cannot actually protect microgrid due to variable loads and different fault levels at grid connected modes and islanded modes. The available research about this concern has not been very successful, therefore options like distance, directional over current and differential relay remains effective protection scheme from present standard. Even though these relays are very useful in power system but their effectiveness for microgrid is yet to be analyzed. This paper is presenting the MATLAB simulation based analysis for differential relay type adaptive protection system by taking a complex microgrid model and generating various fault and generation capacities and analyzing it. In this paper different scenarios has been discussed where differential relay seems to be better than distance and directional over current relay protection scheme.

Development of an adaptive differential protection scheme for transformer during current transformer saturation and over‐fluxing condition

Development of an adaptive differential protection scheme for transformer during <scp>current transformer</scp> saturation and over‐fluxing condition

Adaptive differential protection scheme for wind farm integrated power network

In this paper, an adaptive differential protection scheme is proposed for wind farm integrated power network. Any fixed threshold setting based protection scheme is not always suitable for the different operating conditions of power system. Considering the possible modulations in the fault signal, a particle swarm optimization (PSO) based differential relay algorithm is proposed in this paper. The positive sequence current differential principle is used. For different operating conditions, fault conditions and configurations of the system, the threshold value can be calculated online. So, practically the method can be applied to any power system model and the impact of dynamic operation of wind farm on the protection function is negligible. The threshold setting is designed considering the fault location and fault inception angle. Initially, the most effective faults among all the possible faults are identified with a single variable (fault location) objective function. Later, only single-phase-to-ground fault is considered for threshold setting with all possible parameters. The method is tested using a standard power system model integrated with wind farm and simulated using MATLAB R2016a software. Results prove the efficacy of the method.

Swarm intelligence-based differential protection scheme for wind integrated transmission system

Conventional differential protection scheme considers a fixed threshold to detect the fault in a transmission system. In a wind integrated transmission system, any fixed threshold-based protection function is not reliable always due to the dynamic variation of control parameters of the wind turbine. To mitigate this issue, an adaptive differential protection scheme is proposed in this work for the transmission system integrated with wind farm. The method uses a particle swarm optimization (PSO) algorithm to generate an optimum threshold for the system considering the varying system and fault operating conditions. An objective function is designed for PSO considering the fault location, inception angle, and fault resistance. The method is tested by using a standard wind integrated transmission system model, simulated using MATLAB software. Performance of the method is tested for numerous test cases considering the wide variations in fault and system operating conditions.

Real-Time Adaptive Differential Feature-Based Protection Scheme for Isolated Microgrids Using Edge Computing

Inhabited isolated areas require independent power systems called isolated microgrids. Conventional protection schemes are not suitable for isolated microgrids due to their dependence on significant fault current. This article introduces an adaptive differential feature-based protection scheme for fault detection and faulty phase identification for isolated microgrids. Instead of differential currents, it proposes differential features, where edge computing is used to extract the features at point of measurement. The most informative one-dimensional feature is extracted from each phase at both ends of the line. The line differential feature is compared with an adaptive threshold to perform fault detection. The threshold is updated every second and is immune to system noises. Faulty phase identification is performed with a logical comparison. An in-memory circular buffer is proposed to store the local features in case of communication delay. Communication and synchronization are experimentally validated, and the worst-case latency is reported along with individual processing time for data acquisition, feature extraction, communication, and fault detection. Extensive validations are done with IEC-based and IEEE 13-node-based isolated microgrid. The test results are compared with state-of-the-art methods and proved that the proposed scheme is practical to be adopted in real- world isolated microgrids of different sizes and topologies.

An Adaptive Differential Protection and Fast Auto-Closing System for 10 kV Distribution Networks Based on 4G LTE Wireless Communication

With the development of wireless communication technology and computer technology, more and more smart technologies have been applied in electricity distribution networks. This paper presents an adaptive current differential protection and fast auto-closing system for application in 10 kV distribution networks in China Southern Power Grid. The current differential protection can adaptively change its settings according to the topology change of the primary distribution networks, thus the system effectively reduces the operation and maintenance cost of the power distribution network. In order to restore the power supply for the healthy part of the 10 kV networks quickly after a power system fault is cleared, the protection and control system provides wide area control function for automatic fault isolation and automatic switching. The traditional overcurrent protection and control system have no fault location function, it may take several minutes or even hours to manually locate a fault and then restore the power supply. Compared with the protection and control system of the traditional 10 kV distribution networks, the system developed can locate and isolate faults within 900 ms (assuming that the operating time of the load switch is 700 ms), and can quickly restore power supply in less than one second after a power system fault is cleared.

Real-Time Monitoring &amp; Adaptive Protection of Power Transformer to Enhance Smart Grid Reliability

Abstract Power transformer is one of the most important pieces of equipment in the grid to reliably and efficiently transmit power to the consumers. Asset management and protection are the best concepts for prolongation of transformer lifespan as well as for the increase of grid reliability. This article presents electrical and non-electrical parameter-based power transformer monitoring and protection. Various data such as core flux, age of asset, heat generation, current harmonics and temperature are monitored in real time and processed accordingly to enhance the working capability of the transformer. The proposed scheme is successfully tested on 15 kVA laboratory transformer using Arm CORTEX-M4 processor. A Fitness Function (Ff) is estimated from the collected data to examine the working condition of the transformer. Moreover, voltage, current and power-based inrush detection as well as Adaptive Power Differential Protection (APDP) are applied to protect the transformer against fault. The hardware implementation and result validation prove the effectiveness of the proposed scheme in enhancing reliability of the distribution grid.

Adaptive differential protection for transformers in grid-connected wind farms

Adaptive differential protection for transformers in grid-connected wind farms

Application of a Recursive Phasor Estimation Method for Adaptive Fault Component Based Differential Protection of Power Transformers

An adaptive differential protection method is proposed for power transformers. First, the phasors of captured current signals are computed using an online recursive S-transform-based method of phasor estimation with low computational burden. Then, the fault components of currents are calculated as a measure of disturbance severity. The relay employs the fault components of the restraint and differential currents to adjust slopes and pickup settings of its dual-slope characteristic curve according to the disturbance, and discriminates external and internal faults. To avoid malfunctions caused by inrush currents, an average power based index is also proposed, which has high values during inrush currents while it is near zero for faulty cases. The proposed method is implemented using MATLAB and electromagnetic transients program (EMTP) software packages and its performance is compared with the multiregional and self-adaptive approaches. In addition, real-data records of two differential relays located in the South West Interconnected System in Western Australia have also been used to determine the accuracy of the proposed power transformer protection algorithm. Both the simulation and the real data test results show that the proposed method is more reliable and secure for faulty and nonfaulty cases in analogy to the other two protection approaches.

A New Adaptive Differential Protection Scheme for Tap Changing Power Transformer

Abstract This paper presents a new adaptive differential protection scheme which efficiently adapts the change in tap position of a power transformer. The proposed scheme is based on analytical derivation of pick-up and slope of the differential relay characteristic. By acquiring information such as rating &amp; connection of CTs and present tap position as input, the proposed scheme enhances sensitivity of differential relay during internal faults. This is accomplished either by decreasing pick-up and/or adjusting slope of the differential characteristic of the relay in case of change in tap position. Numerous test cases consisting of various types of internal and external faults have been simulated for an existing power transformer of Gujarat Energy Transmission Corporation Limited (GETCO), Gujarat, India using PSCAD/EMTDC software package. The proposed scheme increases percentage of winding to be protected during internal faults for power transformers having different ratings and connections compared to the conventional differential protection scheme. Furthermore, it has been observed that the detection sensitivity during special types of turn-to-turn and inter-winding faults with varying fault resistances is also enhanced compared to the conventional scheme. Moreover, it equally maintains stability during CT saturation condition. At the end, comparative evaluation of the proposed scheme with the existing schemes clearly indicates superiority of the proposed adaptive scheme.

Adaptive differential protection of three-phase power transformers based on transient signal analysis

This paper presents a three-phase power transformer percentage differential protection formulation based on transient signal analysis. The proposed formulation uses discrete wavelet transforms (DWT) to extract transitory features of non-stationary signals with fast transition, mapping the signal in time–frequency representation. The proposed formulation was implemented on MATLAB® environment and evaluated through a case study using BPA’S ATP/EMTP software. Comparative test results are presented showing that the proposed formulation is highly reliable, fast, accurate and easy for real-life construction.

Adaptive Agent-Based Wide-Area Current Differential Protection System

This paper proposes a multiagent-based adaptive wide-area current differential protection system. A power grid is divided into primary and backup protection zones dynamically online with the help of a developed expert system, and the relay agents of these zones cooperate to perform a differential relaying function. Predictive self-healing strategies have been proposed to prevent misoperation of the relay agent, and the communication system has been simulated. The performance of the proposed adaptive wide-area current differential protection system based on computer simulation is presented in this paper.

Adaptive Current Differential Protection Schemes for Transmission-Line Protection

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Throughout the history of power system protection, researchers have strived to increase sensitivity and speed of apparatus protection systems without compromising security. With the significant technological advances in wide-area measurement systems, for transmission system protection, current differential protection scheme outscores alternatives like overcurrent and distance protection schemes. Therefore, in this paper, we address this challenge by proposing a methodology for adaptive control of the restraining region in a current differential plane. First an error analysis of conventional phasor approach for current differential protection is provided using the concept of dynamic phasor. Subsequently, we extend the methodology for protection of series compensated transmission lines. Finally, we also evaluate the speed versus accuracy conflict using phasorlets. Electromagnetic Transient Program simulations are used to substantiate the claims. The results demonstrate the utility of the proposed approach. </para>

Universal Adaptive Differential Protection for Regulating Transformers

Since regulating transformers have proved to be efficient in controlling the power flow and regulating the voltage, they are more and more widely used in today's environment of energy production, transmission and distribution. This changing environment challenges protection engineers as well to improve the sensitivity of protection, so that low-current faults could be detected (like turn-to-turn short circuits in transformer windings) and a warning message could be given. Moreover, the idea of an adaptive protection that adjusts the operating characteristics of the relay system in response to changing system conditions has became much more promising. It improves the protection sensitivity and simplifies its conception. This paper presents an adaptive adjustment concept in relation to the position change of the on load tap changer for universal differential protection of regulating transformers; such a concept provides a sensitive and cost-efficient protection for regulating transformers. Various simulations are carried out with the Electro-Magnetic Transients Program/Alternative Transients Program. The simulation results indicate the functional efficiency of the proposed concept under different fault conditions; the protection is sensitive to low level intern faults. The paper concludes by describing the software implementation of the algorithm on a test system based on a digital signal processor.