Adaptive Protection Scheme Research Articles

Adaptive protection scheme for microgrids

Micro grids are gaining attention to become an integral part of traditional power system, due to their numerous technical benefits and their ability to improve power system reliability.Voltage regulation, reduction in Transmission and distribution losses, reduction in the need for transmission capacity addition etc are the few technical benefits of micrgrids with renewable energy sources. However, a protection scheme that suits a conventional power system will require a major revamp if micro grids need to be interfaced. The power generations of each renewable source, mode of operation of microgrids are the few important factors to be considered to fix the relay settings. The conventional over current protection scheme faces selectivity and sensitivity issues during the grid faults and the microgrid faults, since the fault current level is different in both the cases. Hence, electro mechanical and static relays may not be suitable for the protection of power systems with microgrids. The processor based relays with augmented intelligence, that is, a relaying scheme which can act according to the operating condition need to be developed. This paper proposes an adaptive protection scheme for power systems with microgrids. The proposed method in this paper is tested with a hardware prototype resembles the actual microgrid setup.

An adaptive directional current protection scheme for distribution network with DG integration based on fault steady-state component

In view of the low reliability of traditional protection in the distribution network caused by the massive integration of DGs (distributed generation), an adaptive directional current protection scheme based on fault steady-state component is proposed in this paper. First, by analyzing the fault transient characteristics and fault equalization methods of different types of DGs, the components of system short circuit current are calculated, and the relationship between three phase components of the short circuit current is revealed. On this basis, according to the fault boundary conditions, the fault steady-state components are obtained. And then, combined with the measured voltage and measured current at the relaying point, the equivalent voltage and equivalent impedance at the backside of protection are calculated. Thus the adaptive directional current protection criteria for different fault types are formed. Simulation results demonstrate that, the proposed scheme is not affected by the type and power output of DG and the system operation mode, and could effectively prevent the protection from refusing to operate due to voltage drop.

Proposition of an Adaptive Protection Scheme for Distribution Systems with Distributed Generation

An adaptive protection scheme for distribution systems with insertion of distributed generation is proposed, which is based on the implementation of an algorithm that automatically selects previously calculated protection settings and intentionally placed in slots, which store the relay configurations, associating them with the corresponding scenario. The algorithm was analyzed in a test system implemented in a real-time simulator and at the end, the results showed that the proposed algorithm presents superior performance than the conventional protection.

A Review of Communication Failure Impacts on Adaptive Microgrid Protection Schemes and the Use of Energy Storage as a Contingency

A main challenge in the practical implementation of a microgrid is the design of an adequate protection scheme in both grid-connected and islanded modes of operation. Microgrid protection requires a fast, reliable, and robust communication system to adjust relay settings to the appropriate current level according to the operation mode. Various approaches have been implemented to deal with this problem, yet the most promising ones are the use of adaptive protection techniques abiding by the International Electrotechnical Commission (IEC) 61850 communication standard. This paper presents a review of the technical challenges for the use of classical protection techniques and the need for an enhanced, adaptive, smart protection system. However, the risk of communication link failures and cyber security threats still remain a challenge in implementing a reliable adaptive protection scheme. A contingency is essential in the event that a communication failure prevents a relay from adjusting between grid-connected and islanded mode. An adaptive protection scheme is proposed, which utilizes energy storage devices to enhance resiliency against communication outages. The proposed solution does not incur additional costs to the network, as the energy storage devices are already utilized for other purposes. A case study experimentally verifies this contingency under a worst-case scenario, where a fault occurs simultaneously with a pulsed load while operating in islanded mode with a communication failure.

Design of an adaptive overcurrent protection scheme for microgrids

Microgrid is a new phenomenon regarded to Distributed Generation (DG) penetration in the existing distribution systems. In this paper adaptive over current (OC) protection technique for a distribution system with DG penetration is proposed. This scheme takes into account general protection requirements, impacts of DG on protection system and protection coordination. A part of IEEE 13 nodes radial distribution test feeder is taken as a study case to test the effectiveness of the proposed scheme using ETAP software.Keywords: Distributed Generator, Microgrids, Adaptive overcurrent protection, Protection Coordination

An Adaptive Overcurrent Coordination Scheme to Improve Relay Sensitivity and Overcome Drawbacks due to Distributed Generation in Smart Grids

Distributed generation (DG) brought new challenges for protection engineers since standard relay settings of traditional system may no longer function properly under increasing presence of DG. The extreme case is coordination loss between primary and backup relays. The directional overcurrent relay (DOCR), which is the most implemented protective device in the electrical network, also suffers performance degradation in the presence of DG. Therefore, this paper proposes the mitigation of DG impact on DOCR coordination employing adaptive protection scheme (APS) using differential evolution algorithm while improving overall sensitivity of relays. The impacts of DG prior and after the application of APS are presented based on interconnected 6 bus and IEEE 14 bus system. As a consequence, general sensitivity improvement and mitigation scheme is proposed.

A novel adaptive distance protection scheme for DFIG wind farm collector lines

In view of the sensitivity and selectivity problems in DFIG (doubly-fed induction generator) wind farm collector line protection, a new adaptive distance protection scheme is proposed. First, according to the geometric distribution characteristics of the collector line voltage and current, the equation of voltage drop from the relaying point to the fault point is established and the adaptive setting coefficient is calculated. On this basis, a new adaptive distance protection criterion is formed according to the phase relationship between the fault current and the measured current. Wind farm simulation tests on RTDS verify that, the proposed method is well adaptable to different operation modes, strongly immune to the fault resistance and unaffected by the weak feed characteristics of the wind generator collector system.

Modeling and Experimental Verification of a 100% Stator Ground Fault Protection Based on Adaptive Third-Harmonic Differential Voltage Scheme for Synchronous Generators

In this paper, a novel adaptive stator-ground fault protection scheme based on third-harmonic differential voltages is implemented on a lab scale synchronous generator. The lab scale generator is used to emulate the fault characteristics of industrial generators along the stator windings. Simulations based on finite element analysis methods were used to design and tune the laboratory testbed. Experimental results prove the expected fault characteristics as well as fault detection capability of the adaptive stator-ground fault protection scheme.

Effects of Distributed Generation on Overcurrent Relay Coordination and an Adaptive Protection Scheme

Integration of distributed generation (DG) such as renewable energy sources to electrical network becomes more prevalent in recent years. Grid connection of DG has effects on load flow directions, voltage profile, short circuit power and especially protection selectivity. Applying traditional overcurrent protection scheme is inconvenient when system reliability and sustainability are considered. If a fault happens in DG connected network, short circuit contribution of DG, creates additional branch element feeding the fault current; compels to consider directional overcurrent (OC) protection scheme. Protection coordination might get lost for changing working conditions when DG sources are connected. Directional overcurrent relay parameters are determined for downstream and upstream relays when different combinations of DG connected singular or plural, on radial test system. With the help of proposed flow chart, relay parameters are updated and coordination between relays kept sustained for different working conditions in DigSILENT PowerFactory program.

Adaptive distance protection scheme with quadrilateral characteristic for extremely high‐voltage/ultra‐high‐voltage transmission line

Traditional distance protection may mal-operate or refuse to operate in the case of non-metallic faults, endangering the safety of power system. Therefore, a new adaptive distance protection scheme based on the impedance complex plane is proposed in this study. First, by utilising the phase relationship between the negative sequence current at the relaying point and the current at the fault point, the fault supplementary impedance angle caused by the fault resistance is calculated. Then, the effective fault impedance from the fault point to the relaying point is obtained by the trigonometric function relationship of the effective fault impedance, measured impedance and fault supplementary impedance on the impedance complex plane. On this basis, the criterion of the adaptive distance protection is constructed. Finally, test results on real-time digital simulator demonstrate that the protection scheme proposed in this study is applicable to various types of faults, and has a good adaptability to different system operating conditions. Compared with traditional distance protection scheme, the proposed scheme is immune to the fault resistance, thus mal-operation or operation-rejection of distance protection caused by the fault resistance could be effectively avoided.

Minimizing the impact of distributed generation of a weak distribution network with an artificial intelligence technique

Integration of renewable energy sources directly into the distribution network become a common practice nowadays, the contribution of renewable energy sources to the distribution network predominate by weather conditions which change short circuit level capability for the electric network. This change in the network configuration could influence the operation of the protective devices in the distribution network. In this study, an online adaptive protection scheme base on adaptive fuzzy algorithm proposed to update and optimize the protection coordination when network topology has been changed. The online algorithm depends on different parameters such as the status of main feeder circuit breaker and the prefault power flow in the network. The simplified network represents a portion of the Eastern Libyan Electric Network implemented in ETAP package.

Hardware-In-the-Loop Design and Optimal Setting of Adaptive Protection Schemes for Distribution Systems With Distributed Generation

The constantly increasing presence of distributed generation (DG) in modern distribution systems induces grid configuration alterations, affecting thus the short-circuit levels and fault current paths. To address all arising protection challenges, adaptive protection is being implemented. This paper presents an innovative hardware-in-the-loop adaptive protection scheme, which incorporates real-time simulation, multifunction protection, centralized control, and optimal calculation of protection settings. The proposed adaptive scheme is based, first, on the determination of optimal relay setting groups, and then on their online self-adjustment, providing a continuously tuned protection scheme to the variable system operating modes. The efficacy of the proposed solution is demonstrated through two distribution test networks with embedded DG.

An Adaptive Protection Scheme for Distribution Systems With DGs Based on Optimized Thevenin Equivalent Parameters Estimation

This paper proposes an adaptive protection scheme for distribution systems with distributed generations (DGs). To mitigate the influences on the protection devices by DGs, an online calculation method of fault current under various system operation conditions is presented. By sampling local available measurements in the buses, a proposed optimized estimation method is used to calculate the Thevenin equivalent circuit parameters of the system dynamically. Moreover, the short-circuit current can be calculated accurately to set the overcurrent relay protection value considering the behavior of DGs during the fault. To ensure the accurate operation of the protection devices, a coordinated protection scheme, including primary and backup protection is presented. Performances of the proposed method and scheme have been verified by simulations on a sample distribution system based on PSCAD/EMTDC. The sensitivity and selectivity of the coordination between primary and backup protection are satisfied under different system operation conditions, fault locations, and types.

Utilizing supercapacitors for resiliency enhancements and adaptive microgrid protection against communication failures

Islanded microgrids do not have sufficient resources to contribute enough fault current to legacy protection devices to continue operation. Therefore, when a fault happens in an islanded microgrid, relays with high fault current setting will fail to detect and clear the fault. Contemporary adaptive protection schemes rely on communication technologies to adjust the relay settings to adapt to the microgrids’ modes of operation; grid-connected or islanded. However, the risk of communication link failures and cyber security threats such as denial-of-service represent major challenges in implementing a reliable adaptive protection scheme. In order to address this issue, this paper proposes an adaptive protection scheme which utilize super capacitive energy storage to enhance resiliency against communication outages. This paper also introduces an autonomous control algorithm developed for the super-capacitor’s AC/DC converter. The proposed control is capable of deciding upon charging, discharging of the super-capacitor, and whether or not to feed fault currents in the AC side, based on direct voltage and frequency measurements from its connection point with the microgrid. This eliminates the need for a control command to be sent from the point of common coupling of the microgrid with main grid to adjust the controller’s mode of operation and thus reducing the risk of controller failure due to cyber-attacks or other communication issues. Additionally, the paper proposes a solution to avoid installing a larger super-capacitor by temporarily disconnecting the uncritical pulsed load during the fault instant. The proposed protection scheme was investigated through simulation for various fault types and showed successful results using the proposed scheme in eliminating the aforementioned faults when the communication were available or attacked.

Adaptive voltage protection scheme based on wide area information

An adaptive voltage protection scheme based on wide area information is proposed in this study. The method uses intelligent electronic device (IED)s to acquire real-time voltage and current information and store relevant line parameters, thus realise communication between primary and backup protection devices. On this basis, adaptive primary and backup voltage protection is structured. Simulation results show the setting value is adaptive to different system operation mode and distributed generation (DG) output. The time to issue the tripping command will not be affected by the variation of DG output and fault type. Compared with traditional voltage protection, the proposed adaptive voltage protection scheme effectively extends the protection range.

Fuse relay adaptive overcurrent protection scheme for microgrid with distributed generators

Utilities have installed distributed generators to improve reliability of the power distribution system. Distributed generators at various sites provide additional circuit paths in case energy provision to the end user is interrupted by a blackout or equipment failure. When the microgrid is working on island and grid-connected modes, overcurrent protections in power lines must be adjusted to different distributed generator circuit paths and feeder fuses in the microgrid. This study presents an adaptive overcurrent protection that integrates technical and economic advantages of fuses and relays in a microgrid with distributed generators. This fuse relay adaptive overcurrent protection (FRAOP) scheme protects power lines and feeders by grouping identical inverse time overcurrent settings of relays, and logic gates of relay's breakers. Selectivity, reliability, and speed of the FRAOP was verified by a real-time simulator with relays in-the-loop.

Adaptive threshold based new active islanding protection scheme for multiple PV based microgrid application

A new adaptive active islanding protection scheme is presented for a multiple photovoltaic (PV) based microgrid environment, where islanding detection parameters are estimated in adaptive manner according to operational PV penetration level. Dynamic threshold calculation is obtained by a piecewise cubic Hermite polynomial interpolation to detect islanding for a PV based voltage source converter (VSC), where inconsistent solar irradiation profile is subjected to the system connected to local utility through point of common coupling (PCC). The VSC pulse-width modulation inputs are obtained from primary second-order phase locked loop based control path, where instability to detect islanding is achieved by active injection of error dynamics (parallel islanding protection path). The disturbance injection is decided from islanding detection parameter (i.e. harmonic amplification factor, %HAF) of PCC voltage and the VSC instability is achieved by desired unstable closed-loop poles of parallel detection path. UL 1741 standard is considered for the proposed multi-PV microgrid, for worst-case scenario study.

Adaptive protection scheme for distributed systems with DG

Adaptive protection scheme for distributed systems with DG

Adaptive protection scheme for smart microgrid with electronically coupled distributed generations

This paper aims at modelling an electronically coupled distributed energy resource with an adaptive protection scheme. The electronically coupled distributed energy resource is a microgrid framework formed by coupling the renewable energy source electronically. Further, the proposed adaptive protection scheme provides a suitable protection to the microgrid for various fault conditions irrespective of the operating mode of the microgrid: namely, grid connected mode and islanded mode. The outstanding aspect of the developed adaptive protection scheme is that it monitors the microgrid and instantly updates relay fault current according to the variations that occur in the system. The proposed adaptive protection scheme also employs auto reclosures, through which the proposed adaptive protection scheme recovers faster from the fault and thereby increases the consistency of the microgrid. The effectiveness of the proposed adaptive protection is studied through the time domain simulations carried out in the PSCAD⧹EMTDC software environment.

Improving the performance of power system protection using wide area monitoring systems

Wide area monitoring (WAM) offers many opportunities to improve the performance of power system protection. This paper presents some of these opportunities and the motivation for their development. This methods include monitoring the suitability of relay characteristics, supervisory control of backup protection, more adaptive and intelligent system protection and the creation of novel system integrity protection scheme. The speed of response required for primary protection means that the role WAM in enhancing protection is limited to backup and system protection. The opportunities offered by WAM for enhancing protection are attractive because of the emerging challenges faced by the modern power system protection. The increasingly variable operating conditions of power systems are making it ever more difficult to select relay characteristics that will be a suitable compromise for all loading conditions and contingencies. The maloperation of relays has contributed to the inception and evolution of 70 % of blackouts, thus the supervision of the backup protection may prove a valuable tool for preventing or limiting the scale of blackouts. The increasing interconnection and complexity of modern power systems has made them more vulnerable to wide area disturbances and this has contributed to several recent blackouts. The proper management of these wide area disturbances is beyond the scope of most of the existing protection and new, adaptive system integrity protection schemes are needed to protect power system security.