Protection Coordination Optimization for FREEDM （Future Renewable Electric Energy Delivery and Management） System

The FREEDM （future renewable electric energy delivery and management） system is a smart distribution system that facilitates seamless integration of high-penetration DRER （distributed renewable energy resources） and DESD （distributed energy storage devices） with the existing distribution system. Protection schemes have been proposed to detect the overcurrent faults throughout the FREEDM system, according to its requirements. In this paper the time inverse directional over current protection coordination scheme is developed as a backup protection when the primary protection communication failed. The proposed scheme is applied to FREEDM network using conventional mathematical model. To speed up the fault clearing time without coordination loss, the settings of the proposed relays in the two directions are minimized using genetic algorithm. The developed methods are validated using ETAP software. The results ensure that the faults throughout the FREEDM system sections are detected and the relays tripping time are minimized.

A Novel Multi-objective Protection Coordination Scheme for a Microgrid with Optimal Deployment of Dual-setting ROCOV Based Relays

Relay coordination is crucial in electrical power systems to protect against malfunctions and damage caused by unexpected events like short circuits.To address the challenge associated with the reverse direction of fault current,dual-setting(DS)directional over-current relays have evolved but failed to provide proper coordination during changes of load,generation,and network.In the meantime,with the increasing number of DS relays,the total relay operating time tends to saturate.Therefore,this paper proposes a protection scheme based on the optimal deployment of conventional and dual-setting rate of change of voltage(DS-ROCOV)relays in distribution systems.This holds true for varying network topologies and is unaffected by variations in load and generation.The objective of the proposed scheme is to ensure reliable and efficient protection against faults in distribution systems by minimizing the overall operating time with the optimal number of DS-ROCOV relays.The proposed protection scheme’s performance is evaluated for different coordination time interval values as well as in different microgrid scenarios.This paper outlines the design and implementation of the proposed protection scheme which is validated on the modified IEEE 14-bus system using simulations in Matlab/Simulink.

Research on the protection coordination of permanent magnet synchronous generator based wind farms with low voltage ride through capability

To coordinate the protection of PMSG(permanent magnet synchronous generator),collector circuits and outgoing lines,a comprehensive and improved protection method of PMSG based wind farms with LVRT(low voltage ride through)capability is proposed.The proposed method includes adding a short time delay to the collector network current protection zone I and a directional protective relaying to the collector network protection,installing grounding transformers and zero sequence current protection,and generator low-voltage protection action improvement.A LVRT scheme consisting of variable resistance dumping circuit,grid side dynamic reactive power control and reactive power compensation control is proposed.The fault characteristics of PMSG based wind farms are analyzed,and a PMSG based wind farm in Dabancheng,Xinjiang,is used as an example to analyze typical wind farm protection configuration,the setting values considering LVRT requirements,and the coordination problems.Finally,an improved wind farm protection coordination methodology is proposed and its validity is verified by simulation.

Designing a Protection Scheme in Micro-Grid Systems with DG Using Central Protection Unite and Multiple Setting Group Protection Relays

Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.

Adaptability of the Recloser-Fuse Protection Scheme in the Presence of Distributed Generation

This paper addresses the behaviour of an IEEE(Institute of Electrical and Electronics Engineers)test network when distributed injections are added to the distribution network.The penetration of different dispersed generation technologies,modifies the distribution system characteristics,with impact on a number of parameters,depending on their size and location on the network.For this purpose,this paper comprises three case studies:in the first case an exhaustive analysis is carried out of the occurrence of faults throughout the network,along with the introduction of distributed generators;in the second case the network behavior is assessed against the use of three of the most commonly used types of generators based on rotating machines;in the third case study an evaluation is made of the network performance when the three types of DG(distributed generation)units are distributed in multiple buses.In all cases the protection system is analyzed with the aim of ensuring coordination among the protection devices.All simulations are performed using the Power Factory software package from DigSILENT.From the simulation results,conclusions are drawn that provide insights into the behaviour of protection systems,highlighting the limitations of the original protections and coordination with different distributed generators technologies.

Summary of Useful Concepts About the Coordination of Directional Overcurrent Protections

This paper summarizes some useful concepts about the coordination of directional overcurrent protections.The following key topics are described:the analysis of systems in a ring configuration and only one source of short-circuit currents;the impossibility of obtaining selectivity for all the possible system configurations with multiple sources;the need for inverse functions in order to obtain selectivity in systems with multiple sources;the coordination with protections for radial loads;the coordination between instantaneous and delayed functions;the considerations to select the pickup values;the influence of contributions from motors to short circuit currents;the transient configurations due to sequential trips at both line ends;the influence of dynamic behavior of overcurrent functions;the influence of stability constraints;other specific considerations for ground functions;some specific considerations for systems with distributed generation.A summary of these points and their effect on the coordination of directional overcurrent protections is not available in the current literature.This novel description should facilitate the inclusion of these key points in research and coordination studies related to these protective functions.

Optimized Protection Strategies for HVDC Grid with Fault-blocking Modular Multilevel Converters for Overhead Line Applications

The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy integration.Currently,two main development trends for HVDC grids are being studied:a DC breaker based HVDC grid and fault-blocking converter based HVDC grid.Although the former has a perfect performance for fault clearance,its development is still highly constrained by the cost and maturity of DC breakers.The latter can extinguish DC faults by the fault-blocking converters.Without using DC breakers,there is no bottleneck in its technical feasibility.Nevertheless,in fault scenarios,such types of HVDC grids will be blocked at length for air-deionization,which is its main drawback.The aim of this paper is to minimize its power interruption time,by optimizing protection coordination strategies.To cover the most complex cases,the overhead line applications,in which the reclosure actions are required to be implemented,are considered.In this paper,the protection requirements of HVDC grids are first discussed,then the benefits of fault-blocking modular multilevel converters(MMCs)and their fault features are analyzed.Based on this,a control function is designed to reduce the air-deionization time.To minimize the influence of the DC faults,a separation methodology for restarting the system is proposed.The effectiveness of the proposed protection coordination schemes is validated by PSCAD/EMTDC simulations.

Coordination of dual setting overcurrent relays in microgrid with optimally determined relay characteristics for dual operating modes

Fault current magnitude in a microgrid depends upon its mode of operation,namely,grid-connected mode or islanded mode.Depending on the type of fault in a given mode,separate protection schemes are generally employed.With the change in microgrid operating mode,the protection scheme needs to be modified which is uneconomical and time inefficient.In this paper,a novel optimal protection coordination scheme is proposed,one which enables a common optimal relay setting which is valid in both operating modes of the microgrid.In this con-text,a common optimal protection scheme is introduced for dual setting directional overcurrent relays(DOCRs)using a combination of various standard relay characteristics.Along with the two variables,i.e.,time multiplier setting(TMS)and plug setting(PS)for conventional directional overcurrent relay,dual setting DOCRs are augmented with a third variable of relay characteristics identifier(RCI),which is responsible for selecting optimal relay characteristics from the standard relay characteristics according to the IEC-60255 standard.The relay coordination problem is formulated as a mixed-integer nonlinear programming(MINLP)problem,and the settings of relays are optimally determined using the genetic algorithm(GA)and the grey wolf optimization(GWO)algorithm.To validate the superiority of the pro-posed protection scheme,the distribution parts of the IEEE-14 and IEEE-30 bus benchmark systems are considered.

An Intelligent Coordinated Protection and Control Strategy for Distribution Network with Wind Generation Integration

Integration of distributed generation(DG)can change the fault current level and direction in the distribution system,which affects the related protection system.In order to limit the negative impact of DG integration and upgrade the protection system performance,an intelligent coordinated protection and control strategy is proposed.A cost based optimization method is adopted to minimize the operation costs of possible solutions.Its aim is to define the optimal relay settings for the present operation condition,and the most suitable control mode of converter based wind turbine DG.Case studies on a hardware in the loop real time simulation platform demonstrate the proposed protection strategy.

Research on Coordinating Protection and Control System with Redundant Information and Distributed Computing

This paper proposes a distributed computing architecture for protection functions within a digital substation, in order to achieve data redundancy, functional redundancy and functional coordination. This can be realized primarily due to the advances in digital and communications technology within a substation, particularly the process bus which allows data sharing between Intelligent Electronic Devices(IEDs). Results of backup protection investigation, using redundant information both within the substation and on a wide area basis, are then presented. A campus microgrid protection scheme was used as a test case to demonstrate the concept of protection using shared information. Finally, the paper proposes a multi-agent system as a simulation platform, which can be used to further demonstrate some of these concepts.