Adaptive Overcurrent Protection Research Articles

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

Adaptive overcurrent protection against ferroresonance

Catastrophic equipment failures continue to occur today due to ferroresonance even though this phenomenon has been extensively studied over the past 90 years. Ferroresonance may also cause mal operation of some protective devices like overcurrent protection. Manitoba hydro network is analysed in PSCAD/EMTDC to recognise ferroresonance in case of line and plant outage. Impact of ferroresonance on mal operation of current-based protective relays is analysed. Then, an adaptive algorithm is designed in the relay to recognise ferroresonance and prevent mal operation of the relay.

LUT Assisted Adaptive Overcurrent Protection of Reconfigurable Microgrids

Microgrids are the key solution to handle the growing technical, environmental and economical concerns of existing power system networks. The purpose of this paper is to develop an intelligent and adaptive overcurrent protection system for a microgrid. This system is capable of monitoring, protecting and controlling the microgrid. A look up table is created and maintained at the central protection system of the microgrid, which has details of normal and faulted current in all feeders for various topologies of the microgrid system. It has the optimized values for time dial setting and operating time of relays for faults at a specific location in the reconfigured system, which is generated using Dual Simplex algorithm. Hence the Central Protection System aids in providing suitable overcurrent relay coordination to the microgrid, which may incur reduced network disconnection. The hardware prototype of the Central Protection System is realized, tested and validated on a balanced 21-bus microgrid system.

Comparison of Programmable Logic and Setting Group Methods for adaptive overcurrent protection in microgrids

Adaptive overcurrent protection systems for microgrids with distributed generators require that overcurrent relays need to be adjusted to different circuit paths and feeder fuses. Adaptive overcurrent protection systems in recent publications were based on the Setting Group method, using the functions resident in the relay. In this paper, the Programmable Logic method was developed for an adaptive overcurrent protection system, using the programmable logic and math operators instead of the functions resident in the relay. The Programmable Logic and Setting Group methods were validated using a real-time simulator with two relays in-the-loop. The selectivity, reliability and speed of the adaptive protection system based on the Programmable Logic and Setting Group (previous work) methods were compared for a microgrid with distributed generators (diesel generators). Similar results were obtained with both methods. However, the Setting Group method limited the number of overcurrent settings by the available setting groups of relays, and disabled the relays for a fixed amount of time, reducing the relay’s availability. On the other side, the Programmable Logic method is recommended because it improves the capacity of relays by using one setting group, and avoids relays to be disabled because switching setting groups is not being necessary. In microgrids that require an adaptive overcurrent protection system for different circuit paths and seasonal (winter and summer) settings, adaptive overcurrent protections based on programming alternative is a better solution. This requires relay engineers to be trained in relays’ programming techniques.

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.

Comparison of non-real-time and real-time simulators with relays in-the-loop for adaptive overcurrent protection

Non-real-time or real-time simulators with relays in-the-loop can be used to test and validate adaptive protection systems. In this paper, the non-real-time and real-time simulator test procedures with relays in-the-loop for an adaptive overcurrent protection system in a microgrid with distributed generators (diesel generators) were described, contrasting the test set-up and experiment preparation. In addition, test results for the non-real-time and real-time simulators with relays in-the-loop were compared. Selectivity, reliability and speed for an adaptive overcurrent protection system was validated using both relays in-the-loop test procedures. Of 44 tripping tests ran for both relays in-the loop techniques, the breakers near the fault tripped and the other breakers remained closed in 34 cases, and backup relays tripped when primary relays did not trip in 10 cases (backup tests). Inverse time overcurrent elements tripped breakers at maximum fault currents in less than 0.5s. To test adaptive overcurrent protection systems, it is recommended to use the relays in-the-loop with real-time simulator instead of non-real-time simulator, to optimize the test validation of primary and backup relays working together.

An Adaptive Overcurrent Protection Scheme for Distribution Networks

Distribution networks are evolving toward the vision of smart grids, with increasing penetration of distributed generation (DG), introduction of active network management (ANM), and potentially islanded modes of operation. These changes affect fault levels and fault current paths and have been demonstrated to compromise the correct operation of the overcurrent protection system. This paper presents an adaptive overcurrent protection system which automatically amends the protection settings of all overcurrent relays in response to the impact of DG, ANM, and islanding operation. The scheme has been developed using commercially available protection devices, employs IEC61850-based communications, and has been demonstrated and tested using a hardware-in-the-loop laboratory facility. A systematic comparison of the performance of the proposed adaptive scheme alongside that of a conventional overcurrent scheme is presented. This comparison quantifies the decrease in false operations and the reduction of mean operating time that the adaptive system offers.

Communication-based Adaptive Protection for Distribution Systems Penetrated with Distributed Generators

In this article, a communication-based adaptive over-current protection scheme for distribution systems penetrated with distributed generators is proposed. A communication network between the over-current relays, the distributed generators, and the utility grid is employed to automatically update the settings of the protective relays. Moreover, the communication reliability is increased through the addition of a backup communication system. The proposed scheme has the advantage of operating during grid-connected and islanding modes of operation. The scheme employs two simultaneous algorithms. The first algorithm works when the system configuration is changed due to the connection/disconnection of a distributed generator or the utility grid. The second algorithm efficiently uses the exchanged information between the relays to identify the faulted section and hence speeds up fault clearance. The proposed scheme is tested for difierent fault conditions as well as for different system configurations. The results demonstrated that relay operating times, including the communication delay, are greatly reduced when the faulted section is identified and relay settings are adjusted accordingly. In addition, a negligible time delay was experienced when the backup communication network was put in service.

An Adaptive overcurrent Protection Scheme for Distribution Networks Including DG Using Distribution Automation System and its Implementation on a Real Distribution Network

Recently, a great attention has been paid in applying Distributed Generation (DG) throughout electric distribution systems. Although DG has many advantages and benefits, it has to be applied after performing detailed investigations due to their complexities in operation, control and protection of network. One of the most considerable problems that arise, when DGs are used, is destructing efficiency and qualification of the existing protection system. The injected currents of DGs to a distribution network lead to not having a radial network anymore, and consequently network faces an inefficient protection system that was formerly designed according to the existing philosophy behind the distribution network. In this paper, a new protection scheme has been presented to provide the distribution networks including DGs. The new approach, designed based on capabilities of Distribution Automation System (DAS), has been implemented using a computer-based relay which is installed in the sub-transmission substation. The proposed scheme has been implemented on some part of a real distribution network in Shiraz which is a large city in Iran and performance of the proposed scheme is tested on it. For simulating the distribution network and for implementing the relay algorithm, DIgSILENT Power Factory 13.2 and MATLAB are used respectively.

An adaptive overcurrent protection scheme for distribution networks including DG using distribution automation system and its implementation on a real distribution network

An adaptive overcurrent protection scheme for distribution networks including DG using distribution automation system and its implementation on a real distribution network

A Simple Adaptive Overcurrent Protection of Distribution Systems With Distributed Generation

A significant increase in the penetration of distributed generation has resulted in a possibility of operating distribution systems with distributed generation in islanded mode. However, overcurrent protection of an islanded distribution system is still an issue due to the difference in fault current when the distribution system is connected to the grid and when it is islanded. This paper proposes the use of adaptive protection, using local information, to overcome the challenges of the overcurrent protection in distribution systems with distributed generation. The trip characteristics of the relays are updated by detecting operating states (grid connected or island) and the faulted section. The paper also proposes faulted section detection using time overcurrent characteristics of the protective relays. Simulation results show that the operating state and faulted section can be correctly identified and the protection system settings can be updated to clear the faults faster.

Adaptive Transformer Thermal Overload Protection

This paper is based on a report of the same title, prepared by Working Group K3 of the Substation Protection Subcommittee of the Power System Relaying Committee of the Power Engineering Society of the IEEE. The paper begins with background information on the causes, measurement techniques, and consequences of overheating in mineral-oil-immersed power transformers. Then techniques for adaptive transformer thermal overload protection based on the real-time solution of the transient heating equations are presented. An adaptive overcurrent protection implementation, and the related functional requirements, are discussed. The equations of Clause 7 of the 1995 IEEE Guide for Loading Mineral-Oil-Immersed Transformers are used in the analysis, with a slight modification to allow for continuously varying ambient temperature.

Adaptive transformer thermal overload protection

This paper is based on a report of the same title, prepared by Working Group K3 of the Substation Protection Subcommittee of the Power System Relaying Committee of the Power Engineering Society of the IEEE. The paper begins with background information on the causes, measurement techniques, and consequences of overheating in mineral-oil-immersed power transformers. Then techniques for adaptive transformer thermal overload protection based on the real-time solution of the transient heating equations are presented. An adaptive overcurrent protection implementation, and the related functional requirements, are discussed. The equations of Clause 7 of the 1995 IEEE Guide for Loading Mineral-Oil-Immersed Transformers are used in the analysis, with a slight modification to allow for continuously varying ambient temperature.