Existing Protection Coordination Research Articles

Selection of TCC Curve and Protection Cooperation Method of Distribution Line Using Linear Optimization

Distribution systems are mostly composed of radial structures, which are susceptible to an increased variability and complexity of system operation due to frequent line changes during operation. When multiple changes in distribution lines occur simultaneously, the relative positions of protective devices also change. The existing protection coordination method of distribution lines is configured by considering the operation characteristics and coordination time interval (CTI) of all protective devices in series from the substation to the terminal load. Therefore, the protection coordination algorithm needs to be redesigned whenever a line is changed or a protective device is added to the distribution line for which the existing protection coordination algorithm has been set. In addition, existing protection coordination methods require complex calculations and procedures, which are subject to human errors and are less feasible for responding in real-time to changes in the distribution system. In this paper, we propose the adaptive time–current curve (TCC) method by selecting the time dial setting (TDS) and minimum response time (MRT) of individual protective devices in accordance with the relative distance based on the linear optimization technique. Using PSCAD/EMTDC, a power system analysis program, the minimum operating current and the fault current of each protective device are obtained, and the proposed protection coordination algorithm is verified according to the series configuration relationship of the protective devices. Finally, the proposed method is applied to an actual distribution line to verify the improvement over the existing protection coordination.

LSTM-Based Fault Direction Estimation and Protection Coordination for Networked Distribution System

While the world’s power distribution system resembles an intricate web-like structure, the most conventionally implemented distribution mechanism is the radial distribution system (RDS) where connection points for each distribution line are normally kept open. However, disadvantages regarding the traditional system have led to active research on establishing the networked distribution system (NDS), in which multiple circuits are interconnected with electricity as well as high-speed communication systems. The NDS offers multiple advantages including increased facility utilization, increased hosting capacity, and higher terminal voltage. Conversely, an unsolved issue prevails as the existing protection coordination method designed for the RDS is inadequate for fault occurrences in the NDS due to inaccurate fault direction identification. Hence, there is an urgent need for an alternative protection coordination method that allows high precision fault direction identification through communication. Moreover, the application of various existing technologies is hindered as the distance relay protection coordination algorithm malfunctions in situations where distribution lines are of short length, loads are dispersed onto multiple lines, and integration of distributed generation (DG) is frequent. Therefore, this paper presents a fault direction identification method that uses the waveform of the fault current based on long short-term memory (LSTM) neural network and a communication-based protection coordination scheme that can be applied in fault situations within an NDS.

Impact of distributed power generation on protection coordination in distribution network

<p>In the whole world and especially in Morocco, the electric power sector faces significant challenges and the demand for energy is increasing as fossil fuel sources are disappearing. Moreover, the high cost of construction of large production plants and the obligation to reduce greenhouse gas emissions are among the factors pushing the energy sector to integrate distributed generators DGs based on renewable energies into power grids. However, the integration of these generators increased the values of short-circuit currents in the network, which poses a real threat to the existing protection coordination systems in the distribution network. The aim of this article is to bring together in a single platform all available research addressing the issue of protection coordination in the presence of DGs in the distribution network, in order to help researchers identify future scope. This paper presents a review of the impact of distributed generators on the protection coordination of distribution networks. The solutions proposed in the literature, to mitigate the negative impact of DGs, have been investigated in detail, along with the limitations of these proposed techniques.</p>

Investigating the impact of protection system reinforcement cost on the consumers associated with renewable integrated distribution network

Conventional distribution network is a radial network with a single power source. Usually, overcurrent protection schemes are employed for such system protection for their simplicity and low cost. With the introduction of renewable generations, the existing protection coordination needs to be upgraded. Provision of directional feature and the requirement of high capacity circuit-breakers at certain points for the protection scheme demands considerable investment. The renovation cost required for upgrading the protection scheme will significantly impact the network cost requirement and consequently distribution use of system (DUoS) charges. This study aims to investigate the impact of renewable generations on the DUoS charges considering the cost associated in revamping the protection scheme. A power flow based MW + MVAr-miles DUoS charging method, that considers used capacity of the network, is proposed to carry out the DUoS charging calculations. The proposed charging mechanism appraise/penalise the users in accordance they are affecting system power factor. Accordingly, the proposed pricing algorithm may encourage users to act based on the economic signal generated at each location. The proposed charging algorithm has been tested on IEEE-33 and IEEE-69 bus distribution systems to examine the impact of renewable generations on the use of network costs.

Fault Transient Analysis and Protection Performance Evaluation within a Large-scale PV Power Plant

In this paper, a short-circuit test within a large-scale PV power plant with a total capacity of 850MWp is discussed. The fault currents supplied by the PV generation units are presented and analysed. According to the fault behaviour, the existing protection coordination principles with the plant are considered and their performances are evaluated. Moreover, these protections are examined in simulation platform under different operating situations. A simple measure with communication system is proposed to deal with the foreseeable problem about the current protection scheme in the PV power plant.

A feasibility study of full-bridge type superconducting fault current controller on electric machine power stability

Recently, because of the advent of Smart Grid and integration of distributed generations, electrical power grids are facing uncountable challenges. Increase of fault current is one of such serious challenges and there are some fault current limiters (FCLs) that can limit the fault current. Existing grid protection FCLs, however, simply limit the fault current passively and can allow the existing protection coordination schemes to fail. This phenomenon leads to catastrophic failure in the complex system and may cause unpredictable power grid operation. Unlike a FCL, a superconducting fault current controller (SFCC) employs a full-bridge thyristor rectifier, a high temperature superconducting (HTS) DC reactor, and an embedded control unit to maintain the fault current level at a proper value by adjusting the phase angle of thyristors. This paper contains experimental and numerical analysis to design and fabricate a SFCC system for protection and stability improvement in power grids. At first, fundamental characteristics of a SFCC system were introduced. System circuit diagram and operational principles were proposed. Secondly, the developed small-scale SFCC system was introduced and verified. A 40 Vrms/30 Arms class prototype SFCC employing HTS DC reactor was fabricated and short circuit tests that simulate various fault conditions were implemented to verify the control performance of the fault current. Finally, the practical feasibility of application of the SFCC system to the power system was studied. The problems caused by three-phase faults from the power grid were surveyed and transient stability analysis of the power system was conducted by simulations. From the experimental and simulation results, we can verify the feasibility of the SFCC in power system.

A Novel and Smart Design of Superconducting Fault Current Controller: Implementation and Verification for Various Fault Condition

By the advent of the Smart Grid and integration of distributed generators, electrical networks are facing uncountable challenges. The existing protection schemes that simply limit the fault current to the predetermined set values may not perform optimally, and even the existing protection coordination schemes fail and lead to catastrophic failures in the increasingly complex and unpredictable grid operation. This paper proposes a novel and smart design of fault current controller constituting a full-bridge thyristor rectifier embedding a superconducting coil. When a fault occurs and the resulting current through the superconducting coil exceeds a certain preset value based on the current operating conditions of the grid to maintain the grid integrity, the magnitude of the fault current is regulated to a desired value by automatic controlling of the thyristor. This research also implements a lab-scale Smart FCC with smart current control capability and demonstrates the desired functionality and efficacy of design by changing the fault conditions. This proposed Smart FCC design will make the Smart Power Grid capable of self-healing against current faults.

Protection System Adjustment for High Penetration of Distributed Generation

Excessive number and capacity of Distributed Generation (DG) may cause problems to distribution systems. To maintain existing protection coordination, the system can generally allow DG to be connected at a limited capacity. In case of more DGs are to be connected, it is a challenging issue for distribution system engineers to conduct protection adjustment for which the system can allow increased level of DG penetration. This paper proposes three methods, concerning protection system adjustment, to allow high DG penetration, consisting of over-current protection resetting, directional recloser application, and fuse replacement with recloser. The rst method will help relieve the system constraint from existing pick-up current settings whereas the second one helps solve the problem of mis-operation of the mid-line recloser caused by DG back feed fault current. The nal method will be used to maintain fuse saving scheme. In this paper, the developed methods are simulated with a test system to illustrate their eectiveness on allowing higher penetration of DG to the system.

배전계통의 보호협조측면에서 본 분산전원 연계용량 검토

정부의 신ㆍ재생 에너지 관련 정책으로 인해 앞으로 국내에서 신ㆍ재생에너지원은 보급은 증가할 것으로 예상된다. 신ㆍ재생에너지원은 전원의 특성상 전력계통에 연계되어 운전하는 것이 일반적이지만 이러한 연계 운전은 전력 계통 계획 및 운영상에 상당한 영향을 미치게 된다. 기존 배전계동의 전력조류는 변전소에서 수용가를 향한 단방향이며 이를 기반으로 계통운영이 이루어지고 있으나, 신ㆍ재생에너지원의 연계로 배전계통에 양방향의 전력조류가 형성되므로 기존의 보호시스템의 신뢰성 및 전력품질이 저하될 수 있다. 따라서 신ㆍ재생에너지원의 연계평가에 대한 기술적 평가절차가 필요하다. 본 논문에서는 국내 배전계통의 전형적인 보호기기인 자동 재폐로 차단기와 구분 개폐기의 특성을 살펴보고, 현재의 자동재폐로 차단기-구분개폐기 보호시스템에서 분산전원의 연계용량을 검토하는 방안을 제시하고자 한다.

Study on Distribution Reliability with Parallel and On-site Distributed Generation Considering Protection Miscoordination and Tie Line

In distribution system, Distributed Generation (DG) is expected to improve the system reliability as its backup generation. However, DG contribution in fault current may cause the loss of the existing protection coordination, e.g. recloser-fuse coordination and breaker-breaker coordination. This problem can drastically deteriorate the system reliability, and it is more serious and complicated when there are several DG sources in the system. Hence, the above conflict in reliability aspect unavoidably needs a detailed investigation before the installation or enhancement of DG is done. The model of composite DG fault current is proposed to find the threshold beyond which existing protection coordination is lost. Cases of protection miscoordination are described, together with their consequences. Since a distribution system may be tied with another system, the issues of tie line and on-site DG are integrated into this study. Reliability indices are evaluated and compared in the distribution reliability test system RBTS Bus 2.