Overcurrent protection for distribution feeders with renewable generation

Distance protection is not utilized in distribution networks, unlike the transmission systems, due to the inherent characteristic of the distribution networks and the additional required facilities of distance protection, compared with over-current protection, which is in use in the distribution systems. This paper discusses the measured impedance by six elements of distance relay first zone applied on a distribution feeder in the case of a single phase to ground (AG) fault. This is done by presenting the measured impedance at the source node the distance relay ideal tripping characteristic for each element. The variation of the ideal tripping characteristic due to the changes in the system parameters is investigated.

Directional overcurrent and earth-fault protections for a biomass microgrid system in Malaysia

Due to its easy installation, easy operation and plenty solar light, the photovoltaic (PV) generators were the ones that emerged as favourites among the other types. However, the high integration of PV generators in distribution networks may cause impacts on power system protection, mainly on overcurrent protection (OCP). This work aims to assess the variation of fault currents magnitude through the OCP relays of a distribution network with integration of small scale PV generators. The distribution feeder and the PV generator were implemented in Simulink <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> /MATLAB <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> and the faults were applied at two different points. As the fault moves away from substation, the positive variation of the fault current through OCP relay increases and the negative variation decreases. Moreover, the current variability for line-to-ground (LG) faults are, in average, 130.94% greater than three line-to-ground (3LG) faults. In the case where the fault is upstream from OCP relay, the average current variation was -1,443.22% for 3LG faults and -842.28% for LG faults. This can lead to miscoordination and tripping issues of OCP devices, making it necessary to evaluate the impacts on protection system reliability.

This paper presents a design of non-directional overcurrent relay micro-controller-based having the advantages of low cost, high performance and can be totally manufactured by local manufacturers. The proposed overcurrent relay can be employed to protect feeders of distribution systems for overcurrent and earth fault protection. Also, the proposed relay is considered a high speed overcurrent relay, thus it can be used for restricted earth fault applications. The main hardware platform is designed and tested with pickup accuracy not more than 0.001In and total scan cycle not more than 1ms which make this relay very accurate and adequate for fast tripping applications. . The relay has the capability to treat the incoming analogue signals of voltages and currents via the Discrete Fourier Transform (DFT) through the designed main hardware platform. In this way if the relay protects a distribution power transformer, it can detect the inrush conditions via the second harmonic detection. Also it can detect the over excitation via the fifth harmonic calculations to block the abnormal tripping for more reliable and secure distribution systems.

Protection system in a power system domain plays a vital role as watchmen to safe guard power system apparatus in the event of faults. The integrity and effectiveness of these watchmen is heavily dependent on the reliability of the components that makes up the system. One of the main components in a protection system is protective relays that provides decision making element for correct protection and fault clearing operations. Failure of the protection devices may reduce the reliability of the power system protection that will impact the overall performance of the power system. Hence it is imperative for power utilities, such as Tenaga Nasional Berhad (TNB) to assess the reliability of protective relays to assure it will perform its intended function without failure. This paper will discuss the application of reliability block diagram (RBD) to assess the reliability and availability of a typical 132kV transmission overhead line protection system using historical failure data of protective relays.

Distance protection is not utilized in distribution networks, unlike the transmission systems, due to the inherent characteristic of the distribution networks and the additional required facilities of the distance protection, compared with over-current protection, which is in use in the distribution systems. This paper studies the measured impedance at the source node of a distribution feeder with dispersed generation (DG) unit. The ideal tripping characteristic is presented for the distribution feeder with DG unit. The variation of this tripping characteristic is investigated as a function of DG unit parameters. The especial case of the absence of the fault resistance is highlighted.

This paper introduces a technique for assessing the reliability of protection and control systems using reliability models and event tree analysis. This technique allows a quantitative reliability assessment to be made, which can then be used to determine the effect of integrating different protection and control functions into a single unit. The term reliability when applied to protection system failure can be considered in terms of dependability and security. Dependability is defined as the probability that the protection operates satisfactorily when required, i.e. it does not fail to trip. Security is defined as the probability that the protection does not operate when not required to do so, i.e. it does not produce unwanted trips. Dependability results are given in this paper for feeder protection schemes based on differential protection, distance protection and combined differential and distance protection. The effect on the dependability of these schemes of including a separate and an integral intertrip unit is also considered. The former is housed in its own hardware, and the latter is integrated into the differential protection. Both intertrip units can be activated by either protection.

The protection system in electrical engineering is a crucial component in maintaining electrical reliability. The protection system is a vital component that needs attention. Its utility not only serves as a parameter for the reliability of the electrical system but also as a safeguard for electrical system devices, starting from power suppliers (Power Plants), interconnection networks, transmission networks, to distribution networks. In Indonesia, with the unique dynamics of the domestic market, periodic evaluation of relays becomes important. This study investigates the current status and dominance of relay usage in Indonesia. Using a literature study method, we broadly identify the functions, utilities, and applications of Over Current Relay (OCR), Ground Fault Relay (GFR), Differential Relay, and Reverse Power Relay in Indonesia's electrical system. This literature study outlines several types of relays in Indonesia and their dominant usage in the electrical system, providing insights for readers and institutions using relays in Indonesia's electrical system. The implications of this literature study are to broaden the knowledge of the authors and readers and to encourage continuous innovation. With an understanding of the types of relays in Indonesia's electrical system, strategic steps can be taken to improve the reliability and efficiency of the electrical protection system in Indonesia.

This paper focuses on studying a complete comparison between analog and digital overcurrent relays. Analog term is given to the first generation of the electromechanical relays whereas digital term is associated with the up-to-dated relays. Digital relays are presently used for secured, dependable and efficient operation of power systems. In power systems, overcurrent protection is essentially required against short circuit faults. The parameters of overcurrent relays are critical and sensitive as incorrect settings of them can cause improper tripping leading to a big problem. Accordingly, these parameters must be tested in order to validate the relay performance subjected to different fault cases. Thus, a radial power system with different fault conditions is taken as a case study using both analog and digital relays individually. The whole proposed system is designed, implemented and simulated using MATLAB program software. The most suitable overcurrent relay adequate with radial power systems is based on time definite characteristics. The overall model is then simulated twice to analyze, study and differentiate the performance of both digital and analog relays when subjected to short circuit faults. Finally, A brief comparison is presented between the analog and digital overcurrent relays showing the features and benefits of digital overcurrent relays over the analog relays.

The transformation of passive distribution systems to more active ones thanks to the increased penetration of distributed energy resources, such as dispersed generators, flexible demand, distributed storage, and electric vehicles, creates the necessity of an enhanced test system for distribution systems planning and operation studies. The value of the proposed test system, is that it provides an appropriate and comprehensive benchmark for future researches concerning distribution systems. The proposed test system is developed by modifying and updating the well-known 33 bus distribution system from Baran & Wu. It comprises both forms of balanced and unbalanced three-phase power systems, including new details on the integration of distributed and renewable generation units, reactive power compensation assets, reconfiguration infrastructures and appropriate datasets of load and renewable generation profiles for different case studies.

This paper presents a scheme of distance protection for a renewable energy plant in electric power distribution systems. In many developing countries where renewable energy power plants are typically located in rural remote areas, they must be connected to weak power distribution systems inevitably. Although over-current relays are used to protect feeders at substations, fuses are only available elsewhere along feeder lines. To secure the system operation, distance protection is assigned to protect feeders. In this paper, distance relays are placed in the feeder along with over-current relays and fuses. Design of the distance protection of multi-source systems is described. This study considered the system consisting of a renewable energy plant. The power plant was a 6-MW unit of firmed power generation. The test feeder was simplified to be an equivalent four-bus test feeder for relaying purpose. Fault analysis in this paper was performed by using PowerWorld™ software. Obtained fault currents were used to establish protective zones of distance relays. In addition, this paper also compared the result of using distance protection with those of using directional over-current protection. As a result, protection of the power feeder with renewable power plants by using distance relaying can reduce complication in relay setting due to the impedance-based setting of the distance relay.

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

Design of enhanced energy meter using GSM prepaid system and protective relays

Toward sustainable microgrids with blockchain technology-based peer-to-peer energy trading mechanism: A fuzzy meta-heuristic approach

Because the intelligent substation is composed of a variety of intelligent electronic components, various types of information data will be generated during its operation. With the continuous implementation and rapid development of smart grid construction, the application of smart substations in power systems is becoming more and more extensive, and the number and scope of use are gradually expanding. In the face of the substantial increase in the commissioning of smart substations, people are paying more attention to the reliability of relay protection devices in smart substations during use. Strengthening research on the relay protection system of intelligent substations and improving the reliability of the system are urgent problems that need to be solved. The digitization of data information of the whole station is a typical feature of intelligent substations, on this basis, distributed relay protection can be realized; At the same time, the system-level status information can be identified and evaluated. Because there are too many spatial states, the calculation is very complicated. To solve this problem, this paper proposes to calculate the reliability of the relay protection device by Markov method, and then calculate in system level by GO method. Combining the Markov algorithm model with the GO method, the reliability of the relay protection system is calculated and analyzed, enabling the on-site operation and maintenance personnel to grasp the basic status of the relay protection device and the system operation in real time, obtain real-time feedback information, and better relay protection work of smart substations.