지상변압기의 내부 보호장비 작동을 위한 MCA 보호협조에 대한 연구

현승윤,김창환,Hyun, Seung-Yoon,Kim, Chang-Hwan 한국전력공사 2022 KEPCO Journal on electric power and energy Vol.8 No.1

KEPCO's plan is undergoing a trial operation to replace the open-loop section with ring main units configuration where underground distribution lines are installed, by linking the multi-way circuit breakers auto (MCA) on the power side of each pad-mounted transformer. However, ring main units application mentioned above may cause the ripple effects, when implementing the configuration without a study of protection coordination. Because ring main units with classical pre-set protection devices contribution in fault condition didn't consider yet. For the reliable ring main units operation, it is necessary to resolve several protection issues such as the protection coordination with substation side, prevention of the transformer inrush current. These issues can radically deteriorate the distribution system reliability Hence, it is essential to design proper protection coordination to reduce these types of problems. This paper presents a scheme of ring main units' configuration and MCA's settings of time-current curves to preserve the performance of protection coordination among the switchgears considering constraints, e.g. prevention of the ripple effects (on the branch section when a transformer failure occurs and the mainline when a branch line failure occurs). It was confirmed that the propagation of the failure for each interrupter segment could be minimized by applying the proposed TCC and the interrupter settings for the MCAs (branch, transformer). Further, it was verified that the undetected area of the distribution automation system (DAS) could be supplemented by having the MCA configurated ring main units operate first, instead of the internal protection equipment in the transformer such as the fuse, STP when a transformer failure occurs.

Protection Coordination Using Superconducting Fault Current Limiters in Microgrids

Raza Haider,Muhammad Saeed Uz Zaman,Syed Basit Ali Bukhari,Zahoor Ahmed,Muhammad Mehdi,Yun-Sik Oh,Chul-Hwan Kim 한국조명·전기설비학회 2017 조명·전기설비학회논문지 Vol.31 No.10

Power generating units in the form of distributed generation (DG) are integrating with microgrid (MG) systems to supply reliable power to users. The trend of an integrated power supply is increasing continually to meet growing energy demands. Besides certain advantages of the MG system, some interconnection and system protection issues pose a challenge in terms of implementation. These problems need to be addressed in order to facilitate smooth operation of power systems. Superconducting fault current limiters (SFCLs) provide the best performance and unique protection features to electrical power systems during various fault conditions. This paper describes modeling, characterization, and implementation of SFCL in an MG system to enhance protection coordination. The proposed SFCL is modeled in MATLAB/ Simulink software and the performance of the system is validated through simulation results. It is also shown that the proposed SFCL provides a means of better relay coordination during various fault conditions. This is achieved by incorporating well-calculated design parameters of SFCL and its placement at optimal locations.

A Protection Ratio with Composite Fade Margin for Detailed Frequency Coordination in Microwave Relay System Network

Kyoung-Whoan Suh 한국전자파학회JEES 2007 Journal of Electromagnetic Engineering and Science Vol.7 No.2

In this paper, the formulation of the protection ratio based upon a composite fade margin and availability is newly presented for the detailed planning of frequency coordination in the microwave relay system network, and computed results for co-channel and adjacent channel protection ratios are illustrated over an actual system with 6.2 ㎓. It is shown that the protection ratio to assure a quality of service can be expressed in terms of the composite fade margin, noise-to-interference ratio, net filter discrimination, and system parameters. In addition, the net filter discrimination, depending upon the transmitter spectrum mask and the overall receiver filter characteristic, has been examined to investigate the effect of the adjacent channel protection ratio caused by the adjacent channel interference. Regarding simulated results for 6.2 ㎓, 60 km, 64-QAM, and N/I=6 ㏈ at the bit error rate of 10??, composite fade margin and co-channel protection ratio yield 25.14 and 50.3 ㏈, respectively. Also, the net filter discrimination of 26.5 ㏈ and the adjacent channel protection ratio of 23.8 ㏈ are obtained at the first adjacent channel of 30 ㎒. The proposed method provides some merits in view of a comprehensive and practical application with more detailed and various system parameters needed to access the criteria for making the proper frequency coordination.

Adaptive Protection Algorithm for Overcurrent Relay in Distribution System with DG

Byung Chul Sung,Soo Hyoung Lee,Jung-Wook Park,A. P. S. Meliopoulos 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.5

This paper proposes the new adaptive protection algorithm for inverse-time overcurrent relays (OCRs) to ensure their proper operating time and protective coordination. The application of the proposed algorithm requires digital protection relays with microcontroller and memory. The operating parameters of digital OCRs are adjusted based on the available data whenever system conditions (system with distributed generation (DG)) vary. Moreover, it can reduce the calculation time required to determine the operating parameters for achieving its purpose. To verify its effectiveness, several case studies are performed in time-domain simulation. The results show that the proposed adaptive protection algorithm can keep the proper operating time and provide the protective coordination time interval with fast response.

Adaptive Protection Algorithm for Overcurrent Relay in Distribution System with DG

Sung, Byung Chul,Lee, Soo Hyoung,Park, Jung-Wook,Meliopoulos, A.P.S. The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.5

This paper proposes the new adaptive protection algorithm for inverse-time overcurrent relays (OCRs) to ensure their proper operating time and protective coordination. The application of the proposed algorithm requires digital protection relays with microcontroller and memory. The operating parameters of digital OCRs are adjusted based on the available data whenever system conditions (system with distributed generation (DG)) vary. Moreover, it can reduce the calculation time required to determine the operating parameters for achieving its purpose. To verify its effectiveness, several case studies are performed in time-domain simulation. The results show that the proposed adaptive protection algorithm can keep the proper operating time and provide the protective coordination time interval with fast response.

협조된 SPD시스템에서 접속선의 길이가 에너지협조에 미치는 영향

이복희(Bok-Hee Lee),신희경(Hee-Kyung Shin) 한국조명·전기설비학회 2014 조명·전기설비학회논문지 Vol.28 No.6

For the purpose of designing and applying the optimum surge protection scheme, multi-stage coordinated surge protective device(SPD) system is suitable to successfully fulfill its tasks; first, to divert a large amount of the transient energy, second, to clamp the overvoltage to the level below the withstand impulse voltage of the equipment to be protected. The length of SPD connecting leads shall be as short as possible. Long connecting leads will degrade the protection effect of SPDs. In this paper, the influences of the length of connecting leads on the energy sharing in a coordinated SPD system were investigated experimentally, and the simulation of determining the energy sharing and protection voltage level of each SPD depending on the length of connecting leads was carried out by using P-spice program. It was confirmed that the protection voltage level and energy sharing in coordinated SPD systems are strongly influenced by the length of connecting leads.

직류배전망의 한류기를 고려한 보호협조 대책 개발

권기현 한국조명.전기설비학회 2022 조명·전기설비학회논문지 Vol.36 No.7

Recently, DC distribution system is being considered as one way to achieve the net zero to reduce the carbon emissions. However, there are still challenges to be overcame in order to introduce the DC distribution system, and in especially, it is necessary to develop a protective method considering the protective coordination for the stable and safe operation in DC distribution system. According to the analysis result of the fault current characteristics in DC distribution system, the fault should be detected before the fault current flows into the anti-parallel diodes in AC/DC converter. In this study, the Inverse Over-Current Relaying (IOCR) method is used to achieve the protective coordination. Since the fault detection by IOCR can be delayed according to the fault current, this paper proposes the use of Fault Current Limiter (FCL) to prevent the damage to the anti-parallel diodes. Overall, the protective method is developed so that the IOCR can operate even when the fault current is reduced due to the FCL. To verify the proposed method, a test system is modeled using Electro-Magnetic Transients Program (EMTP) and the simulation results for the several cases are analyzed.

Optimal Placement of Automatic Switching Equipment in Radial Distribution Networks Based on Protective Coordination

Masoud Amohadi,Mahmud Fotuhi-Firuzabad 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.3

Automatic switching equipment and protection devices (AS/PDs) play a fundamental role in radial power distribution networks. In this paper, a new hybrid method is presented to determine the optimal number, types, and locations of AS/PDs based on protective coordination. When a short circuit fault occurs in a medium voltage distribution network (MV feeder), AS/PDs such as relays, fuses, auto-reclosers and sectionalizers can be employed to disconnect the faulty part from the healthy area. The use of automatic switches at proper locations can signifi cantly decrease system interruptions. The costs of investment, maintenance, and unsupplied energy are considered in the cost function. This function must be minimized in order to obtain the optimal automatic switches, using particle swarm optimization. Furthermore, ant colony optimization is utilized to specify the main branch of MV feeder. The protection equipment determined in this branch is coordinated to protect the feeder against probable faults. If coordination of PDs is not achieved completely, the sizes and locations of AS/ PDs are recalculated. The proposed technique is implemented on a feeder of Isfahan power distribution network, as a sample feeder. The obtained results indicate that the proposed technique is acceptable and effi cient.

스팀터빈 발전기 비동기 투입 사례연구를 통한 비동기 방지 알고리즘 개발

이종훤(Jong-Hweon LEE) 대한전기학회 2012 전기학회논문지 Vol.61 No.10

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator"s amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. When calculation method of protection settings and logic for protection of generator asynchronization will be recommended, a distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection, this paper describes an improved backup protection coordination scheme using a new logic that will be suggested.

Protective Coordination of the OCR with the Voltage Component in a Closed-Loop Power Distribution System with the FCL

Seung-Taek Lim,Sung-Hun Lim 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.6

Recently, the requirement of the electrical energy from the renewable source has been growing in the South Korea since government’s energy plan to generate the electrical power of 20% as renewable source. In addition, these renewable power plants have been constructed on not only the existing power plant’s side but also customer’s side. These changes in power distribution system cause the fault current to increase higher and to reverse the direction of the fault current. Variable countermeasures to reduce the fault current have been studied and the introduction of the superconducting fault current limiter (SFCL) in the power distribution system, one of them, has been actively reported. However, the installation of the SFCL can aff ect the power system protection because of the fault current’s decrease or increase, which depends on the construction of the power distribution system. Especially, the application of the SFCL in a closed-loop power distribution system can cause the delayed trip operation or the fast trip operation of the over-current relay (OCR), one of the representative protective devices widely used in a power distribution system. This change can infl uence on the existed protective coordination. In this paper, the OCR with voltage component, one of the methods to suppress its trip operation’s change in a power distribution system with a closed loop construction due to the application of the SFCL, was suggested and the protection coordination between the OCRs in a power distribution system with a closed loop was analyzed. It was confi rmed that a simple using voltage component in the OCR could cause the trip variation of the reverse direction OCR in loop power system and it can be improved by matching the relaying voltage components.