• 방재기술
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• 통권11호
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• pp.13-22
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• 1991

To understand electrical fire, the cause of it is classified into overcurrent, short circuit, leak, joint, overheat, accumulation of heat, spark, deterioration of insulation, static electricity, and lightning etc. and explained. And then by the precautions to it, proposed to the improvement of electric products, the completeness of safecty management and the use of alarm systems.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1043-1051
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• 2018

The coordination of directional overcurrent relay (DOCR) is employed in this work, considering gray wolf optimizer (GWO), a recently designed optimizer that employs the hunting and leadership attitude of gray wolves for searching a global optimum. In power system protection coordination problem, the objective function to be optimized is the sum of operating time of all the main relays. The coordination of directional overcurrent relays is formulated as a linear programming problem. The proposed optimization technique aims to minimize the time dial settings (TDS) of the relays. The calculation of the Time Dial Setting (TDS) setting of the relays is the core of the coordination study. In this article two case studies of IEEE 6-bus system and IEEE 30-bus system are utilized to see the efficiency of this algorithm and the results had been compared with the other algorithms available in the reference and it was observed that the proposed scheme is quite competent for dealing with such problems. From analyzing the obtained results, it has been found that the GWO approach provides the most globally optimum solution at a faster convergence speed. GWO has achieved a lot of relaxation due to its easy implementation, modesty and robustness. MATLAB computer programming has been applied to see the effectiveness of this algorithm.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1590-1599
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• 2016

The installation of distributed generation (DG) in the electrical networks has numerous advantages. However, connecting and disconnecting of DGs (CADD) leads to some problems in coordination of protection devices due to the changes in the short circuit levels in the different points of network. In this paper, an adaptive method is proposed based on available setting groups (SG) of relays. Since the number of available SG is less than possible CADD states, a classifying index (CI) is defined to categorize the several states in restricted setting groups. Genetic algorithm (GA) with a suitable objective function (OF) is used as an optimization method for the classification. After grouping, a modified coordination method is applied to achieve optimal coordination for each group. The efficiency of the proposed technique is demonstrated by simulation results.

• 조명전기설비학회논문지
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• 제29권6호
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• pp.58-62
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• 2015

When an emergency generator is running, it supplies the power for critical loads. Generator protection requires the consideration of many abnormal conditions that may occur with generators include overvoltages and ground faults. Modern day power systems create harmonics within the electrical network that can have an impact upon the associated protective system. This paper focuses on the analysing of the cause and development of a solution for the malfunction of induction disc type overcurrent ground relay by generation of harmonics during emergency generator operation.

• Journal of Power Electronics
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• 제13권3호
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• pp.381-389
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• 2013

A method to control the speed or the torque of a permanent-magnet direct current motor is presented. The rotor speed and the external torque estimation are simultaneously provided by appropriate observers. The sensorless control scheme is based on current measurement and switching states of power devices. The observers performances are dependent on the accurate machine parameters knowledge. Sliding mode control approach was adopted for drive control, providing the suitable switching states to the chopper power devices. Despite the predictable chattering, a convenient first order switching function was considered enough to define the sliding surface and to correspond with the desired control specifications and drive performance. The experimental implementation was supported on a single dsPIC and the controller includes a logic overcurrent protection.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.612-620
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• 2017

Relay coordination in power system is a complex problem and so far, meta-heuristic algorithms and other methods as an alternative approach may not properly deal with large scale relay coordination due to their huge time consuming computation. In some cases the relay coordination could be unachievable. As the urgency for a proper approach is essential, in this paper an innovative and simple relay coordination method is introduced that is able to be applied on optimization algorithms for relay protection coordination. The objective function equation of operating time of relays are divided into two separate functions with less constraints. As the analytical results show here, this equivalent method has a remarkable speed with high accuracy to coordinate directional relays. Two distribution systems including directional overcurrent relays are studied in DigSILENT software and the collected data are examined in MATLAB. The relay settings of this method are compared with particle swarm optimization and genetic algorithm. The analytical results show the correctness of this mathematical and practical approach. This fast coordination method has a proper velocity of convergence with low iteration that can be used in large scale systems in practice and also to provide a feasible solution for protection coordination in smart grids as online or offline protection coordination.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.137-144
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• 2006

This paper proposes novel protection schemes for grid-connected distributed generation (DG) units using the fault location algorithm. The grid-connected DG would be influenced by abnormal distribution line conditions. Identification of the fault location for the distribution lines at the relaying point of DG helps solve the problems of the protection relays for DG. The proposed scheme first identifies fault locations using currents and voltages measured at DG and source impedance of distribution networks. Then the actual faulted feeder is identified, applying time-current characteristic curves (TCC) of overcurrent relay (OCR). The method considering the fault location and TCC of OCR might improve the performance of the conventional relays for DG. Test results show that the method prevents the superfluous operations of protection devices by discriminating the faulted feeder, whether it is a distribution line where DG is integrated or out of the line emanated from the substation to which the DGs are connected.

• 전자공학회논문지A
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• 제28A권1호
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• pp.8-14
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• 1991

A new algorithm for calculation of overcurrent and overvoltage at load for parallel two-wire transmission line with nonlinear protection circuits induced by and external electromagnetic pulse is suggested. The rigorous solution is obtained for a particular type of the incident waveform and protection circuit. The validity of our algorithm is checked by comparing numerical results to the analytic solution in the particular case.

• 전기학회논문지
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• 제59권10호
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• pp.1754-1760
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• 2010

The HVDC system consists of ac side and dc side through thyristor valve. ac side protection is similar to conventional ac system protection schemes but dc side protection is different from ac side of HVDC system. AC system don't have controller but HVDC system has controller that controls and protects system from faults and disturbance. This paper show protectional function of HVDC dc side such as asymmetry protection, ac/dc differential protection, dc overvoltage, dc overcurrent protection. Protection models is developed using RTDS software and assessment of protection models is also performed by RTDS system.

• 한국산학기술학회논문지
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• 제21권3호
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• pp.129-136
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• 2020

컷아웃스위치(COS: Cut Out Switch 이하 COS)는 전력계통에서 수용가로 전력을 송배전하기 위해 사용되는 변압기의 입력단에 설치되어 사고전류로부터 변압기를 보호하기 위해 설치되는 보호장치이다. COS는 크게 퓨즈링크와 COS몸체 및 접속부로 구성되어 사고전류시 퓨즈링크의 엘리먼트가 용단되어 사고전류를 차단하는 역할을 한다. COS 퓨즈링크가 용단되어 발생하는 강력한 아크가 화염과 소음을 유발시켜 주변지역 거주자에게 불쾌감 및 공포감을 주며, 아크화염으로 인하여 주변기기의 2차 피해를 유발시킬 수 있다. 본 논문에서는 COS 동작 시 발생되는 아크와 소음 및 보호협조의 문제점을 해결하기 위해 폭발형이 아닌 한류형 COS 퓨즈를 개발하였다. 또한 과전류 차단 기능이 없는 한류형 퓨즈의 단점을 개선하기 위해 퓨즈 엘리멘트, 스트라이커와 COS 퓨즈금구 개발을 통하여 과전류 차단성능의 신뢰성을 향상시켰다. COS의 동작 특성 향상은 퓨즈 엘리멘트의 최적 형상 도출, 스트라이커의 원활한 동작을 위한 동작선의 재질과 두께 및 저항 산정, 그리고 스트라이커와 연계된 하부금구류의 구조 개선을 통하여 수행하였다. 본 연구에서 개발한 COS 퓨즈링크는 공인기관의 시험을 통하여 차단성능과 보호협조 성능을 검증하였다. 시험은 본 연구의 한류형 COS와 기존의 폭발형 비한류형 COS의 비교 시험으로 수행하였다.