• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.8
• /
• pp.1002-1008
• /
• 2018

Fault Ride Through(FRT) requirement prevents disconnections of distributed generations during the specific time on disturbance condition for system stability. However, since there is a limitation to the FRT capability of distributed generation, and the protection system needs to clear the fault quickly before the distributed generation is disconnected. Therefore, this paper proposes a novel optimal setting method of directional overcurrent relay considering FRT of distributed generation. The proposed method reduces the probability of disconnections of the distributed generation in disturbance without additional equipment considering the FRT capability of the distributed generation by calculating the optimal relay setting through the Genetic Algorithm(GA).

• Proceedings of the KIEE Conference
• /
• 1990.11a
• /
• pp.191-196
• /
• 1990

By the nature of distribution system, the coordination process of protection devices depends on various heuristic rules. This paper reviews the practical rules that adopted in coordination, and proposes some heuristic rules improving the coordination process.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.447-450
• /
• 1990

Nonlinear protection of overcurrent induced on parallel two-wire transmission line by electromagnetic pulse is analyzed. This algorithm is implemented numerically and simulation result for simple incident pulse and nonlinear type agrees with its analytic solution.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.8
• /
• pp.1163-1168
• /
• 2013

The maximum allowable value of loop impedance($Z_s$) to secure the operation of overcurrent protective devices and the safety for indirect contact is a very important in TN-C-S system. The loop impedance is divided into inner loop impedance which consumer can adjust and external loop impedance($Z_e$) which only electric operator can adjust. Thus, an external loop impedance which limits to less than a certain value is a very important factor for human body protection against electric shock in TN-C-S system. The concept of loop impedance($Z_s$) is recently introduced to the domestic, the study about external loop impedance is yet insufficient. However, the study about the reference impedance as specified by the IEC 60725 standard to improve the quality and reliability of the power supply is being made. In this paper, reference value of external loop impedance($Z_e$) to meet domestic environment will be proposed by the nationwide measurement and statistical analysis.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.3
• /
• pp.473-479
• /
• 2015

Thermal relays are sometimes used instead of long time overcurrent relays for motor protection. But, it is difficult for any relay design engineer to adequately approximate motor heating curves which represent the average of a difficult-to-define thermal zone. Thermal relays frequently may not provide sufficient protection on heavy overloads. Digital multifunction relays are microprocessor-based devices. These relays offer highly reliable and advanced protection of motors. If a situation can be mathematically described, the microprocessor in a digital relay can be programmed to tackle that problem. Today's motor protection is accomplished with digital protective relays. Digital relays offer additional, highly important features to complement protection. The best way to prevent short in motor is to not overheat and degrade the insulation.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.748-749
• /
• 2011

중앙 집중적이고 단방향 특성을 갖는 현재의 전력망에 대하여 신재생 에너지와 에너지 저장장치를 중심으로 하는 다양한 분산 전원의 도입에 따른 독립적 운영을 특징으로 하는 스마트 그리드로의 변화는 기존 전력망의 보호 동작에도 변화를 필요로 하게 된다. 이러한 분산전원의 연계와 스마트 그리드의 도입은 사고전류의 크기와 방향의 변화는 물론 양방향 계통에 의한 동작 변화가 발생하게 된다. 따라서 본 논문에서는 이러한 문제를 해결하기 위한 보호 알고리즘을 제시하였다. 배전계통에서 일반적으로 이용되는 과전류 계전기 (Overcurrent Relay, OCR)에 대하여 제안된 알고리즘의 적용을 통해 분산전원 도입을 비롯한 전력계통 상태 변화에 능동적으로 대응하여 보호협조가 유지될 수 있도록 하였다. 또한, 제시된 알고리즘의 성능 검증을 위하여 PSCAD/EMTDC를 이용한 시뮬레이션을 수행하였다.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.5
• /
• pp.854-859
• /
• 2007

A wind farm consists of many wind generator(WG)s therefore, it is generally a complex power system. A wind farm as a distributed generation(DG) affects utility power system. If a conventional protection schemes are applied, it is difficult to detect faults correctly and the schemes can't provide proper coordination in some cases. This paper presents a protection algorithm for a wind farm which consists of a looped collection circuit. Because the proposed algorithm can distinguish between an internal fault and an external fault in a wind farm, The proposed algorithm can disconnect the faulted section in a wind farm. This algorithm is based on an overcurrent protection technique with the change of the ratio of the output current of a generator to the current of the looped line connected to each generator to collect the each generator's power. In addition, operating time of the algorithm is shortened by using the voltage drop at a generator collection point. The performance of the proposed algorithm was verified under various fault conditions using PSCAD/EMTDC simulations.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.1
• /
• pp.43-49
• /
• 2011

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 this problem clearly, this paper describes an improved backup protection coordination scheme using an IEC 61850-based distance relay for transformer backup protection. IEC 61850-based IED(Intelligent Electronic Device) and the network system based on the kernel 2.6 LINUX are realized to verify the proposed method. And laboratory tests to estimate the communication time show that the proposed coordination method is reliable enough for the improved backup protection scheme.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.1229-1231
• /
• 2002

This paper presents the design of DC protection system of Light Rail Transit system. Especially, the composition and interface for DC Switchgear. Digital protection unit and sort of protection algorithm are focused. DC Switchgear (DCSWGR) for LRT testline consist of 5 different panels with peculiar characteristics are examined. Also Basic actuation principle for DC fault select relay (50F), Line Test Device (LTD), DC Overcurrent(OCR) relay are introduced.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.406-407
• /
• 2011

The closed-loop distribution system is more flexible and more reliable than radial system. If any type fault occurs, the reliability of system can be better by providing electrical energy through another distribution line. However, it needs protection device coordination of different type. Typically, it is available by using directional overcurrent relay (67). This paper gives a solution about loop protection relay modeling which can be used by the simulation tools.