• 전기학회논문지P
• /
• 제58권1호
• /
• pp.90-94
• /
• 2009

The inundation of substation and ground power equipment breaks out every summer season in low-lying downtown and low-lying shore by localized heavy rain, typhoon and tidal wave. For diminishing flood damage of electrical equipment in the root, flood protection system which is used the basic frame of Pad transformer is developed using pneumatic pressure. This system is established on pressure generator equipment and sensor of flooded level operates at flooding occurrence and is maintained a shutting tightly structure. The system is able to protect indraft water in Pad Transformer and supply the electricity at emergency(flooding). And we tested safety for insulation resistance at flooding and applying an electrical current. We estimate that loss cost which is caused by with flooding and the power failure will be diminished if it is addition to advances the reliability evaluation by setting an example.

• 전기학회논문지
• /
• 제60권1호
• /
• pp.8-13
• /
• 2011

A percentage current differential relay is widely used for transformer protection. Because many percentage current differential relays recently use modified methods instead of conventional methods for deciding the operating characteristics of the large current region, in this paper, the operating region of a percentage current differential relay is analyzed in input-output current domain instead of operating-restraint current domain. An effective method to set the operating region when a CT is saturated is proposed with a series of investigations comparing a conventional method with the proposed modified method. The performance of the proposed method is evaluated for internal and external faults of a power transformer having the voltage rating of 345/154kV. EMTP-RV is used for the relaying data collection.

• 한국산학기술학회논문지
• /
• 제18권7호
• /
• pp.394-399
• /
• 2017

본 국내 교류전철변전소에서는 주변압기 2차측의 위상각이 $90^{\circ}$인 단상 전원을 얻도록 한 스코트 결선 변압기를 설치 운용 하고 있다. 변압기 보호계전기는 내부에서 고장이 발생하는 경우 변압기 전단에서 전력을 차단시키고 변압기 외부 계통의 사고나 일반차량 운행의 경우에는 동작하지 않아야 한다. 정확한 고장의 판단으로 오동작을 줄이는 것이 전력계통을 안정적으로 유지하고 신뢰성을 향상시키는 측면에서 매우 중요하다. 주 변압기 내부 고장 검출장치로는 브흐홀쯔계전기와 비율차동계전기를 설치하여 변압기를 보호하고 있지만 비율차동계전기의 오동작으로 인해 보호기능을 비활성화 시켜놓은 상태로 운용하는 사례가 있다. 본 논문에서는 스코트 변압기의 특성과 비율차동계전기의 특성을 제시하고 보호계전기의 오동작 사례를 분석하였다. 이를 위해 전력계통 해석프로그램을 이용하여 스코트 변압기에 사용되는 비율차동계전기를 모델링하고 A변전소의 Comtrade 파일로 저장된 고장파형을 입력데이터로 사용하여 동작여부를 판단하여 고조파 분석을 수행하였다. 또한, 고장파형 분석을 통해 오동작 사례에 대한 개선 방안을 도출하고자 한다.

• 방재기술
• /
• 통권7호
• /
• pp.32-37
• /
• 1990

• 전기학회논문지
• /
• 제56권11호
• /
• pp.1873-1878
• /
• 2007

Current differential relays may maloperate during magnetic inrush and over-excitation because a significant differential current is produced. To prevent maloperation, the relays adopt some harmonic components included in the differential current. The harmonic restraints may increase the security of a relay but cause the operating time delay of a relay when an internal fault occurs. Moreover, the operating time delay is more increased if a current transformer (CT) is saturated. This paper describes a current differential relaying algorithm for power transformer protection with a compensating algorithm for the secondary current of a CT. The comparative study was conducted with and without the compensating algorithm. The performance of the proposed algorithm was investigated when the measurement CT (C400) and the protection CT (C400) are used. The proposed algorithm can compensate the distorted current of a CT and thus reduce the operating time delay of the relay significantly for an internal fault with CT saturation.

• 전기학회논문지P
• /
• 제55권1호
• /
• pp.6-12
• /
• 2006

A popular method used by primary protection for power transformer is current ratio differential relaying (RDR) with 2nd harmonic restraints. In modern power transformer due to the use of low-loss amorphous material, the 2nd harmonic component during inrush is significantly reduced. The higher the capacitance of the high voltage status and underground distribution, the more the differential current includes the 2nd harmonic component during internal fault. Thus the conventional method may not operate properly. This paper proposes an advanced relaying algorithm and the prototype IED hardware design and it's real-time experimental results. To evaluate performance of the proposed algorithm, the study is well constructed power system model including power transformer utilizing the EMTP software and the testing is made through simulation of various cases. The proposed relaying that is well constructed using DSP chip and microprocessor etc. has been developed and the prototype IED has been verified through on-line testing. The results show that an advanced relaying based prototype IED never mis-operated and correctly identified all the faults and that inrushes that are applied.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2002년도 전력전자학술대회 논문집
• /
• pp.723-726
• /
• 2002

In this paper, a high efficiency leakage transformer for neon tube is developed to improve its power factor, to reduce its core loss and weight by using a technique of shape optimization and direction of grain-oriented silicon steel sheet. A protection circuit is designed for all types of neon transformer loaded with one or more neon lamps. Whenever the neon tube fails to be started up or comes to the life end, or encounters faults with open-circuits at the output terminals of the neon transformer, the protection circuit will be initiated to avoid more critical hazards. These neon transformers need a protection circuit to prevent from current stresses on circuit components by neon tube fail. The input of the transformer is automatically cut off when the abnormal condition occurs, preventing waste of no-load power. As the results of the study, the core weight is reduced by $11\%$, the power factor improved by $5\%$ and the efficiency increased by $6\%$ compared with the conventional type due to the employment of the grain-oriented steel sl)eel and the optimized core shape.

• 전기학회논문지P
• /
• 제52권4호
• /
• pp.179-188
• /
• 2003

Percentage differential characteristic scheme has been recognized as the principal basis for large transformer protection. Nowadays, relaying signals can contain second harmonic component to a large extent even in a normal state, and second harmonic ratio indicates a tendency of relative reduction because of the advancement of transformer's core material. And then, conventional second harmonic restraint differential relaying exposes some doubt in reliability. It is, therefore, necessary to develop a new algorithm for the effective and accurate discrimination. This paper deals with advanced fuzzy logic based relaying by using flux differential, and a new fault detection criterion logic scheme by using wavelet transform. To comparative analysis of proposed techniques, the paper constructs power system model including power transformer, utilizing the EMTP, and collects data through simulation of various internal faults and magnetizing inrush. The proposed fuzzy relaying and a new fault detection scheme were tested. The former, fuzzy relaying, was proven to be faster and more reliable than the latter.

• 조명전기설비학회논문지
• /
• 제19권4호
• /
• pp.85-90
• /
• 2005

매년 집중 호우 및 태풍${\cdot}$해일 등에 의해 도심 저지대 및 해안가 저지대의 수${\cdot}$변전설비 침수가 많이 발생을 하고 있다. 수${\cdot}$변전설비가 침수되면 전력 수급에 큰 문제를 발생시키고, 복구 시간이 많이 걸리기에 그에 따른 경제적 손실 발생과 침수된 설비에 의한 감전사고 발생 및 물적 피해가 발생을 한다. 따라서 이를 방지하기 위한 상습 침수지역에서의 수${\cdot}$변전설비 시설에 대한 시설 방안이 제시되어야 할 것이다. 이미 외국의 경우 전기설비의 중요성을 인식하여 침수지역에서의 전기설비 시설에 대하여 규정을 하고 있다. 본 논문은 국내에서 가장 많이 분포되어 있는 22.9[kV] 수${\cdot}$변전설비 시설 현황 및 침수방지 대책에 대한 현장실태조사를 하였고, 미국, 영국 등 국외 전기설비 침수방지 대책에 관한 규정들을 비교${\cdot}$분석하였다. 분석 결과 국내의 침수방지 대책이 현장 및 제도적으로 미비하였다. 따라서 본 논문은 현장실태조사 결과와 국외 침수방지대책에 관한 규정 분석을 토대로 상습침수지역에서의 수${\cdot}$변전설비 침수방지 대책을 제시하였다. 또한 본 연구 내용은 국내 관련 법 개정(안)을 제시하는데 근거 자료로 사용될 것이다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
• /
• pp.216-218
• /
• 2001

The transformer role is very important in power system operation and control; also its price is very expensive. Therefore many kinds of the efforts for transformer protection have been executed. So for as, current differential relay(87) has been mainly used for transformer protection. But current differential relaying method has several troubles as followings. Differential current can be occurred by transformers inrush current between winding1 and winding2 of transformer when transformer is initially energized. Also harmonic restrained element used in current differential relaying method is one of the causes of relays mal-operation because recently harmonics in power system gradually increase by power switching devices(SVC, FACTS, DSC, etc). Therefore many kinds of effort have been executed to solve the trouble of current differential relay and one of them is method using ratio of increment of flux linkages(RIFL) of the primary and secondary windings. This paper introduces a novel protective relay for power transformers using RIFL of the primary and secondary windings. Novel protective relay successfully discriminates between transformer internal faults and normal operation conditions including inrush and this paper includes real time test results using RTDS(Real Time Digital Simulator) for novel protective relay. A novel protective relay was designed using the TMS320C32 digital signal processor and consisted of DSP module. A/D converter module, DI/DO module, MMI interface module and LCD display module and developed by Xelpower co., Ltd.