• 전기학회논문지P
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• 제61권4호
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• pp.174-179
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• 2012

The social and economic level of damages might be highly increased in the case of wide-area black-outages, because of heavy dependence of electricity. Therefore, the development of a wide-area protection relay intelligence techniques is required to prevent massive power outages and minimize the impact strength at failure. The frequency monitoring and prediction for wide-area protection relaying intelligence has been considered as an important technology. In this paper, a network-based frequency monitoring system developed for wide-area protection relay intelligence is presented. In addition, conventional techniques for frequency estimation are compared, and a method for advanced frequency estimation and measurement to improve the precision is proposed. Finally, an integrated monitoring system called K-FNET(Korea-Frequency Monitoring Network) is implemented based on the GPS and various energy monitoring cases are studied.

• 한국물환경학회지
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• 제28권3호
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• pp.473-478
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• 2012

To protect human health and manage increasing hazardous chemicals in stream area, it is necessary to expand water quality hazardous items based on risk assessment with proper monitoring data. Also, it is essential to set up the suitable monitoring frequency to produce reliable exposure data to derive water quality guidelines. However, there has been no harmonized monitoring frequency for risk assessment in both domestic and international monitoring systems. In addition, the monitoring frequency for risk assessment has been selected as 'Research needs' in the International Conference on Deriving Environmental Quality Standards for the Protection of Aquatic Ecosystems (EQSPAE) of 2011. In this study, Cases of UNEP/WHO, EU, European countries, USEPA, ANZECC/ARMCANZ, CCME, Japan, and Korea were analyzed to propose the monitoring frequency for risk assessment. Monitoring frequencies depending on environmental conditions, monitoring object, measurement parameters, and monitoring duration were extensively collected. We observed that a monthly monitoring has been applied at most of organizations including EU, USEPA, and UNEP/WHO. In this study, monitoring frequency of minimum 6 times during 3 years were proposed to conduct the risk assessment based on the current domestic status. However, it is necessary to make agreements among interested parties, and perform additional studies about optimal monitoring frequency to protect the aquatic ecosystem and human health in Korean rivers and streams.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.199-201
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• 2003

The monitoring effectiveness not only depends on the effectiveness of the network, but also the costs of the network. Generally the costs of the monitoring network are mainly on the equipment and personnel; the implementation and maintenance; the observation and sample connection; the sample analysis; and the data storage and processing. The cost of the monitoring network can be expressed as a function of monitoring frequency because the monitoring method can be an automatic or a manual measurement. To determine the sampling frequency of subsidiary groundwater monitoring stations, time series data of national groundwater monitoring stations were used. The proposed optimal sampling frequency for subsidiary groundwater monitoring station is about 7 to 20 days and the average frequency is about 2 weeks.

• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.776-785
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• 2011

Since the Internet-based real-time Global Positioning System(GPS) synchronized widearea power system frequency monitoring network (FNET) was proposed in 2001, it has been monitoring the power system frequency in interconnected United States power systems and numerous interesting behaviors have been observed, including frequency excursion propagation. We address the consistency of a frequency excursion detection order of frequency disturbance recorders in FNET in relation to the same generation trip, as well as the ability to recreate by power systems dynamic simulation. We also propose a new method, as an application of FNET measurement, to locate a tripped generator using power systems dynamic simulation and wide-area frequency measurement. The simulation database of all the possible trips of generators in the interconnected power systems is created using the off-line power systems dynamic simulation. When FNET detects a sudden drop in the monitoring frequency, which is most likely due to a generation trip in power systems, the proposed algorithm locates a tripped generator by finding the best matching case of the measured frequency excursion in the simulation database in terms of the frequency drop detection order and the time of monitoring points.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.215-220
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• 2012

In an earlier work, we proposed the chromatic dispersion monitoring technique of non-return to zero (NRZ) signal based on clock-frequency component (CFC) through numerical simulations. However, we have not yet shown any experimental demonstration or analytic derivation of it. In this paper, we show an experimental demonstration and analytic derivation of the proposed chromatic dispersion monitoring technique. We confirm that the experimental results and the analytic results correspond with the simulation results. We also demonstrate that monitoring range and accuracy can be improved by using a simple clock-extraction method.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.472-477
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• 2013

An internet-based, real-time GPS synchronized wide-area power system frequency monitoring network(FNET) has been monitoring wide-area power system frequency in continuous time in the United States. This paper analyzes the FNET measurement to the verified disturbances in the US eastern interconnected power system and simulates it using the dynamic system model. By comparing the frequency measurements with its simulation results to the same disturbances in detail, this paper finds that the sequence of monitoring points to detect the frequency fluctuation caused by the disturbances is matched well in the measured data and the simulation results. The similarity comparison index is also proposed to quantify the similarity of the compared cases. The dynamic model based simulation result is expected to compensate for the lack of FNET measurement in its applications.

• 한국터널지하공간학회 논문집
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• 제14권2호
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• pp.117-129
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• 2012

본 논문에서는 1995년 서울지하철 5, 7, 8호선 터널구조물에 국내 최초로 설치되어 운영 중에 있는 터널 유지관리 계측시스템에 대한 측정 및 분석주기를 국내 및 국외 적용사례와 국내 터널의 유지관리계측 분석결과 및 시설물안전관리 관계법령기준을 검토하여 향후에 적용할 터널 유지관리계측의 측정 및 분석주기를 설정하고자 연구를 수행하였다. 현재까지의 계측주기로 계측관리를 한 결과 계측주기에 따른 문제는 없는 것으로 판단되었다. 국내 지하철 5, 6호선 4개 터널의 유지관리계측 분석결과 콘크리트 라이닝 응력과 철근응력이 약 45개월 경과시점에서 서서히 수렴하는 것으로 분석되어 계측기 설치 후 약 4년 까지는 계측 측정 및 분석주기를 빈번하게 하고, 4년 이후에는 빈도를 늦추는 것이 타당할 것으로 판단된다.

• 전기학회논문지P
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• 제63권4호
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• pp.295-300
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• 2014

The frequency is an important operating parameter of a power system. There is an increasing importance of constant monitoring of frequency to achieve stable power supply by WAMS(wide area monitoring system) and FNET(Frequency Monitoring Network). This paper is part of development of a network-based frequency monitoring and failure prediction system for wide-area intelligent protection relaying. In this paper, analysis of propagation speed of power frequency by generation drop using the PSS/E was carried out. For dynamic analysis, the 11 metropolitan areas offices of KEPCO divided into five groups of Seoul, Gangwon, Chungcheong, Honam, and Yeongnam group, study was performed.

• Ocean and Polar Research
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• 제39권1호
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• pp.13-21
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• 2017

Temporal changes in the number of zooplankton species are important information for understanding basic characteristics and species diversity in marine ecosystems. The aim of the present study was to estimate the optimal monitoring frequency (OMF) to guarantee and predict the minimum number of species occurrences for studies concerning marine ecosystems. The OMF is estimated using the temporal number of zooplankton species through bi-weekly monitoring of zooplankton species data according to operational taxonomic units in the Tongyoung coastal sea. The optimal model comprises two terms, a constant (optimal mean) and a cosine function with a one-year period. The confidence interval (CI) range of the model with monitoring frequency was estimated using a bootstrap method. The CI range was used as a reference to estimate the optimal monitoring frequency. In general, the minimum monitoring frequency (numbers per year) directly depends on the target (acceptable) estimation error. When the acceptable error (range of the CI) increases, the monitoring frequency decreases because the large acceptable error signals a rough estimation. If the acceptable error (unit: number value) of the number of the zooplankton species is set to 3, the minimum monitoring frequency (times per year) is 24. The residual distribution of the model followed a normal distribution. This model can be applied for the estimation of the minimal monitoring frequency that satisfies the target error bounds, as this model provides an estimation of the error of the zooplankton species numbers with monitoring frequencies.

• ETRI Journal
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• 제30권3호
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• pp.461-468
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• 2008

This paper presents a chromatic dispersion monitoring technique using a clock-frequency component for carrier-suppressed return-to-zero (CSRZ) signal. The clock-frequency component is extracted by a clock-extraction (CE) process. To discover which CE methods are most efficient for dispersion monitoring, we evaluate the monitoring performance of each extracted clock signal. We also evaluate the monitoring ability to detect the optimum amount of dispersion compensation when optical nonlinearity exists, since it is more important in nonlinear transmission systems. We demonstrate efficient CE methods of CSRZ signal to monitor chromatic dispersion for optimum compensation in high-speed optical communication systems.