• Journal of the Korean Society for Nondestructive Testing
• /
• v.35 no.1
• /
• pp.31-38
• /
• 2015

Intelligent leak detection is an essential component of a underground water supply pipeline network such as a smart water grid system. In this network, numerous leak detection sensors are needed to cover all of the pipelines in a specific area installed at specific regular distances. It is also necessary to determine the existence of any leaks and estimate its location within a short time after it occurs. In this study, the leak signal properties and feasibility of leak location detection were investigated when concurrent leaks occurred at two points in a pipeline. The straight distance between the two leak sensors in the 100A sized cast-iron pipeline was 315.6 m, and their signals were measured with one leak and two concurrent leaks. Each leak location was described after analyzing the frequency properties and cross-correlation of the measured signals.

• Journal of Electrical Engineering and Technology
• /
• v.11 no.1
• /
• pp.86-92
• /
• 2016

Upon detecting a frequency event in a power system, the stepwise inertial control (SIC) of a wind turbine generator (WTG) instantly increases the power output for a preset period so as to arrest the frequency drop. Afterwards, SIC rapidly reduces the WTG output to avert over-deceleration (OD). However, such a rapid output reduction may act as a power deficit in the power system, and thereby cause a second frequency dip. In this paper, a hybrid reference function for the stable SIC of a doubly-fed induction generator is proposed to prevent OD while improving the frequency nadir (FN). To achieve this objective, a reference function is separately defined prior to and after the FN. In order to improve the FN when an event is detected, the reference is instantly increased by a constant and then maintained until the FN. This constant is determined by considering the power margin and available kinetic energy. To prevent OD, the reference decays with the rotor speed after the FN. The performance of the proposed scheme was validated under various wind speed conditions and wind power penetration levels using an EMTP-RV simulator. The results clearly demonstrate that the scheme successfully prevents OD while improving the FN at different wind conditions and wind power penetration levels. Furthermore, the scheme is adaptive to the size of a frequency event.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.1
• /
• pp.155-161
• /
• 2015

The energy storage system is actively used as the widespread of smart grid. In the case of large scale EES, it can be efficiently controlled linked with BEMS or BAS. But, in the case of EES installed in a small sized household, it needs the help of the remote control system because it lacks the expert for controlling and operating of EES. In addition, in the case when the solar energy generation and EES are installed at the same time, a small sized EMS which can be efficiently controlled depending on the solar energy generation or electric power load is needed. In this paper, the EMS which can efficiently control the solar power generation as well as EES installed in a small sized household is implemented and its usefulness is verified through some experimental studies.

• Journal of Internet Computing and Services
• /
• v.18 no.1
• /
• pp.21-26
• /
• 2017

In this paper, an USB-OTG (Uiversal Serial Bus On-the-go) interface module was designed with the iris information for personal identification. The image recognition algorithm which was searching face and iris areas, was proposed with pixel differences from eye blinking after several facial images were captured and then detected without any activities like as pressing the button of smart phone. The region of pupil and iris could be fast involved with the proper iris area segmentation from the pixel value calculation of frame difference among the images which were detected with two adjacent open-eye and close-eye pictures. This proposed iris recognition could be fast processed with the proper grid size of the eye region, and designed with the frame difference between the adjacent images from the USB-OTG interface with this camera module with the restrict of searching area in face and iris location. As a result, the detection time of iris location can be reduced, and this module can be expected with eliminating the standby time of eye-open.

• Environmental and Resource Economics Review
• /
• v.24 no.1
• /
• pp.225-249
• /
• 2015

There are growing interests in the introduction of consumer's selective electricity tariff systems in order to enhance demand response in electricity market in Korea. Real time pricing (RTP) and Time of Use (TOU) are typical examples of demand response system through which electricity price is linked to real time demand. This paper adopts an agent-based model to analyze the effects of such demand system on the counsumers' electricity costs. The result shows that real time pricing system is effective to reduce electricity costs of consumers by providing more flexible tariff system, depending on each consumer's demand pattern. This finding could be used as a basis for supporting smart grid system in the presence of responsive demand environment.

• Journal of IKEEE
• /
• v.24 no.1
• /
• pp.208-215
• /
• 2020

In this study, the output 380V direct current DC-DC converter for low-voltage direct current(LVDC) distribution was designed in three types, and the voltage and current characteristics of the three types of DC-DC converter were compared and analyzed through simulation. When the converter was configured using a parallel structure with the power metal-oxide semiconductor field-effect transistor and two current suppression insulated-gate bipolar transistors(IGBTs), the time when the output voltage was stabilized at DC 380V was relatively short with 9ms and the range of output current changes was also between 44.8A and 50.2A, indicating that the width of change was much smaller and the effect of current suppression was greater compared to when IGBT was not applied(68~83A). These results suggest that the proposed DC-DC converter for LVDC distribution is likely to be applied to smart grid construction.

• The Journal of Bigdata
• /
• v.5 no.1
• /
• pp.97-108
• /
• 2020

As the domestic electric power industry becomes a smart grid, big data platforms for demand management, facility management, and customer service have been deployed. However, due to the nature of the big data project, big data platforms take time to realize their value in the business processes. Therefore, it is not easy to evaluate the performance of the initial big data platforms using the known or theoretical evaluation methods. In this paper, we propose a methodology of big data platform performance evaluation based on specific information quality such as information completeness/sufficiency, information reliability, information relevancy, information comparability, information unbiasedness, timeliness of information, related to the volume, diversity, and velocity of big data.

• KIPS Transactions on Computer and Communication Systems
• /
• v.1 no.3
• /
• pp.171-180
• /
• 2012

In the development of MDMS(Meter Data Management System) based on CIM(Common Information Model), which is international standard in information model and data exchange on power system, the two focused issues are the effective management of data collected in a shorter time period and the way to integrate services supporting legacy system to use the AMI(AMI, Advanced Metering Infrastructure) data. In this paper, we propose MDMS implementation methods and functions in AMI environment which are differ from existing AMR system environments in that the methods support bi-directional service infrastructure. The proposed MDMS in this paper has two unique features, one is the secure of interoperability by utilizing the CIM and ESB, the other is the improvement of field application by implementing system module based on components. On an implementation of smart grid, the result of proposed methods is expected to contribute to the efficient development and operation of CIM-based power system.

• Journal of IKEEE
• /
• v.23 no.2
• /
• pp.495-501
• /
• 2019

This paper proposes a variable passive harmonic filter for reduction and improvement of harmonics and power factor of single-phase uninterruptible power supply(UPS) with full bridge rectifier. Recently, UPSs have excellent harmonic and power factor operation characteristics by applying 2-level or more levels of power conversion methods. On the other hand, the single-phase UPS of the full bridge rectifier seriously causes the third, fifth, and seventh harmonics, and the power factor reduction on the grid side. Therefore, we present a variable passive harmonic filter for eliminating (2n+1) order harmonics and improving the power factor generated by the full bridge rectifier operation. In order to evaluate the performance of the proposed variable harmonic filter, the its validity is verified by various simulations and experiments.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.3
• /
• pp.441-448
• /
• 2022

In the distribution system, there are multiple power protection systems such as circuit breakers at substations, and reclosers, minimum circuit ampacities, fault interrupters on distribution lines. They are widely used to prevent partial outages, cascading power failure or blackout so that other healthy systems could maintain the integrity in case of the instant fault or permanent failure on the power lines. However, when a fault happens, it could cause a major black out due to the lack of the protection cooperation between the protection relay of the circuit breaker at a substation and a protection system on the distribution lines. To achieve the power system integrity better, it is required to develop the circuit breaker which can be operational within 1 cycle(16ms). In this study, the high speed circuit breaker which is filled up with eco-friendly gas is developed. This equipment achieved an excellent test results based on IEC 62271-111 standard. It is respected that this equipment would contribute to prevent the wide area blackout by isolating a fault area quicker and faster.