• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.194-202
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• 2017

In this study, we measured and analyzed electrical noise signals present in devices and systems operated in industrial facilities. Based on the analytic findings, we studied the most effective improvement measures for eliminating such noise signals. Leakage current and ground current generate data interferences in communication systems, and therefore we measured leakage current and ground current. We also measured and analyzed electrical noises in power systems to predict noise pathways and interference routes. Furthermore, we proposed the most effective and reliable improvement measures for blocking off various noise signals and safely eliminating them by improving the internal wiring of the facilities and grounding systems. As a final step, we conducted the proposed improvement measures and confirmed that they helped to improve the operations of the device sand systems in service by re-measuring electrical noise signals and comparing them with those measured before the proposed improvement measures were implemented.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.171-174
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• 2004

Concerning Korean energy consumption, 20% of the total electrical energy (96% is now exported) is consumed in lighting area. Accordingly, it is one of the most important governmental policies to efficiently utilize electricity due to development and application of high-efficiency lighting equipment. In Korea, widely-built traffic signals employ an incandescent and are of 100W/300 mm, and 280,080set/801,932lamps have been installed and operated by 1999. Of them, 58%(161,181set), 25%(69,655set) and 18%(49,244set) correspond to traffic signals, pedestrian signals and other supplementary signals respectively. It was estimated that electrical energy consumed 28MW instantaneously, 245GWH annually. On the other hand, the LED traffic signal is expected to be a future traffic signal since if traffic signals are replaced by LEDs, energy saving effect of 85% and drop of 75% in maintenance fee will be obtained. In this paper, the performance and characteristics of many LED traffic signals made in Korea are summarized in order to reform Korean standard of LED traffic signals.

• Journal of electromagnetic engineering and science
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• v.18 no.4
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• pp.254-260
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• 2018

In this study, we suggest an emulator for generating multiple heterogeneous interference signals in the Korean radio frequency identification/ubiquitous sensor network (RFID/USN) frequency band. The proposed emulator uses only one universal software radio peripheral to generate multiple heterogeneous interference signals more economically. Moreover, the physical and media access control parameters can be adjusted in real time using the LabVIEW program, thereby making it possible to create various time-varying interference environments easily. As an example showing the capability of the proposed emulator, multiple interference signals consisting of a frequency-hopping RFID signal and two LoRa signals with different spreading factors were generated. The generated signals were confirmed in both frequency and time domains. From the experimental results, we verified that our emulator could successfully generate multiple heterogeneous interference signals with different frequency and time domain characteristics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.179-193
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• 2016

In power quality monitoring, voltage fluctuation is one of the power quality problems, which cause light flickers. To determine the flicker severity, the flicker meter concept was developed in an IEC 61000-4-15 standard. Generally, voltage fluctuations are described as an amplitude modulation(AM). The flicker meter of IEC 61000-4-15 as an international standard for flicker measurement recommends square demodulation method to detect flicker signals from voltage fluctuation signals. This paper suggests a new effective method using filter bank to detect and estimate flicker signals, which do not need square demodulation. For the accurate detection of flicker signals, the filter bank is designed with a full consideration of the spectrum characteristics of voltage fluctuation signals described as AM. The frequency and magnitude of the detected flicker signals are estimated using recursive method. Computer simulations were performed on synthesized signals to prove validity of the proposed method.

• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.154-160
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• 2011

A new algorithm for estimating the fundamental frequency of power system signals is presented. The proposed algorithm consists of two stages: orthogonal decomposition and a complex Prony analysis. First, the input signal is decomposed into two orthogonal components using cosine and sine filters, and a variable window is adapted to enhance the performance of eliminating harmonics. Then a complex Prony analysis that is proposed in this paper is used to estimate the fundamental frequency by approximating the cosine-filtered and sine-filtered signals simultaneously. To evaluate the performance of the algorithm, amplitude modulation and harmonic tests were performed using simulated test signals. The performance of the algorithm was also assessed for dynamic conditions on a single-machine power system. The Electromagnetic Transients Program was used to generate voltage signals for a load increase and single phase-to-ground faults. The performance evaluation showed that the proposed algorithm accurately estimated the fundamental frequency of power system signals in the presence of amplitude modulation and harmonics.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.275-277
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• 1993

It is practically required to develop an optical transmission system, for the diagnosis of electric power apparatus, which enables to distinguish the right signals related to the partial discharge taken place inside the apparatus. These partial discharges are transformed into ultra sonic signals by the sensor and then used for the voltage application to pokels cell. Afterwards, the modulated laser beam is transmitted through the optical fiber. Throughout this work, a laser-beam based detecting system is developed and permits us to reproduce the transmitted signals indirectly without electromagnetic interference. For this purpose the characteristics of this system is well analyzed by means of different type of signals from function generator.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.346-349
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• 1993

A method for image compression based on decomposition is presented. We design the efficient coding technique for upper band image signals. This coding technique with directive 1-D DPCM is based on the statistical properties of upper bands. Lower band image signals is encoded using 2-D DPCM. The directive 1-D DPCM is performed, scanning upper bands according to edge direction. And then the predicted error signals of upper band sis coded using B1 and Huffman code, and the predicted error signals of lower band is coded using Huffman code. The proposed system shows improved performance when compared with other existing methods with respect to peak signal to noise ratio(PSMR) and human visual system(HVS) properties.

• Journal of Power Electronics
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• v.16 no.3
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• pp.1190-1199
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• 2016

This study proposes a classification and compensation algorithm of two non-ideal output signals of a resolver to reduce position errors. Practically, a resolver generates position errors because of amplitude imbalance and quadrature imperfection between the two output signals of the resolver. In this study, a digital signal processor system based on a resolver-to-digital converter is used to reconstruct the two output signals of the resolver. The two output signals, "sin" and "cos," can be represented by a unit circle on the xy-plot. The classification and compensation of the errors can be obtained by using the radius and area of the circle made by the resolver signals. The method computes the integration of the areas made by the two resolver output signals to classify and compensate the error. This system cannot be applied during transient response given that the area integration during the transient state causes an error in the proposed method. The proposed method does not need any additional hardware. The experimental results verify the effectiveness of the proposed algorithm.

• Journal of the Optical Society of Korea
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• v.20 no.2
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• pp.223-227
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• 2016

The impact of optical receiver configuration on in-band crosstalk-induced penalty has been investigated in both theoretical and experimental analyses, for differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK) signals. Previously it has been shown that DPSK signals are ~6 dB more tolerant to in-band crosstalk than on-off keying (OOK) signals. However, we find that the tolerance difference between the two signals is reduced to ~3 dB when the decision threshold of the receiver is optimized to minimize the bit-error rate for each signal. Then we derive simple equations for the in-band crosstalk-induced penalty in DPSK and DQPSK signals with two different optical receiver configurations: balanced and single-ended direct-detection receivers. We confirm that the penalties obtained from our simple equations agree well with the measured results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.136-140
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• 1999

Measurements of AE signals caused by partial discharges were performed by using an ultrasonic measurement technique to diagonise the electrical treeing deterioration in XLPE cable. We also examined the partial discharge magnitude and AE signals(peak-to-peak) with the increase of the deterioration time. From these results, it was found that AE signal due to partial discharge can be greatly detected at the peak value of positive polarities prior to the breakdown voltages, and the magnitude of AE signals was closely related to the current pulses by the increase of deterioration, and it appeared that AE signals(peak-to-peak) was proportional to partial discharge magnitude. Attenuation and time-delaying characteristics of ultrasonic signals propagated in various polymers sample by using ultrasonic oscillation and receiving systems are also reported as a basic data of ultrasonic measurements in XLPE cable.