• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권3호
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• pp.134-141
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• 2006

A potential transformer(PT) has ratio error and phase angle error. Precise measurement of the errors of PT can be achieved using high voltage capacitance bridge, high voltage capacitor and low voltage capacitor. The uncertainty for this method is evaluated and found to be $20{\times}10^{-6}$ in both ratio error and phase angle error. The values measured for PT using the method are well consistent with the those measured for same PT in NMIA(National Measurement Institute of Australia) within the corresponding uncertainty.

• 조명전기설비학회논문지
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• 제23권2호
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• pp.96-102
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• 2009

본 논문에서는 전위강하법을 이용한 접지저항 측정시 전위보조전극의 위치 및 각도의 영향에 대하여 기술하였으며, 측정시 오차를 최소화하는 기법을 제안하였다. 전위강하법은 이론적으로 전위와 전류의 측정원리에 근간을 두고 있으며 측정오차는 주로 보조전극의 위치와 각도에 기인한다. 전위보조전각의 위치에 의한 접지저항 측정값의 상대오차를 분석하기 위해 전류보조전극의 거리를 50[m]로 고정시키고 전위보조전극의 거리를 10[m]에서 50[m]까지 변화시키며 접지저항을 측정하였고 또한 전위보조전극과 전류보조전극 사이의 각도를 30[$^{\circ}$], 45[$^{\circ}$], 60[$^{\circ}$], 90[$^{\circ}$], 180[$^{\circ}$]로 변화시키며 측정하였다. 결과적으로 전위보조전극의 거리 증가 및 전류보조전극과 전위보조전극 사이의 각도가 감소할수록 상대오차가 작게 나타났다. 본 실험결과는 접지시스템의 접지저항을 측정할 때 전위보조전극의 위치를 결정하는데 활용될 수 있다.

• 전기학회논문지
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• 제57권6호
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• pp.1017-1021
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• 2008

A calculable potential transformer(PT) with nominal ratio error in wide range of -10% to +10% has been developed on basis of theoretical calculation of ratio error by the number of windings. The developed PT can be used to evaluate the linearity and accuracy of the PT comparator by comparing both the theoretical and experimental values of the PT which have exactly same ratio errors in nominal and calculated values. The PT has been applied for calibration and correction of the PT comparator up to wide ratio error range of -10% to +10%. This portable PT is very convenient to carry to the power industry for the on-site calibration of the PT comparator.

• 전기학회논문지P
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• 제59권2호
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• pp.222-231
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• 2010

This paper presents numerical analysis of measurement errors of ground electrode using the fall-of-potential method. In order to analyze ground resistance error according to the positions of auxiliary probes, firstly, national and international standards were researched. Secondly, numerical ground resistance error of hemispheric electrode was analyzed according to the locations of auxiliary probes and the angle between probes. Then, error-reduced positions of auxiliary probes were shown according to the distance to auxiliary current probe versus ground electrode size. Finally, error compensation method was presented. The results presented in this paper provide useful information regarding ground resistance error of alternative positions of auxiliary probes in case that the auxiliary probes could not be located at the proper position in such cases as there are buildings, roadblock or underground metallic pipe at that position.

• Nuclear Engineering and Technology
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• 제15권4호
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• pp.229-235
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• 1983

원자력발전소에서 Common Mode Failures (CMFs)가 상당한 관심을 모으고 있다. 이 논문에서는 중복 시스템의 비가용도(Unavailability)에 있어서의 전체 CMFs를 잠재적 CMFs(Potential CMFs)와 의존성 인간 실수에 의한 CMFs (CMFs of dependent human error)로 나누어 이론적으로 고찰하였다. 결론적으로, 인간 실수의 의존성이 높아질수록 전체 CMFs는 의존성 인간실수에 의해서 주로 영향을 받는다고 할 수 있다. 역으로, 인간 실수의 의존성이 낮아질수록, 전체 시스템의 비가용도는 기계적 고장이나 의존성 인간실수보다 잠재적 CMFs에 의해 지배된다고 할 수 있다. 그리고, 중복 시스템의 비가용도에 있어서 전체 CMFs가 기계적 고장보다 주된 요소임도 알 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권6호
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• pp.317-322
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• 2006

A accurate potential transformer(PT) with the nominal ratio errors in the wide range of - 9 % to + 11 % has been developed. The developed wide ratio error PT can be used to evaluate the linearity of the PT comparator by comparing both the theoretical values as standard values and experimental values of the PT. The new method has been successfully applied for calibration and correction in the PT comparator including very low ratio error values from ${\pm}0.005%$ to ${\pm}0.3%$ belonging to industry.

• 한국태양에너지학회 논문집
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• 제32권2호
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• pp.74-86
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• 2012

For the improvement of environmental comfort in the buildings with the blind control, the objective of this study is to prevent the direct glare caused by the daylight inlet. During the process of solar profile prediction, time are significant factors that may cause error and glare during the blind control. This research proposes and evaluates the correction and control method to minimize prediction error. For the local areas with different longitude and local standard meridian, error occurred in the process of the time conversion from local standard time to apparent solar time. In order to correct error in time conversion, apparent solar time should be recalculated after adjusting the day of year and the equation of time. To solve the problems by the potential time errors, control method is suggested to divide the control sections using the calibrated fitting-curve and this method is verified through simulations. The proposed correction and control method, which considered potential time errors by loop lop leap years, could solve the problems about direct glare caused by daylight inlet on the work-plane according to the prediction errors of solar profile. And also these methods could maximize daylight inlet and solar heat gain, because the blocked area on windows could be minimized.

• International Journal of Safety
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• 제7권2호
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• pp.1-6
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• 2008

In this paper, the effects of the position and the angle of the potential probes on the measurements of the ground resistance using the fall-of-potential method are described and the testing techniques for minimizing the measuring errors are proposed. The fall-of-potential method is theoretically based on the potential and current measuring principle and the measuring error is primarily caused by the position and angle of auxiliary probes. In order to analyze the relative error in the measured value of the ground resistance due to the position of the potential probe, the ground resistance was measured for the case in which the distance of the current probe was fixed at 50[m] and the distance of the potential probe was located from 10[m] to 50[m]. Also, the potential probe was located in turn at $30[^{\circ}]$, $45[^{\circ}]$, $60[^{\circ}]$, $90[^{\circ}]$, and $180[^{\circ}]$. As a consequence, relative error decreased with increasing distance of the potential probe and decreasing angle between the current probe and potential probe. The results could help to determine the position of the potential probe during the ground resistance measurement.

• 전기학회논문지
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• 제57권7호
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• pp.1223-1228
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• 2008

While a high frequency source is used for measuring the ground impedance, there are several factors having an effect on the measured value. A primary factor of the measurement error is the ac mutual coupling between current and potential test leads. The mutual coupling causes the test current to induce a voltage into the potential test lead that adds to the actual ground potential rise and produces a significant measurement error as the length of the test leads paralleled is prolonged. In order to avoid the mutual coupling, it is recommended that the ground impedance be measured by angled arrangement of test leads. The mutual impedance due to the inductive coupling with an angle of $90^{\circ}$ was calculated at $0^{\circ}$ by Campbell/Foster Method. With an angle of $180^{\circ}$, the mutual impedance was calculated large value enough to introduce a fairly large margin of error, however, the measured value of ground impedance was close to the value at $90^{\circ}$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권8호
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• pp.347-353
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• 2002

This paper presents an accurate method for measuring the ground resistance in powered grounding system. Most of substations and electric power equipments are interconnected to an extensive grounding network of overhead ground wires, neutral conductors of transmission lines, cable shields, and etc. The parasitic effects due to circulating ground currents and ground potential rise make a significant error in measuring the ground resistance. The test current transition method was proposed to reduce the effects of stray ground currents, ground potential rise and harmonic components in measurements of the ground resistance for powered grounding systems. The instrumental error of the test current transition method is decreased as the ratio of the test current signal to noise(S/N) increases. It was found from the test results that the proposed measuring method of the ground resistance is more accurate than the conventional fall-of-potential method or low-pass filter method, and the measuring error was less than 3[%]when S/N is 10.