• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.6
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• pp.275-278
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• 2001

This paper presents an algorithm for detecting current transformer (CT) saturation. At the instants of beginning (or end) of saturation, as a magnetizing inductance of the core is changed significantly, the shapes of the secondary current are also changed significantly though secondary currents are continuous the instants. At the instants, the second-order of third-order difference of the secondary current has big values. Thus, the third difference of the current is used to detect the beginning/end of CT saturation in this paper. If the magnitude of third-order difference of the secondary current is larger than a threshold value, the CT begins of ends saturation at the instants. The proposed detection method is unaffected by the amount of residual flux. The results of various tests with residual flux from -80% to +80% indicate satisfactory performance of the method.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.64-66
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• 2000

This paper presents an algorithm for detecting current transformer (CT). At the instants of beginning and end of saturation, the increment of the secondary current is reduced significantly, depending on the residual flux and saturation time. Thus, the third difference of the current is used to detect saturation in this paper. If the third difference is less than threshold the CT is at the beginning/end of saturation. The proposed detection method is unaffected by the amount of residual flux. The results of various tests with residual flux from -80% to +80% indicate satisfactory performance of the method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.879-884
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• 2009

A Method for detection of saturation of a current transformer(CT) is proposed. The algorithm is initiated when the end point of a saturation period is detected. This detection is achieved by checking the time interval between the adjacent zero-crossing points of the second derivative of the secondary current. Once the end point of the saturation period is detected, the beginning point of the corresponding saturation period is determined by backward examination of the sum of the secondary current from the end point. The performance of the algorithm was evaluated for a-g faults on a 345 kV 100km overhead transmission line. The Electromagnetic Transient Program(EMTP) was used to generate fault current signals for different fault inception angles and different remanent fluxes. The performance evaluation shows that the proposed algorithm successfully detects the saturation period even in the presence of a remanent flux.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.10
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• pp.495-501
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• 2002

A difference based current transformer (CT) saturation detection algorithm uses the third difference of a secondary current to detect the instants of the beginning/end of saturation. The third difference of a secondary current contains high frequency components when a CT is saturated. Thus, an effect of an anti-aliasing lowpass filter implemented in digital protection relays on the detection algorithm should be studied. This paper describes performance analysis of a lowpass filter on the CT saturation detection algorithm. The cutoff frequency of the lowpass filter is normally set to be half of a sampling frequency. In this Paper, two sampling frequencies of 3,840 (Hz) corresponding to 64 sample/cycle (s/c) and 1,920 (Hz) corresponding to 32 (s/c) are studied; the cutoff frequencies of the lowpass filters are set to be 1,920 (Hz), 960 (Hz) and 960(Hz), 480(Hz), respectively. And the proposed algorithm is verified by experiment. A 2nd order Butterworth filter is designed as a lowpass filter. The test results and experiment results clearly indicate that the saturation detection algorithm successfully detects the instants of the beginning/end of saturation even though a secondary current is filtered by the designed lowpass filters.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.249-251
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• 2001

This paper presents performance analysis on a low pass filter of a CT saturation detecting algorithm using difference. At the instants of beginning/end of saturation, the shapes of the secondary current are changed significantly though secondary currents are continuous. At the instants, the second-order or third-order difference of the secondary current has big values because of discontinuity of the first order difference. Thus, the third difference of the current is used to detect the beginning/end of CT saturation. An antialiasing low pass filter removes high frequency components and causes phase lag. A CT saturation detecting algorithm using difference of CT secondary currents is affected by the low pass filter. The algorithm is tested with cutoff frequencies of the filter for the two sampling rates of 64[S/C] and 32 [S/C]. The results of various test cases indicate satisfactory performance of the algorithm.

• Journal of The Korean Dental Society of Anesthesiology
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• v.6 no.2 s.11
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• pp.89-97
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• 2006

Background: The aim of this study was to examine the difference of $SpO_2$, PR, $EtCO_2$, RR with submucosal injection of midazolam to oral chloral hydrate and hydroxyzine for pediatric patients Methods: Thirty two sedation cases were performed in this study. Patients were randomly classified into one group taking oral CH (60 mg/kg). hydroxyzine (1 mg/kg) and submucosal injection of midazolam (0.1 mg/kg) and the other group recieving oral CH (50 mg/kg), hydroxyzine (1 mg/kg) and submucosal injection of midazolam (0.2 mg/kg). For evaluating the depth of sedation. data including saturation percentage of oxygen ($SpO_2$), pulse rate (PR), end-tidal carbon dioxide ($EtCO_2$), respiratory rate (RR) and the behavior scale were checked every 2 minutes and were collected for only 40 minutes from the beginning of treatment and were analyzed using Two independent sample T-test. Results: Analysis showed no significant difference in the mean $SpO_2$, PR, $EtCO_2$, RR during sedation between two groups (P > 0.05). The values of $SpO_2$, PR, $EtCO_2$ and RR for both groups remained within the normal values. Conclusions: The results of this present study indicate that combination of oral CH, hydroxyzine, nitrous oxide gas inhalation and submucosal injection of midazolam improved the sedation quality without compromising safety.