• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.593-602
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• 2020

Power cables installed in domestic factories or underground can cause accidents depending on the manufacturing process, installation, and environmental conditions during use. When an accident occurs in a power cable, it can cause enormous economic loss and social confusion. Hence, the importance of preventive management of the cable through diagnosis is increasing to prevent it. Therefore, in this paper, a diagnostic sample cable was produced by simulating a part that could be a problem due to the installation, manufacturing defects, or deterioration of cables that can occur in the field. Dielectric loss Tangent (tan 𝛿; TD), and Partial Discharge(PD) tests were performed. Partial discharge and AC (60Hz) withstand voltage equipment using High-Frequency Current Transformer (HFCT) were applied After applying a VLF (Very Low Frequency) power supply with a frequency of 0.1Hz was applied. As a result, B and C phase defect samples at a 2.0U₀ voltage through the VLF could measure the internal partial discharge in the A-phase normal sample cable from the noise at a 0.5U₀ to 2.0U₀ voltage. In addition, the 1.5U₀ voltage was measured through the AC (60Hz) withstand voltage equipment of the commercial frequency to verify its effectiveness. Partial discharge in the run-off state was measured at a voltage of 1.0U₀, and there was a risk when installing the equipment. AC power equipment showed a difficulty of movement by volume or weight. The diagnostic method, through the VLF of the quadrant state, revealed its safety and effectiveness.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1644-1651
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• 2010

VLF $tan{\delta}$ diagnosis technology is introduced in IEEE Std 400 and proposed as evaluation criterion in an effective way of detecting water tree which mainly causes the failure of XLPE insulated cables. In order to inspect the accuracy of the VLF $tan{\delta}$ method for XLPE insulated power cables in Korean distribution system, diagnosis for 41 cables which were being serviced in the fields has been carried out and they were removed for AC breakdown voltage test after. Regarding the 41 cables, it was hard to confirm any relation between the VLF $tan{\delta}$ values and AC breakdown voltages and also water tree in the insulation was not detected. However, the other cables were failed several days after the diagnosis of the 41 cables. Water trees were found and their VLF $tan{\delta}$ values were also much higher than the criterion of IEEE standard. It has been ascertained that we need to change the IEEE criteria in order to improve the accuracy of detecting water trees by additional analyzing of field examples of failure and case studies from overseas countries and therefore amended VLF $tan{\delta}$ test voltage and evaluation criteria have been proposed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.476-482
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• 2009

This paper describes the development of capacitive sensor for the diagnosis of liquid dielectrics, which is widely used as the electrical insulating oil of transformer, circuit breaker, cable and etc. To survey the dielectric properties of the virgin and aged electrical insulating oils, we utilized the highly precise measuring system, using the principle of cross capacitance. The measured properties were used to determine the design factors of the sensor. Then the factors were optimized with the help of computational analysis. To evaluate diagnosis by the sensor, we performed accelerated thermal aging test about electrical insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor. And to evaluate the hysteresis characteristics with the change of temperature, we constructed a testing system, which was composed with vacuum drying oven, oil chamber and measuring instruments, such as LCR meter, MUX and so forth. Through the results of this investigation, we confirmed the superior characteristics of the newly developed sensor.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.122-124
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• 2004

Recently, power system is getting larger and more complex. When the complex power system has a problem, it is very difficult even for the experts to find out where the problem is and to make a timely decision by operators. There have been many studies on these problems but the results are not good enough for applying to real power system. Therefore power system operators always had to judge the exact state of power system and had to be preparative for the problems that can occur later. We developed new methods that can be applied to complex power system by dividing the system into small modules. By using 'module' we can combine small modules together to make complex power systems and the knowledge base that is applied to fault diagnosis system. As a result, compared to previously developed diagnosis products, operational time has shortened, and the knowledge base becomes simpler and clearer, which made online usage capable. This system can be used as a complementary measure that helps the operator from making any mistakes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.5
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• pp.409-416
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• 2017

In order that multiple wideband RF transmitters which have mission to deliver essential information to aircraft operate at the same time, RF transmitter has a variable sub-carrier frequency to modulate the signal. In case of exposure to weak environment, Wide-band RF transmitter is designed to check component of transmitter that includes antenna BIT to increase system reliability. Normally, Antenna BIT measure the reflection RF power of antenna to check system condition. However, Antenna BIT has a difference that depends on testing frequency to use the long RF cable which is located between the power amp and the antenna. The periodic phenomenon of the reflected antenna power are theoretically explained about dependence on the RF cable length. Based on presented result, suggested measurement methods is effectively able to be applied to diagnosis system condition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.104-108
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• 2009

The insulation aging characteristics and structural analysis test were performed to analyze the correlations among the insulation deterioration, diagnostic results and the breakdown strength for the underground power cables. From the results of the degree of crosslinking test, hot-oil test etc., it could be confirmed that there were no manufacturing defects in the power cables under test. From the results of the water tree test and chemical structural analysis, it could be confirmed that the aging status of cable under test were very poor, especially for B-Phase and the degree of aging was increased in the orders of A, C and B-phase. From the above results, it could be concluded that the insulation aging characteristic analysis results were well consistent with the diagnostic and breakdown test results, and also confirmed that the diagnostic system under consideration was successful to discriminate the bad cables which is likely to cause cable system failure.

• Elastomers and Composites
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• v.33 no.4
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• pp.238-245
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• 1998

In this paper, the electric property was investigated for insulation diagnosis of radiation of EPR electric power cables by partially irradiation with $^{60}Co-{\gamma}$ rays. As the rate of radiation increased from 100Mrad to 200Mrad, charging current and discharging current were increased from $1.03{\times}10^{-7}$(A) to $4.3{\times}10^{-9}$(A). In addition, we found charging current and discharging current of cables subjected to 50% and 16.7% irradiation changed the length of the part 1/2 to 1/6 as in comparison with cables degraded by 100% irradiation. For 22m and 66m of cables which had not been degraded yet, we realized the value of charging current and discharging current of 66m cables is three times higher than 22m cables. From these results, it is demonstrated that the possibility of utilizing charging current and discharging current as the diagnosis method of insulation degradation with irradiating EPR cables by $^{60}Co-{\gamma}$ rays.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.157-163
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• 2017

This system is a diagnosis system that checks whether it causes a partial discharge of a power cable or not. PD(Partial Discharge) is detected by FBDS(Frequency Band Detection Sensor). That is, it means a acoustic sensor capable of detecting each frequency band. The wave shape of PD sound is similar to noise and is systematically generated by partial discharge. Therefore, in this paper, we could discriminate between normal and abnormal case using relative level crossing rate(RLCR) and spectrogram of frequency energy rate.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.14-21
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• 2000

This paper presents the results of performance evaluation of silicone treatment technique which was developed for the insulation rehabilitation of water tree aged XLPE power cables. We treated the water tree aged 325 [$\textrm{mm}^2$] CN/CV cables with silicone, and then analyzed the degree of insulation rehabilitation as a function of time. AC breakdown test was conducted to evaluate insulation rehabilitation. The diagnosis test using relaxation current measurement and the characteristic analysis of insulation were also performed to estimate silicone treated cable. AC breakdown strength of silicone treated cable for one year was increased, resulting from the chemical reaction between silicone fluid and water. This experiment showed that the silicone treatment technique was effective for insulation rehabilitation of the water tree aged cables.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.158-159
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• 2006

The system measuring the Partial discharge(PD) is very essential to investigate the hazard defects in the insulation systems of the high voltage engineering. We included two parts in this discussion; The proposed method of Foil Sensor Array and the normally used method m the practice. Firstly, it will be shown the improved sensitivity of our proposed FSA sensor compare with the existing normal foil sensor. And then, the linearity of detecting sensitivities of various kinds of FSA sensors such as $2{\times}2$, $2{\times}4$, $3{\times}3$ etc. using in our experiments, was shown. From the obtained results, we can see that FSA sensor is more sensitivity than normal foil sensor and the linear increment property of FSA sensitivities.