• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제55권4호
• /
• pp.189-198
• /
• 2006

In order to improve the reliability of stator windings for hydro generators, it is necessary to detect the defective point and life assessment of the high voltage windings. Especially the on-line partial discharge (PD) test provides the ability to monitor effects, such as slot discharge, internal discharge, and end-winding discharge without interrupting generators, this method has been proven the major testing technology in high voltage rotating machines nowadays. The purpose of this paper is to describe the method of the on-line PD measurement on stator windings for hydro-generator with 13 [kV] class ceramic coupler (CC), on-line PD measuring system, terminal box, and index parameters. Also, the developed PD measuring system and 13 [kV] class CC were installed Daechung-dam generator #2. It was found that this installed sensor and system had good electrical characteristics to detect PD activity during the operating condition with its detection frequency band is between several and several tens MHz.

• Journal of Electrical Engineering and Technology
• /
• 제4권1호
• /
• pp.123-130
• /
• 2009

The partial discharge (PD) measurement is a very effective method to assess the winding insulation condition of high-voltage machines, since most of the insulation failure processes are directly or indirectly caused by PD. On-line PD measurements, which can detect insulation defects of winding in the early stages on rotating machines in operation, have been accepted as the most important technique. The epoxy mica capacitive coupler is currently and extensively used for on-line detection of PD pulses of high-voltage rotating machines. To evaluate the feasibility of developing a capacitive coupler that is easier to manufacture at a lower cost compared to epoxy mica couplers, a 100pF capacitive coupler made of ceramic material is designed, fabricated and tested for on-line PD measurements of 23 kV electrical machines. A series of electrical tests and accelerated aging tests are performed on the ceramic coupler to evaluate the performance requirements, long-term reliability and thermal stability for in field application. The test results show that the newly developed ceramic coupler provides equal and improved performance at a lower cost compared to epoxy mica couplers, and estimated voltage life is anticipated to surpass 100 years.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1972-1973
• /
• 2007

A field-oriented UHF system for on-line PD monitoring of transformers is designed, which has been installed inside the oil tank of a transformer. This system has successfully captured long intermittent discharge signals that hadn't been detected through conventional techniques, and solved the problem successfully. The results demonstrate that UHF technique has great advantages for on-line PD monitoring of transformers. By adopting the peak detection technique, it becomes easy and effective for the transplantation of the phase-resolved pattern recognition technique from conventional method to UHF method, and then to realize continuous on-line monitoring, source characterization and trending analysis.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제48권1호
• /
• pp.45-50
• /
• 1999

This paper describes a partial discharge (PD) on-line monitoring system used for large turbine generators. The system consists of a broadband current transducer, a computer-aid PD measurement system. By using a programmable fabricate band pass filter and an adaptive digital filter, the system can suppress the noise and extract PD signal from the intense noise surroundings successfully. Two simulated PD sources, which often exist in the large generators, were simulated and detected. At the end of this paper, some field test results, obtained from a 200MW generating set, were presented and discussed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 C
• /
• pp.1694-1696
• /
• 2001

Partial discharge(PD) tests are used to evaluate the insulation condition of stator windings in six 6.6kV motors. These tests were conducted using a conventional partial discharge detector (PDD), turbine generator analyzer(TGA) and partial discharge analyzer(PDA). Off-line PD measurements were performed on six 6.6kV motors. PD magnitudes ranged from 740 pC to 5,100 pC at the normal line-to-ground voltage. Six 6.6kV motors have been equipped with eighteen 80pF epoxy-mica couplers(one per phase) on the motor terminal boxs. The PD pulse from sensors were measured with the TGA and PDA instruments on a normally operating motors. The PDD, TGA and PDA test results showed that internal discharge was detected in voids of the groundwall insulation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 E
• /
• pp.2089-2092
• /
• 1999

Partial discharge(PD) tests were performed both when the pumped storage generator(rated 13.8kV and 220MVA) was on-line and off-line. This generator has been equipped with 12 bus coupler sensors in directional mode. PD tests were conducted using partial discharge analyzer(PDA), partial discharge meter(PDM) and digital partial discharge detector. PDA showed that the patterns of the normalized quantity number(NQN) and the partial discharge magnitude are in accord with on-line and off-line. The insulation condition was estimated by diagnostic tests(off-line) such as PD magnitude and dissipation factor.

• 한국전기전자재료학회논문지
• /
• 제18권8호
• /
• pp.766-771
• /
• 2005

In this study, PD(partial discharge) signals which occur at stator coil of traction Motor are acquired these data are used for classifying the PD sources. NN(neural network) has recently applied to classify the PD pattern. The PD data are used for the learning process to classify PD sources. The PD data come from normal specimen and defective specimens such as internal void discharges, slot discharges and surface discharges. PD distribution parameters are calculated from a set of the data, which is used to realize diagnostic algorithm. NN which applies distribution parameters is useful to classify the PD patterns of defective sources generating in stator coil of traction motor.

• 센서학회지
• /
• 제32권4호
• /
• pp.219-222
• /
• 2023

Partial discharges (PD) have long been recognized as a major contributing factor to catastrophic failures in high-power equipment. As the demand for high voltage direct current (HVDC) facilities continues to rise, the significance of on-line and real-time monitoring of PD becomes increasingly prominent. In this study, we have designed, fabricated, and characterized a highly sensitive and cost-effective PD sensor comprising a pair of copper electrodes with different arc lengths. The key advantage of our sensor is its non-invasive nature, as it can be installed at any location along the entire power cable without requiring structural modifications. In contrast, conventional PD sensors are typically limited to installation at cable terminals or insulation joint boxes, often necessitating invasive alterations. Our PD sensor demonstrates exceptional accuracy in estimating PD location, with a success rate exceeding 95% in the straight sections of the power cable and surpassing 89% in curved sections. These remarkable characteristics indicate its high potential for realtime and on-line detection of PD.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.527-528
• /
• 2007

A field-oriented UHF system for on-line PD monitoring of transformers is designed, which has been installed inside the oil tank of a 220kV transformer in a substation. This system has successfully captured long intermittent discharge signals that hadn't been detected through conventional techniques, and solved the problem successfully. The results demonstrate that UHF technique has great advantages for on-line PD monitoring of transformers. By adopting the peak detection technique, it becomes easy and effective for the transplantation of the phase-resolved pattern recognition technique from conventional method to UHF method, and then to realize continuous on-line monitoring, source characterization and trending analysis.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제5C권6호
• /
• pp.223-227
• /
• 2005

Insulation failure of traction motor stator coil depends on the continuous stress imposed on it and knowing its insulation condition is an issue of significance for proper safety operation. In this paper, application of the NN (Neural Network) as a scheme of the off-line PD (partial discharge) diagnosis method that occurs at the stator coil of a traction motor was studied. For PD data acquisition, three defective models were made; internal void discharge model, slot discharge model and surface discharge model. PD data for recognition were acquired from a PD detector. Statistical distributions and parameters were calculated to perform recognition between model discharge sources. These statistical distribution parameters are applied to classify PD sources by the NN with a good recognition rate on the discharge sources.