• KIEE International Transactions on Power Engineering
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• v.3A no.2
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• pp.70-78
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• 2003

This paper describes a transformer protection relay based on induced voltages. The ratio of the induced voltages of the primary and secondary windings is equal to the turns ratio during normal operating conditions such as magnetic inrush, overexcitation, and steady state, but it differs from the turns ratio in the case of internal faults. For a single-phase and a three-phase Y-Y transformer, the induced voltages are estimated and the ratios are compared with the turns ratio. For three-phase Y-Δ transformers, the differences between the induced voltages are estimated to use the line currents because delta-winding currents are practically unavailable. The proposed relay is tested under various conditions such as magnetic inrush, internal winding faults, overexcitation, and different core characteristics. The results evidently indicate that the relay successfully discriminates internal faults from magnetic inrush and overexcitation. This paper concludes by implementing the relay into a TMS320C6701 digital signal processor and reports satisfactory results. The relay requires no hysteresis data and can reduce the operating time of a relay.

• Journal of electromagnetic engineering and science
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• v.8 no.4
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• pp.148-152
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• 2008

This paper describes the characteristics of lightning-induced voltages on subscriber telecommunication lines in Korea. Lightning parameters such as peak voltage, rise time, decay time, and steepness of the wave front were statistically analyzed from the measured results obtained using a waveform memory system. An induced voltage measurement system was also developed and installed at 286 sites in Korea to collect the induced voltage data. The distributions of lightning-induced voltages were also analyzed using these data.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.10
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• pp.524-530
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• 2000

This paper presents a transformer protective relaying algorithm using the ratio of induced voltages. The proposed algorithm calculates primary and secondary voltage from currents and voltages of primary and secondary windings. The ratio of primary and secondary induced voltages is equal to the turn ratio in case of the steady state and magnetic inrush. On the other hand, the ratio is different form the turn ratio in case of internal winding faults. The algorithm does not require B-H curve and can reduce the relay's operating time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.983-988
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• 2009

This paper analyzed the induced voltages on a telecommunication line due to high-speed a.c. electrified railway system. The induced voltages were measured by domestic regulation, 2 test lines with 2 km length were installed near railway in parallel to compare the influence for distance from disturbing line. The analysis was made on the induced voltages with the distance from railway, line length, and the different earthing point, and also on the waveform and spectrum distributions. The statistical induced voltages for the time for a day and dates was analyzed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.3
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• pp.173-178
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• 2003

This paper proposes a three-winding transformer protective relaying algorithm based on the ratio of the induced voltages (RIV). The RIV of the two windings is the same as the turn ratio for all operating conditions except an internal fault. For a single phase and a three-phase transformer containing the wye-connected windings, the induced voltages of the windings are estimated. For a three-phase transformer containing the delta-connected windings, the induced voltage differences are estimated using the line currents, because the winding currents are practically unavailable. The algorithm can identify the faulted phase and winding if a fault occurs on one phase of a winding. The test results clearly show that the algorithm successfully discriminates internal winding faults from magnetic inrush. The algorithm not only does not require hysteresis data but also can reduce the operating time of a relay.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.71-78
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• 2008

In this paper, The voltage waveshapes and the lightning parameters such as peak voltage, rise time, decay time and steepness of the front wave were statistically anal zed from the lightning-induced voltages measured on subscriber telecommunication line by lightning. Induced voltage measurement system to measure and collect the lightning-induced voltages in several regions of Korea was developed and installed in several sites. The distributions of lightning-induced voltages for Tears, regions and seasons were analyzed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.6
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• pp.253-259
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• 2002

This paper deals with the effects of grounding conductors for metal oxide surge arresters. When surge arresters are improperly installed, the results can cause costly damage of electrical equipments. In particular, the route of surge arrester connection is very important because bends and links of leads increase the impedances to lightning surges and tend to nullify the effectiveness of a grounding conductor. Therefore, there is a need to know how effective installation of lightning surge arresters is made in order to control voltage and to absorb energy at high lightning currents. The effectiveness of a grounding conductor and 18 [㎸] metal oxide distribution line arresters was experimentally investigated under the lightning and oscillatory impulse voltages. Thus, the results are as follows; (1) The induced voltage of a grounding conductor is drastically not affected by length of a connecting line, but it is very sensitive to types of grounding conductor. (2) The coaxial cable having a low characteristic impedance is suitable as a grounding conductor. (3) It is also clear from these results that bonding the metal raceway enclosing the grounding conductor to the grounding electrode is very effective because of skin effect. (4) The induced voltages of grounding conductors for the oscillatory impulse voltages are approximately twice as large as those for the lightning impulse voltages.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.168-170
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• 2000

This paper presents a protective relaying algorithm for transformers using the ratio of induced voltages. The ratio primary and secondary induced voltages calculated calculates from currents and voltages of primary and secondary windings is used. In case of the steady state and magnetic inrush, it is equal to the turn ratio while it is different from the turn ratio in case of internal winding faults. The proposed algorithm operates satisfactorily even large residual flux.

• Journal of Power Electronics
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• v.14 no.5
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• pp.859-865
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• 2014

This study presents an electromagnetic model for predicting shaft voltages in a 2-pole field-excited synchronous generator. After the first observations on shaft voltages were made more than a century ago, extensive work has been conducted on eliminating, mitigating, and integrating the aforementioned phenomena. Given that emphasis has been placed on modeling shaft- and bearing-induced voltages in AC motors driven by variable frequency drives, similar efforts toward a model that is dedicated to generators are insubstantial. This work endeavors to improve current physical interpretation and prediction methods for shaft-induced voltages in generators through semi-analytical derivation. Aside from the experimental validation of the model, investigations regarding the behavior of shaft voltages under varying machine complexities and operating conditions clarify previous uncertainties regarding these phenomena. The performance of the numerical method is also assessed for application in eccentricity fault diagnosis.

• Journal of electromagnetic engineering and science
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• v.1 no.1
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• pp.88-94
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• 2001

In this paper, the lightning-induced voltages on shielded twisted-pair wires with multipoint grounding on cable sheath are calculated by using finite-difference time domain (FDTD) method. The equivalent single-wire line that represents a bundle of twisted-pair wires is adopted for computational efficiency. A finitely conducting ground is also taken into account in both lightning electromagnetic field calculations and surge propagation along the shielded cable for a practical simulation. It is found that multipoint additional grounding on cable sheath provides more shielding effectiveness especially in the early time response of the lightning-induced voltages. From this study, the requirements for lighting surge protection devices in a telecommunication subscriber cab1e can be established.