• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1229-1231
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• 2002

This paper presents the design of DC protection system of Light Rail Transit system. Especially, the composition and interface for DC Switchgear. Digital protection unit and sort of protection algorithm are focused. DC Switchgear (DCSWGR) for LRT testline consist of 5 different panels with peculiar characteristics are examined. Also Basic actuation principle for DC fault select relay (50F), Line Test Device (LTD), DC Overcurrent(OCR) relay are introduced.

• 전기의세계
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• v.27 no.6
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• pp.54-57
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• 1978

An analytical investigation has been carried out for the motion of moving element in electro-dynamometer type directional power relay under A.C source. For the more a time dependent kinetic performance of the element can also be deduced for the D.C component in fault current. The results obtained thus for show that, in the relay with stopper, the performance time for the equal D.C and A.C component can be shorten ca. 0.5Hz in comparison with the fact, the performance time exhibits to delay ca. 0.75Hz under the same conditions for the case of the relay without stopper, it appear that these differences of performance times will not give vise any difficultys for the apects of practical case, however, the obtain results can be applicable in the course of the design of the relay.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1948_1949
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• 2009

All the power generating station require dc auxiliary power systems to operate those dc components that must be available if a loss of ac power occur. Some examples of such components are auxiliary motors, circuit breakers, relays and solenoids. The dc source may be one common battery for both power and control or two separate batteries; one for power and another for control. Typically, a dc auxiliary power system is designed as an ungrounded system, instead of grounded system, so that a low-resistance ground fault on one of its two polarities will not affect the operation of the system, thus increasing system reliability and continuity of service. A ground detector should provide a high polarity-to-ground resistance so that a single ground fault occurring on the system will not affect the operation of that system. Sensitive relays have been known to energize momentarily while the cable and capacitive charge to ground shifts[1]. A power station had experienced this kind of incident and performed root cause analysis based on PC based simulation program known as PSpice. This simulation showed adapted relays on the system energize momentarily and design criteria on this relay should be corrected.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.2
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• pp.67-73
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• 2015

Distance relay is widely used for the protection of long transmission line. Most of distance relay used to calculate line impedance by measuring voltage and current using DFT. So if there is a computation error due to the influence of phasor by DC offset component, due to excessive vibration by measuring line impedance, overreach or underreach can be occurs, and then abnormal and non-operation of distance relay can be issue. It is very important to implement the robust distance relaying that is not affected by DC offset component. This paper describes an enhanced distance relaying based on the DC offset elimination filter to minimize the effects of DC offset on a long transmission line. The proposed DC offset elimination filter has not need any prior information. The phase angle delay of the proposed DC offset filter did not occurred and the gain error was not found. The enhanced distance relay uses fault current as well as residual current. The behavior of the proposed distance relaying using off-line simulation has been verified using data about several fault conditions generated by the ATP simulation software.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.25-34
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• 2019

Recently, when a fault occurs at a long-distance point in a LVDC (low voltage direct current) distribution feeder in a light rail system, the magnitude of the current can decrease to less than that of the load current of a light rail system. Therefore, proper protection coordination method to distinguish a fault current from a load current is required. To overcome these problems, this paper proposes an optimal algorithm of protection devices for a LVDC distribution feeder in a light rail system. In other words, based on the characteristics of the fault current for ground resistance and fault location, this paper proposes an optimal operation algorithm of a selective relay to properly identify the fault current compared to the load current in a light rail system. In addition, this paper modelled the distribution system including AC/DC converter using a PSCAD/EMTDC S/W and from the simulation results for a real light rail system, the proposed algorithm was found to be a useful and practical tool to correctly identify the fault current and load current.