• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.81-88
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• 2013

A low voltage circuit breaker protects electrical equipments from over current and short faults of system by cutting the power supply. The breaker use a thermal magnetic type trip device from the past. In recent years, electronic type relays are applied due to useful functions and services. The purpose of this development is full digitalizing of relay functions of a low voltage breaker. It includes separation of current sensor from current transformer, digital signal processing, high speed relaying, and voltage measuring for power meter. The suggestions are tested and implemented by making prototype and testing its all relay functions.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.284-290
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• 2000

The measurement of electric current using optical techniques provides a number of important practical advantages including effective isolation from high line potentials and freedom from the saturation effects observed in conventional current transformers. In this work the optical current sensor which uses thin YIG(Yittrium Ion Garnet) film as a Faraday element has been developed. We have characterized this optical current sensor and implemented it to the OOCR(Opto-electronic OverCurrent Realy) Performance of the OOCR shows the possibility of replacing the present overcurrent relays with OOCR.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.46-53
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• 2022

This paper presents the design and manufacture of a Solid State Relay (SSR) life prediction device that can predict the lifetime of an SSR, which is a key component of a glass forming machine. The lifetime of an SSR is over when the current supplied to the relay is overcurrent (20 A or higher), and the operating time is 100,000 h or longer. Therefore, the life prediction device for the SSR was designed using DSP to accurately read the current and temperature values from the current and temperature sensors, respectively. The characteristic test of the manufactured non-contact relay life prediction device confirmed that the current and temperature were safely measured. Thus, the SSR lifetime prediction device developed in this study can be used to predict the lifetime of an SSR attached to a glass forming machine.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.741-742
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• 2011

In this paper, an over-current relay algorithm module for a network-based protective relay simulator is proposed. The proposed protective simulator is based on the client-sever paradigm. The module composed of a server and user interface provides a network-based simulation environment.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.451-465
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• 2008

The DC over current relay(76i) and the DC under voltage relay(mid-point relay, 80A) used mainly with DC protective relay system of DC electric railway in Korea, But the DC fault selective relay(50F) is applying to recently mainly. In this study, simulation to compare 76i/80A and 50F in the methods of protection and the operational characteristics were executed through verifying a calculation of short circuit current and using PSCAD/EMTDC transition program. As a result of this study, it was proved that while 80A runs in relation to the scale of fault resistance, 50F runs regardless of the scale of fault resistance or the length of rail.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.195-196
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• 2008

Output of wind generators are changed by windy level. The change of the output also affects the amplitude of fault current. And this fault current causes OCR's mal-operation. To solve the problem, this paper adopts that Over Current Relay adapted for Decentralized generator algorithm.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.56-64
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• 2011

In this paper, the characteristics of LCL set-up parameters for the satellite load distribution are analyzed under the electrical system environment, implemented the LCL circuits and evaluated the performance and its behaviour. Recently, it is implemented the load distribution circuit by latching current limiter(LCL) rather than conventional fuse and relay for the protection of the satellite power system from a fault load. The LCL circuit is composed of the electrical components, not mechanical parts with the fuse and relay. When detected the over current on a fault load, it is activated to maintain the trip-off level for set-up time and then cut-off the load power by the active control. It is more flexible and provided a chance to reuse of the load in case of temporarily event, but the fuse and relay can't be used again after activating due to the physical disconnection. However, for implementation of LCL circuit, it should be carefully considered the behavior of the LCL circuit under the worst electrical system environment and applied it to define the set-up parameters related with over-current inhibition.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.173-175
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• 2005

Malfunction of Klippon relay in Cheju-Haenam HVDC system has been caused by the inflow of high voltage arc. In this paper, we have studied on the theoretical examination and data analysis of Klippon relay, and the countermeasures against the problems were suggested according to their causes. Grounding problem in Klippon relay is removed by one-point earth connection and by modification of grounding circuit. The effects of over current surge was removed by attaching blocking diodes by series In Klippon relay to remove surge input in Klippon relay's mercury contact. The problem of Induced overvoltage by 86re1ay excitation coil, was removed by attaching Free-wheeling diode in parallel with the excitation coil of Lock-out relay.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1000-1002
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• 1997

In this paper we proposes a scheme which can improve the detecting capability of the high impedance fault of the conventional distance relaying. It utilizes the directional ground overcurrent relay called HIFR together with the distance relay in order to secure the security and selectivity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.11
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• pp.1873-1878
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• 2007

Current differential relays may maloperate during magnetic inrush and over-excitation because a significant differential current is produced. To prevent maloperation, the relays adopt some harmonic components included in the differential current. The harmonic restraints may increase the security of a relay but cause the operating time delay of a relay when an internal fault occurs. Moreover, the operating time delay is more increased if a current transformer (CT) is saturated. This paper describes a current differential relaying algorithm for power transformer protection with a compensating algorithm for the secondary current of a CT. The comparative study was conducted with and without the compensating algorithm. The performance of the proposed algorithm was investigated when the measurement CT (C400) and the protection CT (C400) are used. The proposed algorithm can compensate the distorted current of a CT and thus reduce the operating time delay of the relay significantly for an internal fault with CT saturation.