• 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.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.10-11
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• 2006

The fault location is obtained from the distance relay that detects the fault of the transmission line. In this time, transmission line crews track down the fault location and the reasons. However, because of having error at the fault location of the distance relay, there is a discordance between real and obtained fault location. As this reason, the inspection time for finding fault location can be longer. In this paper, we proposed the statistical (regression) analysis method based on each type of relay's the historical fault location data and the real fault distance data to improve the problems. With finding the regression equation based on the regression analysis, and putting the relay fault location into that equation, the real fault distance is calculated. As a result of the Prediction fault location, the inspection time of transmission line can be reduced.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.64-69
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• 2013

For power system protection, the distance relay settings are important. Apparent factor is a necessary parameter in distance relay settings. Apparent factors have to be calculated when setting the distance relays and doing the resetting in case of configuration change in power system. The problem is that the current method to calculate apparent factor requires tools and plenty of time to do fault analysis and this method is complex especially in case of configuration change. Therefore this paper proposes a fast algorithm to calculate apparent factor without the fault analysis. Test results prove that this algorithm is simple and accurate by simulation.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.501-502
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• 2007

This paper describes a distance relay that operates in conjunction with a current transformer (CT) compensation algorithm. A distance relay detects a fault based on the ratio of the voltage to the current. If a CT saturates, the calculated impedance becomes larger. This causes maloperation or operating time delay of the distance relay. A compensating algorithm estimates the correct secondary current from the severely distorted currents even when the measurement CTs are used. The correct current is estimated by adding the calculated magnetizing current to the measured secondary current. Test results show that the proposed distance relay can detect a fault without the operating time delay even when the secondary currents are extremely distorted because of use of measurement CTs.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.223-225
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• 2001

This paper discusses the dynamic test of distance relay on transmission line connected unified power flow controller(UPFC) using the real-time digital simulator(RTDS). Depending on operating conditions of UPFC, the trip characteristics of distance relay is influenced by the prefault conditions. In this paper, UPFC is established using the RTDS and then relay test is performed on real time.

• ETRI Journal
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• v.35 no.2
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• pp.336-339
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• 2013

To enhance the symbol error rate (SER) performance of the two-way relay channels with physical layer network coding, this letter proposes a relay selection scheme, in which the relay with the maximal minimum distance between different points in its constellation among all relays is selected to assist two-way transmissions. We give the closed-form expression of minimum distance for binary phase-shift keying and quadrature phase-shift keying. Additionally, we design a low-complexity method for higher-order modulations based on look-up tables. Simulation results show that the proposed scheme improves the SER performance for two-way relay networks.

• International journal of advanced smart convergence
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• v.6 no.3
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• pp.9-16
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• 2017

In this paper, we propose a new routing protocol for wireless sensor networks. This protocol improves energy consumption of ML-LEACH by reducing the transmission distance of member node via Relay Node. Since clusters of each Layer in ML-LEACH are randomly formed, the distance, between member node and cluster head may be longer than specific distance, distance threshold value. To improve this, we propose the new routing protocol using 2-Hop transmission via Relay Node depending on the transmission distance of the member node.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.346-353
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• 2008

This paper defines the concept of “protectability” for the performance evaluation of distance relay considering its sensitivity and selectivity. The paper starts from the probabilistic modeling of the errors, and based on this model, a detailed explanation of protectability calculation for each zone of the distance relay is presented. An effect of the Weighting Rate and the Measurement Deviation on the protectability evaluation is also given. By considering this effect, the optimization of relay setting can be realized. The proposed method is applied to a typical model system to show its effectiveness

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2196-2202
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• 2018

The conventional power system allowed only downstream power flow. Therefore, even if a fault occurs, only the forward current flow is considered. However, with the interest in distributed generation (DG), DGs such as Photovoltaic (PV), Wind Turbine (WT) are being connected to a power system. DGs have many advantages, but they also have disadvantage such as generation of reverse flow. Reverse flow can severely disrupt existing protection systems that only consider downstream power flow. The major problems that may arise from reverse power flow are blinding protection and sympathetic tripping. In order to solve such problems, the methods of installing a directional relay or a fault current limiter is proposed. However, this method is inconceivable because of the economics shortage. Therefore, in this paper, a distance relay installed in existing power system is used to solve the protection problem. Modeling of distance relay has been carried out using ElectroMagnetic Transients Program (EMTP), and it has been verified through simulations that the above problems can be solved by a distance relay.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.100-105
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• 2002

This paper represents impedance calculation of the distance relay using PSCAD/EMTDC software for transmission line involving the UPFC(Unified Power Flow Controller)device, which is the most vigorous component of FACTS. The presence of the UPFC significantly affects the line parameters of transmission system, which are also influenced by the distance relay setting. Moreover, depending on the UPFC location and its parameters, zones of setting the distance relay will be changed. The presence of the UPFC in the fault loop affects both voltage and current seen by relay. Therefore, the distance relay should be taken into account the variable injected voltage of the UPFC.