• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1053-1058
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• 2010

A large modern wind farm should satisfy the requirements for a grid and accomplish the optimization of the wind farm system. The wind farm intertie protection system should consider a Fault Ride-Through (FRT) requirement for more reliable protection. The wind farm should keep connected to the grid in the case of a grid fault whilst it should be isolated for an intertie fault. This paper proposes a distance relaying algorithm suitable for wind farm intertie protection considering the FRT requirement. The proposed algorithm estimates the impedance based on a differential equation method because the frequency of the voltage and current deviates the nominal frequency. The algorithm extends the reach of Zone 1 up to 100 % of the length of the intertie to implement the FRT requirement. To discriminate an intertie fault from a grid fault, the algorithm uses a voltage blocking scheme because the magnitude of the voltage at the relaying point for an intertie fault becomes less than that for a grid fault. The performance of the algorithm is verified using a PSCAD/EMTDC simulator under various fault conditions. The algorithm can discriminate successfully the intertie fault from grid fault and thus helps to implement the FRT requirement of a wind farm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2167-2172
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• 2008

A large scale embedded generator or a micro-grid is usually interconnected to the grid through the dedicated line. Immediately after the removal of the grid supply, it must be disconnected and remain disconnected until the normal grid supplies are restored. This paper proposes an islanding detection algorithm based on complex power at the intertie. Complex power at the intertie delivered to the grid has a value depending on power flow during normal operation. When loss of mains occurs, complex power at the intertie moves to a value depending on the parameters of the dedicated line. The performance of the proposed algorithm was investigated under various operating and fault conditions. The proposed algorithm can detect an islanding operation even if no power is exchanged prior to loss of mains and discriminate the fault condition from islanding.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.442_443
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• 2009

A large wind farm should satisfy the requirements for a grid and accomplish the optimization of the wind farm system. In that point of view, the wind farm intertie protection system, which must consider the Fault Ride-Through (FRT) requirement for more reliable protection, should be improved. This paper proposes a modified distance relay suitable for protection of a wind farm intertie considering a FRT requirement. The frequency change is used to discriminate the intertie fault from a outside zone fault. The performance of the proposed algorithm is verified using a PSCAD/EMTDC simulator.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.484_485
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• 2009

Power output of a wind farm fluctuates throughout a day. This affect a distance relay for wind farm intertie protection because a voltage of a relaying point varies due to fluctuating output of a wind farm. This paper describes the analysis of the response of a distance relay for intertie protection when the power output of a wind farm increases. A series of single phase to ground faults were also simulated and analyzed with PSCAD/EMTDC generated data.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.91-92
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• 2011

Beat is a phenomenon, where the magnitudes and frequencies of the voltage and the current fluctuate. This paper describes a quantitative analysis of the beat phenomenon of a wind farm using the envelope of a current during intertie/grid fault conditions. In this paper, the ratio of the crest to the trough of the envelope curve and the time interval between adjacent troughs are defined and used to evaluate the beat phenomenon quantitatively. Beat phenomena under various fault and wind conditions are analyzed. The proposed quantitative analysis seems simple but effective in the more understanding of beat phenomenon of a wind farm, and thus can be used as a basis for operation and/or protection of an intertie.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.234-236
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• 2002

The Co-Gen System which maximize energy efficiency was installed at the industrial plants at the initial stage. However Small Scale Co-Gen System was expanded even to the general end-users such as housing and building owing to ESCO business recently. For this SSC, inter-connected operation to the utility is desirable due to voltage and frequency fluctuation following to unbalance between power output and load. Then voltage unbalance with utility system, frequency, increase of short circuit capacity, reclosing, and ALTS etc. should be fully considered for the inter-connected operation. Voltage variation, protection coordination, Co-Generators single running, and short circuit capacity should also be solved. To research the method and solve the problems through the field test and application, we study individual customers Co-Gen System as a case study.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.166-168
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• 2001

Generation by the privately owned generators, which are normally operated has occupied about 10% of total generation. Recently the small co-generation employed gas engine has been introduced and attracted public interest. For privately owned generator to be paralleled Utilities, a customer complies with Generator Parallel Operation Guideline set by Utilities and installs related protective relays. But the guideline is not specified to small co-generation, only provides parallel operation of privately owned generator. So applying this guideline, initial investment can be too high comparing to total co-generation cost. Besides there is no specified guide about ALTS, which arises asynchronous problem. In this paper we analyzed guideline and technical problem when small co-generation is paralleled. And additionally needed researching area to improve distribution of small co-generation is discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.5
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• pp.664-668
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• 2012

This paper presents the operation strategy of KEPCO(Korea Electric Power COporation) ${\pm}80kV$ 60MW Bipole HVDC system that will be applied between Guemak C/S(converter station) and Hanlim C/S in Jeju island. Unlike intertie HVDC system, this system is located in AC power grid inside. Therefore, the enhancement of system security related with line flow and bus voltages can be major operation strategy. In this paper, in particular, the optimal operation algorithm in the abnormal(not steady state) power system is presented and simulated.

• Proceedings of the KIEE Conference
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• 2004.05b
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• pp.227-230
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• 2004

The Co-Gen System which maximize energy efficiency was installed at the industrial plants at the initial stage. However Small Scale Co-Gen System was expanded even to the general end-users such as housing and building owing to ESCO business recently. For this SSC, inter-connected operation to the utility is desirable due to voltage and frequency fluctuation following to unbalance between power output and load. Then voltage unbalance with utility system, frequency, increase of short circuit capacity, reclosing, and ALTS etc. should be fully considered for the inter-connected operation. Voltage variation, protection coordination, Co-Generators single running, and short circuit capacity should also be solved. For Con-Gen users, the several protection relays are recommended to install at the user's main incoming panel by the guide lines and/or instructions of the interconnected utility Then user's main CB(Circuit Breaker) have the chance to be tripped by some of this recommended relays and users have to undergo the unexpected blackout. So the circuit breaker trip schemes targeted to trip with these protection relays are reconsidered and the study result is hereunder proposed.