• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.280-281
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• 2011

Special Protection Scheme(SPS) that operates scenarios about faults beyond the normally protective action is wide system protection technology for the purpose of wide areas protection. Therefore, the SPS focuses on the improvement of the power supply capability by protecting the system rather than protecting the system equipments. Since the SPS requires emergency operation, the operation schedule is set up in advance by analyzing various scenarios. Since the SPS's action scheme uses generator tripping and is a classical method it is presently the most powerful one. However, as the setting of SPS is set to the most severe disturbance, the scheme tends to trip more generators than required to prevent fault propagation. It is highly likely that tripping generator units to prevent fault propagation would result in difficulty of system management and possibility of load shedding. Accordingly, it is desirable that generators are connected to the system within the range that ensures system stability and intelligent SPS is currently under development to solve the problem being stated. In this paper, as a part of developing the intelligent SPS, application of the fast-valving and braking resistor scheme to the generators is being proposed and analysed to reduce the number of tripped generators.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.1-7
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• 2019

Due to the highly concentrated power plants integrated through the limited transmission lines in Korea, a Special Protection System(SPS) has been applied to stabilize the power systems by instantly tripping the pre-determined generators in a large-scaled power plant when a fault occurs on the drawing transmission lines. Moreover, power outputs of those generators are constrained to avoid any activation of Under Frequency Load Shedding(UFLS) even after those generators are tripped by SPS action. For this, this paper proposes a method for calculating the required capacity of Energy Storage System(ESS) expected to relieve the operating constraints to generators using its fast response for controlling power system frequency. The proposed method uses the generator acceleration energy to derive the stable condition during the SPS action. In addition, its effectiveness is verified by the case studies adopting actual SPS operations in Korean power systems.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.476-484
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• 2009

This paper deals with improvements to the special protection schemes (SPS) which have been applied to the low probability and high impact contingencies in the Korea Electric Power Corporation (KEPCO) system since 2004. Among them, the SPS for voltage instability in the Seoul metropolitan area is considered in this paper, and is a form of event-based undervoltage load shedding with a single-step scheme. Simulation results based upon a recent event that occurred on 765kV lines show that the current setting values of the SPS have to be revised and enhanced. In addition, by applying response-based multi-step undervoltage load shedding (UVLS) schemes to severe contingencies in the system, more effective results than those of the existing single-step SPS can be obtained. Centralized and distributed UVLS schemes are considered in the simulation. ULTC-based load recovery models and over excitation limiters (OXL) for the KEPCO system are also included in the long-term voltage instability studies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.411-417
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• 2014

Special Protection Scheme(SPS) for generator tripping action is an emergency control tool that secures the power system stability by instantly tripping the pre-determined number of generators to avoid the acceleration of the remaining generators in a large-scaled power plants when a fault occurs on the drawing transmission lines. However, since the existing operating conditions of SPS are set based on a peak demand, SPS could trip more generators than required if it is activated during the off-peak demand period. For this, this paper proposes the algorithm for setting the operating conditions of SPS through the online stability evaluation with the periodically updated operating conditions of power systems. The proposed algorithm adopts COA for the accuracy and speed of the stability evaluation, and can reduce the number of tripping generators by SPS during the off-peak demand period. This results in reducing the loss of profit caused by a fault on power systems.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.105-113
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• 2018

This paper proposes pre-analysis on planning of high-voltage direct current (HVDC) transmission system applied to Korea electric power grid. HVDC transmission system for interface lines has been considered as alternative solution for high-voltage AC transmission line in South Korea since constructing new high-voltage AC transmission lines is challenging due to political, environmental and social acceptance problems. However, the installation of HVDC transmission system as interface line in AC grid must be examined carefully. Thus, this paper suggests three scenarios to examine the influences of the installation of HVDC transmission system in AC grid. The power flow and contingency analyses are carried out for the proposed scenarios. Power reserves in metro area are also evaluated. And then the transient stability analysis focusing on special protection scheme (SPS) operations is analyzed when critical lines, which are HVDC lines or high voltage AC lines, are tripped. The latest generic model of HVDC system is considered for evaluating the impacts of the SPS operations for introducing HVDC system in the AC grid. The analyses of proposed scenarios are evaluated by electromechanical simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.6
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• pp.845-851
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• 2015

Load shedding is a last measure to avoid nationwide cascading collapses of power system by removing the pre-determined amount of loads from the main grid. In Korea, SPS(Special Protection System) is prepared to keep the power system stability from the extreme contingency of the critical transmission line losses. Among them, we need to pay attention to 765kV T/L’s because they have great influence on the total system stability. According to the present SPS operating guide, the total loads of 1,500MW should be removed through 2 step under-voltage load shedding(UVLS) scheme in case of 765kV T/L’s contingencies. However, it is not clear to defined how to determine the typical load reduction amounts for each case. This paper proposes a method to estimate appropriate amounts of load shed for 765kV T/L’s contingencies by analyzing the relevant national and international standards.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1554-1560
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• 2017

Prepare a lose of 765kV transmission route in power system operation condition, there are some Special Protection Scheme(SPS)s in Korean power system. These SPS can make some preselected generators are tripped to avoid generator overspeed. Because of many of the new large power plants are installed to existing power generation sites due to the siting problem, the number of generator tripped by SPS should be increased. But that can be a cause of system frequency change under the Under Frequency Relay(UFR) 1st pickup level 59.0Hz. Therefore generation constraint should be considered until new transmission lines are installed. In this paper, we propose the ESS application for generation constraint mitigation by frequency damping control of ESS. To analysis an effect of ESS application, we use PSS/E dynamic simulation tool, CBEST model and controller model. The proposed ESS application is applied to the empirical Korean power system.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.274-276
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• 2002

긴급보호제어시스템(SPS, Special Protection System)은 일반적인 보호동작 범위를 벗어난 외란에 대해서 계통 전지역의 보호를 목적으로 하는 광역시스템 보호기술이다. 따라서 SPS는 외란 시에 계통 장비의 보호보다는 계통을 보호함으로써 전력 공급능력 향상에 주안점을 두게 된다. SPS는 자주 동작하지 않고 평소에는 대기 상태로 있으며, 긴급한 동작이 요구되기 때문에 많은 경우에 그 동작이 미리 결정되어 있다. SPS는 입력변수나 전력계통에의 영향에 따라 분류할 수 있는데, 입력변수에 따라서는 계통 응답에 기초한 SPS와 사고에 기초한 SPS로 나눌 수 있다. 발전기 탈락, 부하 차단이 SPS의 주요 보호 동작이며 이 외에 가스터빈이나 양수발전기 기동, AGC 제어, HVDC 고속전력변환, 분로기기의 자동스위칭 등의 제어 동작이 있다. 우리나라의 경우에는 주로 동기탈조 방지를 위한 발전기 탈락의 동작을 하는 SPS가 설치, 운전되고 있다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1733-1740
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• 2010

KPX(Korea Power Exchange) predicts that summer peak load will be 70,700MW and system overload will be 150% from contingency analysis. This paper presents a method to operate power system at 2010 summer peak. about equipment variation, power system variation, analysis results of voltage stability, and the method to relief overload by comparing 2009 and 2010. Especially, transmission constraints to prevent global contingency in Korea power system and the role of SPS(Special Protection System) to prevent voltage collapse when fault occurs are introduced.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.87-88
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• 2008

현재 전국적으로 많은 곳에 SPS(고장파급방지장치)가 설치되어 운영중에 있으며 대부분은 345kV이상 대단위 전원단지 인근에 설치되어 있으나 강원지역의 경우는 154kV 계통에 다수가 설치되어 운전중에 있다. 강원지역은 지역적 특성으로 인해 장거리 송전선로가 많으며 전원단이 원거리에 위치하여 고장시 전압불안정에 의한 계통붕괴의 위험성이 타 지역보다 높다. 특히 하계에 비해 난방부하 및 심야전력의 영향으로 최대부하가 대폭 증가하는 동계의 경우 이러한 특성이 더욱 두드러지는데 2007년 동계피크시 부하실적 및 역률을 기준으로 부하특성 및 부하역율 변동에 따른 계통영향을 분석하여 기 설치 운영중인 SPS 적용의 타당성 및 유지여부에 대한 판단 및 SPS 적용 개선(안)을 제시하였다.