• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.9
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• pp.62-68
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• 2011

Power system needs to sustain high reliability due to its complexity and security. The reliability prediction method is usually based on independent failure. However, in practice, the Common Cause Failures(CCF) and Cascading failure occur to the facilities in power system as well as independent failures in many cases. The CCF and Cascading failure turn out the system collapse seriously in a wide range. Therefore to improve the reliability of the power system practically, it is required that the analysis is conducted by using the CCF and Cascading failure. This paper describes the CCF and Cascading failure modeling combined with independent failure. The incorporated model of independent failure, CCF and cascading failure is proposed and analyzed, and it is applied to the distribution power system in order to examine this method.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.121-130
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• 2021

Cascading failure is the main cause of large blackouts in electrical power systems; this paper analyzes a cascading failure in Hanbit nuclear power plant unit two (2) caused by a circuit breaker (CB) operation failure. This malfunction has been expanded to the loss of offsite power (LOOP). In this study, current practices are reviewed and then the methodologies of how to prevent cascading failures in protection power systems are introduced. An overview on the implementation of IEC61850 GOOSE messaging-based zone selective interlocking (ZSI) scheme as key solution is proposed. In consideration of ZSI blocking time, all influencing factors such as circuit breaker opening time, relay I/O response time and messages travelling time in the communication network should be taken into account. The purpose of this paper is to elaborate on the effect of cascading failure in NPP electrical power protection system and propose preventive actions for this failures. Finally, the expected advantages and challenges are elaborated.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.1
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• pp.13-17
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• 2018

According to the recent blackouts, large blackouts can be described by cascading outages. Cascading outage is defined by sequential outages from an initial disturbance. Sequential and probabilistic approach are necessary to minimize the blackout damage caused by cascading outages. In addition, conventional cascading outage analysis models are computationally complex and have time constraints, it is necessary to develop the new analytical techniques. In this paper, we propose the advance visualization model for probabilistic analysis of cascading failure risks. We introduce the visualization model for identifying size of cascading and potential outages and estimate the propagation rate of sequential outage simulation. The proposed model is applied to Korean power systems.

• Korean Journal of Artificial Intelligence
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• v.11 no.2
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• pp.1-6
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• 2023

This paper presents a comprehensive scheme for assessing the importance of multiple microgrids (MGs) network that includes distributed energy resources (DERs), renewable energy systems (RESs), and energy storage system (ESS) facilities. Due to the uncertainty of severe weather, large-scale cascading failures are inevitable in energy networks. making the assessment of the structural vulnerability of the energy network an attractive research theme. This attention has led to the identification of the importance of measuring energy nodes. In multiple MG networks, the energy nodes are regarded as one MG. This paper presents a modified PageRank algorithm to assess the importance of MGs that include multiple DERs and ESS. With the importance rank order list of the multiple MG networks, the core MG (or node) of power production and consumption can be identified. Identifying such an MG is useful in preventing cascading failures by distributing the concentration on the core node, while increasing the effective link connection of the energy flow and energy trade. This scheme can be applied to identify the most profitable MG in the energy trade market so that the deployment operation of the MG connection can be decided to increase the effectiveness of energy usages. By identifying the important MG nodes in the network, it can help improve the resilience and robustness of the power grid system against large-scale cascading failures and other unexpected events. The proposed algorithm can point out which MG node is important in the MGs power grid network and thus, it could prevent the cascading failure by distributing the important MG node's role to other MG nodes.

• Korean Journal of Construction Engineering and Management
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• v.19 no.3
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• pp.33-42
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• 2018

In the aftermath of an earthquake, seismic-damaged infrastructure systems loss estimation is the first step for the disaster response. However, lifeline systems' ability to supply service can be volatile by external factors such as disturbances of nearby facilities, and not by own physical issue. Thus, this research develops the bayesian model for probabilistic inference on common-cause and cascading failure of seismic-damaged lifeline systems. In addition, the authors present network robustness estimation metrics in the context of failure propagation. In order to quantify the functional loss and observe the effect of the mitigation plan, power and water supply system in Daegu-Gyeongbuk in South Korea is selected as case network. The simulation results show that reduction of cascading failure probability allows withstanding the external disruptions from a perspective of the robustness improvement. This research enhances the comprehensive understanding of how a single failure propagates to whole lifeline system performance and affected region after an earthquake.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.1
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• pp.21-26
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• 2017

Failure of high-voltage transmission line, which is responsible for large-scale power transmission, can be reason for system voltage instability. There are many methods to prevent voltage instability like adjustment of equipment, the generator voltage setting, and load shedding. Among them, the load shedding, have a problem of economic loss and cascading effect to power system. Therefore, the execution of load shedding, amount and timing is very important. Conventionally, the load shedding setting is decided by the preformed simulation. Now, it is possible to monitor the power system in real time by the appearance of PMU(Phasor Measurement Unit). By this reason, some of research is performed about decentralized load shedding. The characteristics of the load can impact to amount and timing of decentralized load shedding. Especially, it is necessary to consider the influence of the induction motor loads. This paper review recent topic about under voltage load shedding and compare with decentralized load shedding scheme with conventional load shedding scheme. And simulations show the effectiveness of proposed method in resolving the delayed voltage recovery in the Korean Power System.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.184-186
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• 2003

Power systems must be operated within limits that will ensure adequate generation and transmission capacity to avoid cascading. In developing a set of operations limits, it is important to do so within a general framework in order to ensure that the operating objectives are met. In the this regard, when the system experiences a generation-load imbalance, the principles of sound operation will be maintained by bringing under control an unscheduled power flow condition as quickly as possible. This paper presents load shedding application which responds both to frequency and to rate of change of frequency. Its application is in the operating situation of load suddenly in excess of generation, either because of generator or other equipment failure. A scheme which is able to utilize rate of change of frequency as well as frequency itself is an improvement over existing scheme.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.60-67
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• 2018

The presence of induction motor loads in a power system may cause the phenomenon of delayed voltage recovery after the occurrence of a severe fault. A high proportion of induction motor loads in the power system can be a significant influence on the voltage stability of the system. This problem referred to as FIDVR(Fault Induced Delayed Voltage Recovery) is commonly caused by stall of small HVAC unit(Heating, Ventilation, and Air Conditioner) after transmission or distribution system failure. This delayed voltage recovery arises from the dynamic characteristics associated with the kinetic energy of the induction motor load. This paper proposes the UVLS (Under Voltage Load Shedding) control strategy for dealing with FIDVR. UVLS based schemes prevent voltage instability by shedding the load and can help avoid major economic losses due to wide-ranging cascading outages. This paper review recent topic about under voltage load shedding and compare decentralized load shedding scheme with conventional load shedding scheme. The load shedding strategy is applied to an actual system in order to verify the proposed FIDVR mitigation solution. Simulations demonstrate the effectiveness of the proposed method in resolving the problem of delayed voltage recovery in the Korean Power System.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.441-448
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• 2022

In the distribution system, there are multiple power protection systems such as circuit breakers at substations, and reclosers, minimum circuit ampacities, fault interrupters on distribution lines. They are widely used to prevent partial outages, cascading power failure or blackout so that other healthy systems could maintain the integrity in case of the instant fault or permanent failure on the power lines. However, when a fault happens, it could cause a major black out due to the lack of the protection cooperation between the protection relay of the circuit breaker at a substation and a protection system on the distribution lines. To achieve the power system integrity better, it is required to develop the circuit breaker which can be operational within 1 cycle(16ms). In this study, the high speed circuit breaker which is filled up with eco-friendly gas is developed. This equipment achieved an excellent test results based on IEC 62271-111 standard. It is respected that this equipment would contribute to prevent the wide area blackout by isolating a fault area quicker and faster.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.191-200
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• 2020

Tracked military vehicles are operated under harsher conditions and climates than ordinary vehicles, and the components require high degrees of reliability and durability. A diesel engine is the main power generator, and when the vehicle breaks down, there is a high possibility of causing a large-scale accident. Therefore, analyzing the cause of engine failure can be important for preventing similar cases that may occur. In this study, we clarified the mechanism of engine failure according to an overhaul test, hardness measurement, and an analysis of the fracture surface. The overhaul test confirmed that a bolt was separated from the connecting rod (number 4). In addition, the hardness measurement results of the connecting rod bolt conformed to the standard, and it was found that the bolt fracture was ductile fracture through an analysis of the fracture surface. Based on the results, it was concluded that damage to a diesel engine of a tracked military vehicle was caused by separating and damage caused by loosening of the connecting rod bolts, resulting in cascading damage. The results of the study could be used as reference examples and could be useful for another study on engine failure analysis.