[en] Highlights: • Application of TSFCL to interconnect systems with different reliabilities is proposed. • TSFCL protects a grid by preventing detrimental effects from being delivered through the interconnection line. • A high-speed TSFCL with high impedance for transmission systems is required to be developed. - Abstract: Interconnection of power systems is one effective way to improve power supply reliability. However, differences in the reliability of each power system create a greater obstacle for the stable interconnection of power systems, as after interconnection a high-reliability system is affected by frequent faults in low reliability side systems. Several power system interconnection methods, such as the back-to-back method and the installation of either transformers or series reactors, have been investigated to counteract the damage caused by faults in the other neighboring systems. However, these methods are uneconomical and require complex operational management plans. In this work, a high-speed trigger-type superconducting fault current limiter (TSFCL) with large-impedance is proposed as a solution to maintain reliability and power quality when a high reliability power system is interconnected with a low reliability power system. Through analysis of the reliability index for the numerical examples obtained from a PSCAD/EMTDC simulator, a high-speed TSFCL with a large-impedance is confirmed to be effective for the interconnection between power systems with different reliabilities.

[en] The complex was obtained by reacting the macrocycle and AgNO₃ in MeOH/H₂O. The complex exhibits a 1D supramolecular polymer, where the chain is formed by hydrogen bonds between the two sets of pre-organized N-H groups of the macrocycle, nitrate ions and lattice water molecules. Space-filling and lattice diagrams of illustrating the supramolecular chain by hydrogen bonds are described in Figure 2. The coordination environment around the central Ag(II) ion is a square plane with four Ag-N bonds from the macrocycle. The Ag(II) ion sits on an inversion center. Tetraazamacrocycles and first synthesized by Kang et al., which are two of the 16 possible diastereoisomers of L have long been used for the preparation of many interesting metal complexes. Although the macrocycles and show similar coordination tendencies to metal ions and form corresponding metal complexes, the chemical and structural properties of metal complexes are greatly influenced by the stereochemistry of cyclohexane rings fused on the 14-membered tetraazamacro-cycle

[en] The operation of electric power network at any given time can be classified into one of the following states: normal, warning, alert, emergency and restoration, through reliability assessment. Typically, the classification into these states based on present method is useful for providing qualitative description of how reliably the network is being operated but lacks the quantitative valuation. In this paper we propose a new method for classifying operating states appropriate in Cost Based Pool (CBP) market in Korea. By taking the cost of control actions with respect to various plausible contingencies into consideration, the proposed method properly values the trade-off between technical reliability and economic efficiency. In applying the method the operational limits, such as maximum transfer capabilities and maximum voltages, are established at the planning stage. Established limits are then used to assess the reliability, and the control actions are applied by the system operator as needed at the operation stage. Several flowcharts are presented for showing how the proposed method is applied, and a case study is given for illustration purposes. It is shown that the proposed method properly incorporates the rational decision process by the system operator in detecting and responding to threats to system stability. In addition, it is shown that the classification by the proposed method is particularly useful for compensating network users participating in network control in the market environment. (author)

[en] The electricity markets with only few large firms are often vulnerable to less competitive behaviors than the desired. The presence of transmission constraints further restrict the competition among firms and provide more opportunities for firms to exercise market power. While it is generally acknowledged that the long-term contracts provide good measures for mitigating market power in the spot market (thus reducing undesired price spikes), it is not even more clear how effective these contracts are if the market is severely limited due to transmission constraints. In this paper, an analytical approach through finding a Nash equilibrium is presented to investigate the effects of long-term contracts on firms exercising market power in a bid-based pool with transmission constraints. Surprisingly the analysis in this paper shows that the presence of long-term contracts may result in the reduced expected social welfare. A straightforward consequence of the analysis presented in this paper will be helpful for the regulators in Korea to reconsider offering vesting contracts to generating companies in the near future. (author)

[en] Highlights: • Energy transition in Korea can be analyzed by simulating power market operations. • The phase out coal-fired power is the most effective option to reduce GHG emissions. • The simultaneous phase out nuclear and coal-fired power is not realistic in Korea. - Abstract: The Korean government announced a new energy transition policy that emphasizes phasing out nuclear and coal energy and increasing renewable energy sources. However, a lack of quantitative research has resulted in disagreements about the most suitable energy transition strategy for Korea. To evaluate the policy, we designed a quantitative analysis that simulates generation scheduling and settlement processes in the Korean power market. We then analyze the economic impacts, conflicts of interest, greenhouse gas (GHG) emissions, and the power system’s market price sensitivity to the price of imported liquefied natural gas (LNG) in four energy transition scenarios: i) the government’s new energy transition policy, ii) phase-out of nuclear energy, iii) phase-out of coal energy, and iv) simultaneous phase-out of nuclear and coal energy. Additionally, we evaluated the effects of coal taxation. Based on the power market simulation results, we conclude that phasing out nuclear energy with increasing taxation of coal, or only phasing out coal energy are two reasonable scenarios for energy transition in Korea. The simultaneous phase-out of nuclear and coal energy, which was originally pursued by the government, is inferior to the recommended scenarios in the aspects evaluated. Policymakers should consider these results when developing feasible energy transition scenarios.