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Future multi-terminal dc networks are envisioned for the large-scale integration of renewable energy sources into today's power systems. An essential aspect for the reliable operation of these systems is the fast and selective dc-side fault handling and separation of faulted lines. The objective of this paper is the development and evaluation of a multi-terminal dc protection strategy based on fault-blocking converters (e.g., full-bridge based modular multi-level converters) and high-speed switches. Both a suitable fault control and a new high-speed switch design for a fast separation of faulted dc lines are elaborated. The novel concept is intended to reduce the requirements on the high-speed switches compared to dc circuit breakers and to ensure a fast restoration of the active power transmission capability, as well as the dc voltage. The fault-clearing strategy is analyzed using electromagnetic transient (EMT) simulations under variation of the fault location, type, and resistance. The investigations are carried out in a cable-based multi-terminal HVdc system with full-bridge modular multi-level converters in symmetrical monopole configuration. [ABSTRACT FROM AUTHOR]

This paper presents a new concept and approach for topology control and switching in distribution systems by extending the traditional circuit switching to laterals and single-phase loads. Voltage unbalance and other key performance indicators including voltage magnitudes, line loading, and energy losses are used to characterize and demonstrate the technical value of optimizing system topology on a per-phase basis in response to feeder conditions. The near-optimal per-phase topology control is defined as a series of hierarchical optimization problems. The proposed approach is applied to IEEE 13-bus and 123-bus test systems for demonstration, which included the impact of integrating electric vehicles (EVs) in the test circuit. It is concluded that the proposed approach can be effectively leveraged to improve voltage profiles with electric vehicles, the extent of which depends on the performance of the base case without EVs. [ABSTRACT FROM AUTHOR]

This paper shows that there is great potential for saving money when reconfiguring distribution systems at an optimal frequency. Studies are conducted on hourly, daily, weekly, monthly, and seasonal reconfiguration plans, based on the 8760 hourly loads of a year. Switches that actively participate in the reconfiguration process are first identified. These sectionalizers are substituted by smart (remotely controlled) switches. According to the results, two economic indices: total savings and return on investment are used to determine the optimal switching frequency. Numerical simulations are conducted on three distribution systems including one with 119 buses that is commonly used as a benchmark for reconfiguration of large-scale distribution systems. The results reveal that there exist large potential gains on frequent switching reconfiguration. Therefore, detailed studies must be carried out to determine the benefits of the dynamic reconfiguration for particular distribution systems. [ABSTRACT FROM AUTHOR]

Automation can significantly enhance substation reliability by speeding up service restoration. Although much research works has been done in reliability assessment of substation control systems, there are still several aspects that need to be considered in automated substation reliability evaluation. The impacts of automation system on substation reliability indices have not been comprehensively covered in the literature so far. This paper aims at presenting a comprehensive technique to quantitatively assess the reliability of the automated substations. The technique is based on the event tree methodology and the concepts of conditional probability technique. A step by step evaluation procedure is presented using a typical substation automation architecture known as simple star. The proposed technique is applied to some conventional substation configurations to examine the effectiveness of the technique and also to examine the level of reliability improvement achieved by automation. Furthermore, different sensitivity analyses have been carried out for both automatic switching action and a specific automated substation. The proposed strategy is easy to implement and suitable to analyze for an automated substation reliability with arbitrary automation architectures. Also, automated substation reliability assessment tools can be developed in detail, and can be catered to the specific needs of substation design. [ABSTRACT FROM AUTHOR]

In this paper, a new method is proposed that can be used to discriminate faults from switching transients. The method is primarily intended for use in systems where fast fault detection and fast fault clearing before the first peak of the fault current are required. An industrial system, in which high short-circuit power is desired but in which high short-circuit currents cannot be tolerated is an example of such a system. A phase-locked loop (PLL) is used to perform the discrimination. Computer simulations have been performed and it has been demonstrated that the output of the PLL is completely different for a fault compared to a switching transient. This difference can be used for discrimination between a fault and a switching transient. [ABSTRACT FROM AUTHOR]

This paper describes two new approaches for the determination of the direction of switched capacitor banks as well as an efficient technique for estimating the distance of switched capacitors from the monitoring location in distribution systems. At first, two new indices based on branch voltage and current changes immediately after the capacitor switching instant are proposed for determining the direction of switched capacitor banks. The wavelet transform is used to detect the exact instant of switching. Then, a new technique based on linear circuit theory is proposed to estimate the distance of the switched capacitor bank from the monitoring location using capacitor switching transient data. Simulation results show that the error of the estimated distance is acceptable. A combination of the approaches for direction finding and the technique for distance estimation provide a novel method for determining the location of switched capacitor banks in real distribution systems. The method is valid in all normal, back-to-back, and abnormal switching of wye- and delta-configured capacitor banks. Also, the size of the capacitor bank has no effect on method accuracy. The efficacy of the proposed method is validated by using the IEEE 13-bus and 34-bus distribution systems. [ABSTRACT FROM AUTHOR]