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In the process of determination of breakpoints for overcurrent relays (OCR), different sets with equal number of OCRs can be selected as minimum breakpoint set (MBPS). Therefore, determination of the most appropriate MBPS is an issue which must be considered. This paper proposes a prioritization between different MBPSs based on the sum of operating times of OCRs. In this case, a set which results the minimum sum of operating times is selected as the appropriate MBPS. For this purpose, the proposed method combines two problems: determination of MBPS and coordination of OCRs, and is expressed in mixed‐integer linear programming (MILP) form. Also, a modified depth‐first search (DFS) algorithm is applied to determine the OCRs contained loops of studied networks. It is shown that the proposed method has the capability to be combined with previous defined expert rules in this field in order to consider the network conditions in the process of determination of optimal breakpoint set (OBPS). The proposed method has been implemented on various size networks, and the results show the effectiveness of proposed method in determining breakpoint set with the least number in first priority and minimum operating times of relays in second priority. [ABSTRACT FROM AUTHOR]

This study presents a new method to protect the radial feeders on marine vessels. The proposed protection method is effective against phase–phase (PP) faults and is based on evaluation of the ratio between the negative sequence and positive sequence of the fault currents. It is shown that the magnitude of the introduced ratio increases significantly during the PP fault, hence indicating the fault presence in an electric network. Here, the theoretical background of the new method of protection is firstly discussed, based on which the new protection algorithm is described afterwards. The proposed algorithm is implemented in a programmable digital relay embedded in a hardware‐in‐the‐loop (HIL) test set‐up that emulates a typical maritime feeder using a real‐time digital simulator. The HIL set‐up allows testing of the new protection method under a wide range of faults and network conditions and the experimental results demonstrate its effectiveness in all scenarios conducted. The proposed protection method offers a solution to the protection challenges associated with variability of the short‐circuit currents in radial feeders, advancing in this way the traditional mean of protection in maritime feeders, represented by overcurrent relays. [ABSTRACT FROM AUTHOR]

This study focuses on developing an integrated transmission and distribution framework that couples the two sub‐systems together with due consideration to conventional demand flexibility. The proposed framework ensures accurate representation of the system resources and the network conditions when modelling the distribution system in the transmission optimal power flow and vice‐versa. It is further used to develop an accurate pricing mechanism (distribution‐based location marginal pricing), which is reflective of the moment‐to‐moment costs of generating and delivering electrical energy, for the distribution system. By accurately modelling the two sub‐systems, the authors can improve the economic efficiency and the system reliability, as the price sensitive resources can be controlled to behave in a way that benefits the power system as a whole. [ABSTRACT FROM AUTHOR]

Energisation of large power transformers may cause significant voltage dips, of which the severity largely depends on a number of parameters, including circuit breaker closing time, transformer core residual flux and core saturation characteristic, and network conditions. Since most of the parameters are of stochastic nature, Monte Carlo simulation was conducted in this study to stochastically assess the voltage dips caused by transformer energisation in a 400 kV grid, using a network model developed and validated against field measurements. A dip frequency pattern was identified over 1000 stochastic runs and it was found to be sensitive to residual flux distribution but insensitive to closing offset time distribution. The probability of reaching the worst case dip magnitude (estimated under the commonly agreed worst energisation condition) was found to be lower than 0.5%; about 80% of the dips are likely to be with magnitudes lower than 0.6 pu of the worst case. Nevertheless, there are dips with magnitudes exceeding the worst case dip magnitude, indicating the inadequacy of deterministic assessment approach by using the commonly agreed worst energisation condition. [ABSTRACT FROM AUTHOR]