Optimal compensating schemes for the secondary arc current limiting using neutral reactor for 1000 kV ultra-high voltage long parallel transmission lines in maintenance state are investigated in this study. For maintenance safety, the line in maintenance must be electrically isolated from the line in normal operation state. The influential factors such as transposition degree, arc resistance, load current and fault location are studied. Finally, the sensitivity of secondary arc current against the variation of neutral reactor value is investigated. Real-time digital simulator (RTDS) simulation tests have been carried out to verify the correctness and validity of the analysis presented in this study.

As the first stage of power system restoration after a blackout, an optimal black-start scheme is very important for speeding up the whole restoration procedure. Up to now, much research work has been done on generating or selecting an optimal black-start scheme by a single round of decision-making. However, less attention has been paid for improving the final decision-making results through a multiple-round decision-making procedure. In the group decision-making environment, decision-making results evaluated by different black-start experts may differ significantly with each other. Thus, the consistency of black-start decision-making results could be deemed as an important indicator in assessing the black-start group decision-making results. Given this background, an intuitionistic fuzzy distance-based method is presented to analyse the consistency of black-start group decision-making results. Moreover, the weights of black-start indices as well as the weights of decision-making experts are modified in order to optimise the consistency of black-start group decision-making results. Finally, an actual example is served for demonstrating the proposed method.

This study describes a support vector machine (SVM)-based technique for identifying loss-of-excitation (LOE) condition in synchronous generators from other disturbances such as external faults and power-swing conditions. In this new approach, only one zone of LOE is required and the time coordination is reduced significantly. The proposed method is compared with traditional two-zone impedance method. Several operating conditions within the generator capability are used to verify the generality of the SVM-based classifier. The proposed classifier identifies an LOE condition in all cases before the impedance enters the larger mho impedance zone. Faults and power-swing conditions are identified correctly, thereby preventing incorrect operation of the LOE impedance zone.

With ever increasing demand for electric energy, additional generation and associated transmission facilities has to be planned and executed. In order to augment existing transmission facilities, proper planning and selective decisions are to be made whereas keeping in mind the interests of several parties who are directly or indirectly involved. Common trend is to plan optimal generation expansion over the planning period in order to meet the projected demand with minimum cost capacity addition along with a pre-specified reliability margin. Generation expansion at certain locations need new transmission network which involves serious problems such as getting right of way, environmental clearance etc. In this study, an approach to the citing of additional generation facilities in a given system with minimum or no expansion in the transmission facility is attempted using the network connectivity and the concept of electrical distance for projected load demand. The proposed approach is suitable for large interconnected systems with multiple utilities. Sample illustration on real life system is presented in order to show how this approach improves the overall performance on the operation of the system with specified performance parameters.

This study proposes a novel approach for load modelling fulfilled in Guangdong Power Grid, Southern China. Dynamic load modelling lies on real-time data provided by load disturbances. These data can be acquired by power quality equipment fixed on each substation. This study introduces the approach to data processing and load modelling during asymmetric disturbance to solve the problems of insufficient inartificial disturbance data. In order to improve the global optimisation capability and identification efficiency in multi-dimensional function, an improved clone selection algorithm is proposed, which includes adaptive-adjust Gaussian mutation operators and the directional evolution mechanism, and also using the character of parameters independence between induction motor model and ZIP model referring to the third-order induction-motor paralleling ZIP model in BPA. The results of practical load modelling prove that the proposed algorithm has great effects on improving model precision and adaptability. Finally, the influences on power angle, frequency, voltage and power between dynamic load model and ZIP are discussed.

This study introduces a fast locating algorithm for a switched shunt capacitor based on the slopes of the voltage/current space vectors at monitoring points of a power system. Compared with the other suggested slope-based methods, such as signal-processing and filter-based methods, the proposed algorithm herein offers a robuster and more reliable locating method because of using the information of all three phases, whereas other methods separately process individual phase signals. The method is training free and established based on algebraic calculations with a simple realisation algorithm, which is independent of the power system dynamics and parameters. The proposed method is analytically investigated and then verified based on the time-domain simulation of two study systems. The study systems cover various capacitor-switching scenarios, harmonic effects and measurement noise and power system dynamics including dynamics of rotating machines and power electronic converters.

Setting the pickup current and slope of differential relays of power transformer protection is a well-known compromise. It has been the focus of study to improve both the security and sensitivity of transformer differential protection recently. However, it is difficult to achieve a high degree of security and sensitivity at the same time by conventional percentage restraint differential criteria based on a fixed predetermined characteristic curve. Therefore a novel adaptive protection criterion is proposed in this study, which can self-regulate the parameters of percentage differential characteristic (e.g. pickup current, restraint coefficient and restraint current at the knee point of the slope characteristic) on the basis of operating conditions of power transformers. The test results show that the proposed scheme provides a high operating sensitivity on internal faults, while retaining higher security on all external faults. Furthermore, because of self-regulation of the setting values of relays, it is more convenient for engineers in the field who only need to give the upper and lower limits but not the exact value of the settings of protective relay.

Substation circuit breakers and other equipment are sized to withstand the maximum anticipated short-circuit currents. Although the short-circuit analysis used to design a substation takes into account the expected expansion of the network, over time the maximum short-circuit current, especially for certain operating conditions, can exceed the circuit breaker ratings. As upgrading the equipment is expensive, the life of the present equipment can be extended if these violation conditions can be identified in real time and operational actions taken to mitigate them. In this study, the authors present a method for on-line short-circuit analysis and a method for determining preventive action using transmission line switching.

This study presents a novel stochastic multi-objective model for precise scheduling of energy and reserve services in day-ahead markets. This model is based on a security-constrained market clearing with an emphasis on preservation of system frequency. A frequency index that is derived from the total system frequency profile during post-contingency intervals has been defined as an extra objective function to control system frequency after the occurrence of a contingency. The model is capable of scheduling the tertiary regulation interval through appropriate generators’ reference power setting instructions made by the ISO based on participants’ bids for energy and reserve services. The reference power settings are obtained by an optimisation model and can be performed directly by the speed changers. The load dependency on frequency has also been analysed in the proposed model. This approach could be used by ISOs to make a trade-off concurrently between system frequency profile and total operating cost to operate the power system securely in an economically efficient manner. The developed multi-objective programming is analysed through two case studies; a three-bus system scheduled over 1 h and the IEEE 24-bus reliability test system over 24 h, solved by means of mixed-integer linear programming methods.

Till today, flashover because of pollution of insulators of overhead transmission lines (OHTL) is a major source of trouble in the electrical power transmission system. The importance of this problem can be assessed from fault statistics of high-voltage transmission lines. In Egypt, for example, about 82% of the total faults of transmission and distribution OHTL  are because of pollution. This study deals with laboratory tests, which have been carried out on polluted insulators of the OHTL that simulate desert environments. In this study, the effect of the variation of conductivity of the polluted layer by means of equivalent salt deposit density on flashover voltage (FOV) is investigated. The effect of variation of conductivity of the polluted, layer along the time required by the procedure needed to form dew, on FOV is also studied. This study is useful for indicating the worst period after the formation of dew, where the probability of flashover is increased.