Demand response (DR) can play an important role when dealing with the increasing variability of renewables in power system. This study proposes a bi-level market model for wind-integrated electricity market, where the DR requirement is paired with the wind profile to deal with wind variability. At the upper level, an electricity market operator aims to minimise the day-ahead operation cost considering plausible wind generation scenarios. At the lower level, the DR exchange operator aims to maximise social welfare by trading aggregated DR among several aggregators. The solution at this level determines the optimal DR amount and price setting for each aggregator. The DR from the flexible loads is modelled from the end-users' perspective considering their willingness parameter. The market model is formulated as a bi-level optimisation problem using Lagrangian relaxation with Karush–Kuhn–Tucker optimality conditions. The effectiveness of the proposed scheme is demonstrated on sample 4-bus and IEEE 24-bus systems. Different scenarios such as high, medium and low levels of wind and DR are investigated. The high-wind low-DR scenario leads to minimum operation cost and is least inconvenient for end users as it sets the DR at a minimum level while keeping the higher levels of wind generation.

This study presents a method to establish the harmonic injection responsibility of either utility or consumer or both at the energy metering point. The method involves voltage and current harmonic components extraction using fast discrete stockwell transform (FDST). FDST overcomes the limitations of fast Fourier transform (FFT) and thus gives more accurate magnitude and phase angle information of harmonic components irrespective of noise effect. These harmonic components are utilised in phasor analysis to derive harmonic indices which arbitrates the responsible source for harmonic injection at the metering point. Energy billing is proposed based on evaluation of percentage harmonic injection responsibility which eradicates the drawback of conventional billing method. Several experimental cases are presented in order to validate the reliability, accuracy and effectiveness of the proposed technique for different supply and loading conditions. The proposed method is implemented over LabVIEW to show its feasibility in real-time scenario. The proposed energy billing scheme can be implemented in the existing energy meters and harmonic contribution share is easily attainable without any prior knowledge of network parameters.

With increased occurrences of a forest fire, the short-term reliability of power transmission lines needs to be re-evaluated considering the impact of forest fire on the ageing of transmission lines. How to include the impacts from a forest fire on line ageing in a comprehensive way becomes an important issue for the study of line failure probability. In this study, a method is proposed to evaluate the impact of forest fire on line ageing degree based on dynamic heat balance equation and Weibull distribution. The method will help maintenance staffs to assess the damage level of transmission lines. The method is tested by a contrast experiment and a case study with real meteorological data. Simulation results show that forest fire can greatly threaten the reliability of power transmission lines, while during this process flame characteristics, wind and load ratio could be the major factors that affect the line reliability. With the results obtained, this study also provides the system operator with valuable instructions on how to reduce the damages caused by fire to transmission lines.

This paper presents a methodology to analyse the influence of both atmospheric variations in time and space and the error in synchrophasor measurements to estimate conductor temperature along an overhead line. In this methodology, expressions to compute the error propagation in the computing of temperature because of measurement errors and load variations are proposed. The analysis begins by computing overhead line's thermal and mechanical parameters using simulations of load and atmospheric conditions. Having computed these parameters, values of resistance, inductance and capacitance of the overhead line modelled by means of a equivalent circuit are estimated, with the purpose of quantifying the sensibility of electrical parameters to changes in conductor temperature. Additionally, this analysis allows the identification of the temperature in each span along OHLs. Subsequently, the average conductor temperature is estimated using simulations of synchrophasors through the relationship between resistivity and temperature. This estimated temperature is compared with the temperature computed using atmospheric conditions to obtain the maximum error. This error is contrasted with the acceptable error margins. Thus, during the planning stage, this methodology can be used to assess PMU as a method of computing conductor temperature.

Here, based on wide-area measurement systems (WAMS), an adaptive tripping index (TI) is proposed for online prediction of tripping signals with respect to wide-area out-of-step (WAOOS) protection of synchronous generators. The proposed TI included two different equations consisting of a straight line for unstable inter-area oscillations and a sinusoidal line for WAOOS transient instability. For online identification of coherent generators with respect to inter-area oscillations, based on evaluating the correlation coefficients between generator behaviours, an index is proposed from which the global tripping signals (GTS) are calculated. The GTS consist of the rate of change of inter-area rotor angle oscillation between two oscillating areas in the centre of inertia frame. Actually, the proposed scheme is an adaptive and online index from which the critical inter-area angle is adjusted individually by evaluating GTS at each sampling time gathered from the WAMS data. The proposed strategy is implemented on an IEEE 39-bus test system and its performance is investigated by simulating typical scenarios during time-domain simulations. The results show the effectiveness of the proposed scheme for fast prediction of WAOOS protection in real-time environment.

The predictive calculation and wind effect on the ion flow environment of dc transmission line are evaluated by embedded short-term wind speed based ionised flow model. The wind has a major impact on the electric field and ion current density profiles. In the ionised flow model of embedded short-term wind speed, the short-term wind speed is calculated by using time series model and Kalman filter algorithm. The ionised field considering short-term wind speed is solved by finite-element method with acceleration technique and time-domain finite volume method. The algorithm is validated by the coaxial cylinder electrode configuration and practical bipolar dc transmission configuration. Computational results are made to provide a physical understanding of wind effect on the corona formation process. In the timescale of long-term prediction, the time evolution behaviour of ground-level ion current density and electric field with time-varying wind speed is estimated.

This study is centred around the economic dispatch (ED) problem of thermal generating units over a multi-time interval, to have generators collectively meet the load demand and network losses while minimising the system fuel costs. The underlying optimisation problem displays non-convexity due to the consideration of the valve point effect and ramping rates limit of generators. Additionally, the system operator by itself cannot determine the behaviours of generators since they are not willing to share their own cost functions and wish to make decisions by themselves. In view of these reasons, the authors provide a decentralised method based on gradient projection and piecewise approximation for the ED problem. It is shown that the proposed method converges to the global optimum when applying appropriate step-size parameters. The performance of the proposed method is demonstrated on the IEEE standard 5 and 10 units test systems, and via comparisons with the existed methods in the literature.

There is a general view that metal oxide surge arresters (MOSAs) are not in a position to offer an effective and consistent protection against very fast transient overvoltages (VFTOs). Quite predictably, it portrays MOSA in a poor light. The present sandwiched position of the arrester is mainly due to the combined effects of strong stray and block capacitances existing in an extra high voltage (EHV) network and the characteristic features of the incoming VFTOs. Contrary to this ‘popular view’, the theoretical performance assessment studies detailed here establish that a successful turnaround in the operation of MOSA under VFTOs is quite achievable. A detailed account of the electromagnetic transients programme (EMTP) and simulation studies performed is given; several oft-repeated, critical questions are also addressed. Essential measures to shore up the operation of MOSAs under VFTOs have also been brought to the fore. Finally, this study is a culmination of the ‘persistent efforts, brings a happy ending to a long pending issue’ and paves way for an effective and consistent protection to gas insulated substation (GIS) and its connected equipment against all kinds of life-threatening overvoltage surges that include VFTOs.

In recent years, abnormal heating of composite insulators has become a serious problem, especially in the coastal areas of southern China. In this paper, an improved multi-stress aging test for composite insulators was proposed based on the environment of the coastal areas in southern China, and 5000 h aging test was carried out. The test results showed that the wet flash-over voltage decreased linearly, while the hydrophobicity of the shed showed a nonlinear aging characteristics, whose change rate increased gradually. The multi-stress aging condition had little influence on shed hardness for the change of the shed hardness remained within 1%. The aged composite insulator showed significant temperature rise and the temperature rise concentrated on the high voltage end at high humidity, while it showed little temperature rise at low humidity. The dielectric loss of silicone rubber after moisture absorption was tested. It could effectively reflect the moisture absorption characteristics and the dielectric properties of silicone rubber after moisture absorption, and was closely related to the wet flash-over voltage and temperature rise of the composite insulator. The dielectric loss of silicone rubber after moisture absorption could be used as a new method to evaluate the operating state of composite insulators.

The variation characteristics of electrical variables and the variation pattern of oscillation centre in multi-source oscillation scenes are revealed, and a desynchronising centre positioning method is proposed. First, based on the multi-source oscillation model, the expressions of voltage and current in multi-source oscillation scenes are derived. And then, according to the definition of oscillation centre, the oscillation centre position function is constructed, as a quantitative description of the position of oscillation centre. On this basis, the impacts of power angle variation trend (oscillation mode), system operation mode variation and unequal emf amplitudes on the oscillation centre are analysed. Simulation results demonstrate that, the oscillation mode is the main factor that affects the drifting pattern of oscillation centre, system operation mode is the main factor that determines the drifting boundary of oscillation centre, and unequal emf amplitudes cause the oscillation centre to deviate towards the side with lower amplitude. Finally, according to the relationship between system emfs when the desynchronising centre appears, the desynchronising centre position function is derived, so that the position of desynchronising centre can be identified. Simulation results on Real Time Digital Simulator of multi-machine system verify the correctness of the analysis results.

This study presents an efficient method for modelling the proximity effect in complex conductor systems. This method is based on a discretisation partial element equivalent circuit (DPEEC) scheme in combination with artificial neural network (ANN). Circuit parameters of a conductor system are obtained with DPEEC at low frequency. ANN trained with the low-frequency parameters is employed to predict proximity effect at high frequencies. The proposed method significantly improves the calculation efficiency in both time and memory consuming. The method is validated by comparing with the result obtained by MoM-SO. Case studies of closely-spaced cables with different configurations are analysed. It is applied to evaluate the lightning current in typical cable installations. The comparison among different configurations reveals that the proximity effect leads to uneven current distribution in cables. Cable modelling without considering the proximity effect could lead to significant errors in transient current analysis.

Distribution system operators that seek operational excellence are supposed to design and implement capable processes throughout their value stream and assess how well their real services match the design specifications. Process capability analysis is a critical stage in systematic and sophisticated quality engineering approaches such as six sigma, which are based on quantitative studies. The capability of a distribution network to maintain the power quality and voltage level within an acceptable range is one of the most important aspects of design and utilisation of electricity distribution network. Capability analysis has been successfully used in the previous studies to assess the quality of conformance in the power distribution network. However, these studies were limited to a voltage level and other aspects of quality such as total harmonic distortion were neglected. In addition, parametric methods were not available to overcome the problem of multimodality in voltage distribution, especially in the presence of distributed generation. In the current study, for the first time, a parametric approach based on decomposing complex distributions to a few Gaussian distributions by artificial bee colony optimisation were used for evaluating the capability of the distribution network to maintain voltage level and power quality indices in predefined ranges.

Nowadays, more and more high-tech enterprises pay great attention to the enormous losses and risks caused by voltage sag. There is an urgent desire for voltage sag insurance. However, a feasible insurance mechanism is not yet available. Relationships among stakeholders (customers, insurance institution, power utility and government) are studied based on the analysis of insurability of voltage sag loss risk, and three possible voltage sag insurance mechanisms are proposed. Multi-objective two-stage decision-making method is introduced to combine the expectations of attributes of mechanisms for different stakeholders; the proposed method can simplify the fuzziness and the complexity of evaluating the process. This method combines the integrating scattered information into effective evaluation information, and it can reflect the recognition of different mechanisms by all the stakeholders objectively. This method can determine voltage sag insurance mechanisms, which are with the high feasibility to satisfy the requirement of all the stakeholders and to make sure all attributes are in good condition. Finally, the results of case studies for three high-tech customers located in the high-tech park have proved the correctness and rationality of the recommended insurance mechanism.

This study presents a methodology for enhancing the observability of interconnected power network with the incorporation of component reliability for incremental phasor measurement units (PMUs) placement. Initially, multiple optimal solutions for complete observability have been determined with the use of genetic algorithm. An overall system reliability index has been proposed for the selection of the most suitable solution among the determined solutions. Furthermore, the ranking of the buses for PMU placement has been performed using the proposed reliability observability criteria. An index determined by series–parallel combinations of different components of the network has been used for this purpose. To achieve effective multi-phasing of PMU placement analytical hierarchical process has been utilised. This strengthens the observability through most reliable buses during the initial phases. The proposed methodology is illustrated on IEEE 14-bus and eastern region Indian power grid 90-bus real system.