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Underground cables will be applied more often within new connections of the extra-high-voltage (EHV) transmission network. Since EHV underground cables are a relatively new technology, not much is known about their behavior in large transmission networks. Underground cable connections (consisting of cables, joints, and terminations) are, in general, less reliable than traditional overhead lines, mainly because of their much longer repair time. This can negatively influence the reliability of the transmission network as well. It is therefore of interest to study the reliability of underground cable connections in detail. This paper concentrates on the reliability of EHV underground cable and overhead line connections. Based on actual failure statistics of individual components, the reliability of a connection is analyzed, and which factors are of influence and what measures can be taken to improve the reliability are studied. An optimized cable repair process and a configuration with additional disconnectors are two solutions.

Transients from lightning strikes can enter underground cables at overhead line to power cable transitions. Possible overvoltages on these surges at cross-bonding connections of the cable screens are of major concern. A model is developed for modelling overvoltages from transient signal propagation through a combined cross-bonding cable and box. This model is applied to the first Dutch 400 kV cable connection. Such model incorporates model parameters whose values depend on design details of the cross-bonding box. The values for these model parameters are extracted from the measured transmission and reflection signal on steep pulses injected into the actual cross-bonding box configuration. The model combines transmission line description for the cross-bonding cables with mainly inductive behaviour of the cross-bonding box. The obtained results are verified by measurements. The model is applied to investigate overvoltages induced at the cross-bonding cable and box on 1.2/50 µs impulse voltage injection representing a lightning impulse voltage applied to the core conductor of the cross-bonding cable. Furthermore, the effectiveness of surge arresters to reduce overvoltages at the cross-bonding cable screen is demonstrated by simulations with this model in PSCAD.

Current and future developments in the power system industry demand fast power flow solvers for larger power flow problems. The established methods are no longer viable for such problems, as they are not scalable in the problem size. In this paper, the use of Newton-Krylov power flow methods is proposed, and a multitude of preconditioning techniques for such methods are discussed and compared. It is shown that incomplete factorizations can perform very well as preconditioner, resulting in a solver that scales in the problem size. It is further shown that using a preconditioned inner-outer Krylov method has no significant advantage over applying the preconditioner directly to the outer iterations. Finally, algebraic multigrid is demonstrated as a preconditioner for Newton-Krylov power flow and argued to be the method of choice in some scenarios.

Service interruptions have a significant impact on society and therefore the main objective of power system planning and operation is to ensure that they do not happen. Because voltage instability is one of the dynamic phenomena that may result in a system-wide blackout, this type of stability problem has been an important research topic for many years. Grid developments, like the increase of Renewable and Distributed Generation (RDG) and the impact of deregulation, in combination with the steadily increasing electricity demand, will have its impact on the vulnerability of the power system to voltage stability problems. On the other hand, developments in power system monitoring and control such as the use of accurate Phasor Measurement Units and the development of Smart Grid control concepts, introduce new possibilities for voltage instability prevention. In this work the impact of having a large share of RDG capacity on voltage stability is investigated and a new Hierarchical Agent-Based Voltage Instability Prevention (HABVIP) system for online voltage instability emergency control is proposed. The control philosophy uses the maximum loadability index to determine the amount of active and reactive power load relief necessary to restore stability. The intelligence for this control is provided by agents located in the substations: the substation agents. The load relief is obtained by: increase of local generation, virtual load shedding via adjusting the load tap changers set point, intelligent load control and increasing the reactive power output of Static Var Compensators. The control of the actuators is provided by agents located in the actuators: the actor agents. Verification of the system is done by off-line simulations and by building a real-time hardware in the loop demonstration model.

Integration of long EHV XLPE underground cables in traditionally OHL-based transmission systems can result in abnormal transients caused by large cable shunt capacitance. Transients associated with switching of long cables may result in severe temporary or transient overvoltages. This paper investigates energization transients related to the installation of long 380 kV cables in transmission systems. Voltages and currents at multiple locations were analyzed in the time-domain after energization of different cable lengths in a 80 km mixed OHL-cable connection in the future Dutch 380 kV grid. Moreover, zero-missing phenomenon, as one of the likely events during energization transients of shunt compensated cables, and its countermeasures are discussed. The study comprises time-domain simulations in PSCAD/EMTDC environment, where an accurate distributed frequency-dependent parameter model of the complete Dutch 380 kV grid is developed.

In this paper, we propose a black box model for low-voltage arcs. This model is based on the classical theory with the addition of a corrective term to better fit the small current phase, which is seen to be crucial in determining arc extinction. The model is physically consistent, accounting for nonequilibrium effects in a cold plasma. A mathematical algorithm is proposed for model parameter identification, solving a constrained optimization problem by suitably coupling gradient moves with heuristic search methods. Black box modeling is applied to industrial circuit breakers and very good agreement between model predictions and experiments is observed.

In this paper we investigate how the detailed modelling of uncertainty impacts the assessment of the power system security. We propose a formulation for the inclusion of uncertainty in power system operational security assessment. The model proposed consists of a Monte-Carlo (MC) framework which allows to capture the complex stochasticity of the system inputs using the copula theory for the sampling of the system infeeds, in combination with AC power flow computations for a detailed assessment of the system operation. Taking into account the infeed forecast uncertainty (loads and renewable generation), and the set of possible contingencies, the MC formulation allows the detailed evaluation of the network operation by computing the system risk in terms of Lost Load. Moreover, the model computes the probability of cascading events, pointing out which remedial actions are to be expected and the associated amount of Lost Load. The proposed model is applied to the IEEE 118 bus test system. To highlight how uncertainty modelling impacts the results, we investigate how correlated infeeds affect the severity of estimated system stress. Results show that applying simplifications such as assumptions of independence or approaches that rely on DC approximations could lead to an underestimation of the system risk.

As the concept of capacity market is currently under heavy discussion within the European context, only a few European countries have reached the implementation phase of the capacity market. Significant research efforts have been made to identify the origin, design challenges as well as the underlying framework of capacity markets. This paper evaluates the capacity market in the European context, proposes a method for quantifying the analysis, and provide a set of capacity market framework recommendations to the stakeholders, such as policy makers and market participants among others. This paper proposes four balancing variants within the EU context (EU 27 + Norway, Switzerland), a) Each country performs its own energy balancing, b) Seven balancing zones, c) Three balancing zones and d) Single balancing zone. All four variants are subject to the five generation/demand scenarios that have been developed within the IRENE-40 project, namely Conventional Power scenario - Business as usual (BAU), Carbon Capture and Storage scenario (CCS), Desertec scenario (DES), Renewable scenario (RES) and High Efficiency scenario (EFF). Following market simulations, policy recommendations are laid out for the future direction of the European capacity market design.

The deployment of EVs leads to a shift of the demand from transport to the power sector. This paper shows that in order to perform a realistic evaluation of the EVs integration impacts on a power system, the future developments in the increase of interconnection capacities should be taken into account. For this, three different charging scenarios are developed and tested using a North-Western Europe system model, together with a unit commitment and economic dispatch tool. EVs load time series are generated for each scenario by a stochastic model which is based on real commuting patterns of the Dutch population. The results indicate that EVs load is mainly supplied by conventional generation: gas, coal and nuclear. It is also noted that EVs lead to a very low increase in wind power utilization and even to a substitution of hydro generation.

This paper proposes a multi-TSO collaborative network expansion methodology of for the congestion alleviation by placing new transmission lines to different control areas in the system separately, meanwhile maintaining the security standard of the grid as a whole. Optimal power flow, using Lagrangian multipliers and locational marginal price as optimisation variables is applied. The method provides the optimal location, type, and the number of extra necessary transmission lines for the optimal network structure under the generation and load scenario that the network may encounter in the future. A test case with the New England 39 bus model is presented in this paper for the validity and effectiveness of the proposed method.

In the power system of the future, reliability will play an important role. This reliability is influenced by different developments like the increase in electricity consumption and the use of renewable and distributed generation. It is important to have a good insight into the reliability performance of the system. With probabilistic methods, the reliability of the power system can be analyzed and decisions can be made to maintain the high reliability level that we demand. This paper gives an overview of the different developments in power systems and describes how these developments influence the reliability of the future power system. The possibilities to implement these developments into the probabilistic reliability analysis in network planning and operational planning are discussed. By use of an example, the possibilities and challenges of probabilistic methods in operational planning are illustrated.

Distributed generation (DG) plays an increasing role in the power system. Due to their local character they could in principle be used in emergency situations to prevent a blackout. Classically, however, DGs are uncontrollable. In this paper methods are proposed to use DG as actuator in the Hierarchical Agent-Based Voltage Instability Prevention (HABVIP) system. The control strategy in this system is to obtain a certain amount of load relief in the problem area. Three types of DG are considered: micro-CHPs, greenhouse CHPs and Wind Turbines (WT). For the micro-CHP and greenhouse CHP the output power can be controlled within limits. These limits are determined by the maximum temperature settings. For the micro-CHP a Virtual Power Plant (VPP) scheme is proposed to obtain continuous power output of a group of micro-CHPs that work under thermostatic control. For the WT the output power cannot be controlled. For that reason a method is proposed to use the predicted power generation of this turbine to anticipate for an increase or decrease. The proposed methods are verified by simulations which show that the methods work properly.

This paper presents a Monte Carlo simulation approach for the modeling of the power demand of electric vehicles under the scenario of uncontrolled domestic charging. A detailed transportation dataset for the Netherlands is used to derive the stochastic characteristics of the behavior of vehicles. The stochastic variables are the start/end-time of each trip and the respective travelled distance while the battery state of charge at the beginning of charging is derived by the consideration of the distance traveled since the last charging and the charging history. The stochastic variables are modeled using normal copula function based on the respective correlations and marginal distributions. The total load due to electric vehicles is computed based on the combination of the simulated commuting pattern with the charging profile of a typical electric vehicle battery. The results show that the EV power demand reaches the highest value during the evening peak hours for the residential load, however the peak is significantly lower than maximum which is mainly caused by the low charging time due to a generally low mean traveled distance.

In this paper a strategy is introduced for emergency control of Load Tap Changers (LTCs) to prevent the system from voltage collapse. The method is based on the fact that the power consumed by constant current and constant impedance loads can be lowered by decreasing the secondary voltage of the LTC. This idea is used to develop a method of indirect load shedding. This method calculates, based on a model of the connected load, the voltage set-point of the secondary side of the LTC for a given amount of load that needs to be shed. With simulations it is demonstrated that a LTC can be applied for load relief using the proposed method. A sensitivity analysis is done to study the effect of an error in the load model parameters. Furthermore it is proven that the method can be used to prevent the power system from a typical voltage instability. Finally a proposal for the implementation in a smart grid multi-agent system is presented.

Many decentralized generation technologies are mature today. For the Dutch power system it is expected that in 2020 Decentralized Generators (DGs) form a major (about 35 %) part of the total production capacity. This expectation is true all over the world. A large share of DG will influence the voltage stability of the system. The objective of this paper is to give a clear overview of the consequences of DGs for typical voltage stability problems encountered at transmission level. No particular DG will be studied, but an overview will be given what happens if a DG is based on a certain generator type. Based on theoretical expectations the simulations done in this study show for a typical transmission system that adding DG is generally beneficial for the voltage stability. Mainly three factors are important for the consequence DG has on voltage stability: active power support, reactive power consumption, and voltage support. Taking these benefits into account requires intelligent control of the DGs.

This paper presents the advantages of using wind speed time series models from ARMA-GARCH class. The models are found using good statistical practice and are able to capture the most important characteristics of the data like distribution, time dependence structure and periodicity in a satisfying manner. It is shown that the models offer several crucial advantages. The artificial wind speeds simulated from the obtained models are statistically indistinguishable from the wind speed time series measurements recorded in other years than the original data. Moreover, models can contribute to the considerations of extreme scenarios of wind power generation by simulating wind speeds characterized by a very high energy content. Thanks to the use of continuous cdf transformations, the synthetic time series do not possess the measurement error.

The Newton-Raphson method is widely used to solve load flow problems. Traditionally a direct solver is used to solve the linear systems within this method. In this paper we explore the use of an iterative method to solve the linear systems, leading to an inexact Newton-Krylov method. The main parameters of this method are the preconditioner and the forcing terms. Several candidate choices for these parameters are discussed and tested. With the proper preconditioner, and forcing terms, the inexact Newton-Krylov method is shown to greatly improve on using a direct solver.

In the Dutch power system the power consumption is increasing while the transmission and distribution system capacity is not increasing at the same rate. Furthermore due to the increasing amount of decentralized generation, by for example micro-CHP units and wind turbines, the power flows in the power system are changing. In weak sub-transmission and distribution grids an increase in the number of voltage stability problems is expected. However: with the large share of decentralized generation we have the solution for voltage problems already there. In this paper we propose a new Hierarchical Agent Based Instability Protection System. In this paper the idea is described and a theoretical justification is given, in a later stage of the project we will verify the system with the Real-time Digital Simulator and external controls.

The fast growing application of sustainable energy sources imposes major structural changes on the current electric power systems. One of these structural changes is to make use of large variable speed wind turbines within the conventional electrical power networks. The installation of these wind turbines has, indeed, indispensable impacts on the dynamic behavior of the existing electric power systems. Thus, it is important to gain a rather generalized overview on how these wind turbines, which mostly use Doubly Fed Induction Generators (DFIGs), affect the system stability. This paper performs an analytical analysis for the indication of small disturbance rotor angle stability in the power systems equipped with variable speed wind turbines using DFIGs. Also, in order to consider the stochastic characteristic of the sustainable energy sources, the paper applies an iterative-stochastic method to analyze the small disturbance angle stability. The suggested iterative-stochastic methodology is numerically verified, within this paper, by getting applied to an electric power test system.

State estimation is an important tool for system operators. The state of the power system is defined by the voltage magnitudes and phase angles at all buses. The state estimator (SE) determines this state based on a set of redundant measurements.

High resolution measurements on the post-arc current in vacuum circuit breakers reveal a period, immediately following current-zero, in which the voltage remains practically zero. The most widely used model for simulating the interaction between the post-arc current with the electrical circuit lacks a proper explanation for this event, and hence it needs to be complemented. We demonstrate that the breaker's electrical behaviour during this zero-voltage period can be explained by using the theory of a Langmuir probe. Such probes are used to investigate plasma properties, such as the ion density and the electron temperature, and we extrapolate its theory to the vacuum circuit breaker. The simulation results obtained with this model are in good agreement with measured data.