This review paper, prepared for this second special issue on lightning of the IEEE Transactions on Electromagnetic Compatibility, summarizes major publications on lightning and lightning protection since the first special issue published in November 1998, i.e., during the last decade. The review is organized in the following five sections: lightning discharge-observations, lightning discharge-modeling, lightning occurrence characteristics/lightning locating systems, lightning electromagnetic pulse and lightning-induced effects, and protection against lightning-induced effects.

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Overview of Recent Progress in Lightning Research and Lightning Protection

One of the weakest components of modern transient simulation software is the transformer model. Many opportunities exist to improve the simulation of its complicated behaviors, which include magnetic saturation of the core, frequency-dependency, capacitive coupling, and topologically correctness of core and coil structure. This paper presents a review of transformer models for simulation of low- and mid-frequency transients. Salient points of key references are presented and discussed in order to give an accessible overview of development, implementation and limitations of the most useful models proposed to date. Techniques for representation of the most important behaviors are examined, with the intent of providing the needed foundation for continued development and improvement of transformer models.

Transformer modeling for low- and mid-frequency transients - a review

With the fast-paced changing technologies in the power industry, new references addressing new technologies are coming to the market. Based on this fact, there is an urgent need to keep track of international experiences and activities taking place in the field of modern transformer design. The complexity of transformer design demands reliable and rigorous solution methods. A survey of current research reveals the continued interest in application of advanced techniques for transformer design optimization. This paper conducts a literature survey and reveals general backgrounds of research and developments in the field of transformer design and optimization for the past 35 years, based on more than 420 published articles, 50 transformer books, and 65 standards.

Transformer Design and Optimization: A Literature Survey

This paper proposes a load survey system to determine the load characteristics of various customer classes in an electric utility company. The questionnaires are adopted to find the power consumption of key electric appliances. The actual power consumption of hundreds of customers are collected by intelligent meters. Sampling theory has been applied to find the proper sample size of both questionnaires and field tests so that the customer load characteristics will be derived with sufficient confidence level. Statistical analysis is then performed to find the power consumption model of each customer class based on the power measurement of field tests. The temperature effect on the power consumption of each customer class is also investigated by differentiating the proposed power consumption model with respect to the ambient temperature. The proposed method has been adopted by the Taipower company to better understand the customer load characteristics to support various functions of power system planning and operation in a more effective manner.

Determination of customer load characteristics by load survey system at Taipower

Black start, the restoration of a power system after a complete blackout, is a key issue to the safety of power systems. The reasonable network reconfiguration is necessary for establishing the main network and restoring loads quickly. Based on topological characteristics of scale-free networks and discrete particle swarm optimization, a skeleton-network reconfiguration strategy is proposed in this paper. Through calculating node importance degrees, priorities of sources and loads could be scaled quantitatively. Then, network reconfiguration efficiency, an index represented by network structure and subjected to restoration constrains, is used to evaluate the reconfiguration effect. Furthermore, discrete particle swarm optimization is employed in reconstructing skeleton networks that relieve reconfiguration burden considerably. Application examples verify that several optimal reconfiguration schemes achieved from the strategy can provide dispatchers an effective decision support under the uncertain system situation.

Skeleton-Network Reconfiguration Based on Topological Characteristics of Scale-Free Networks and Discrete Particle Swarm Optimization

Soil ionization occurs around a grounding electrode when current density in the soil exceeds a critical value and reduces grounding resistance. This paper proposes a current-dependent grounding resistance model considering the soil ionization. The proposed model is derived on the basis of energy balance of the soil ionization. The resistivity of the ionization zone depends on energy stored in the zone. Analytical expressions of the model are proposed to estimate the zone resistivity. The model is verified by comparing it with experimental results.

Current-dependent grounding resistance model based on energy balance of soil ionization

In this paper a new transformer model, named ‘geometrical’, is developed, based on the circuit analysis of its magnetic core. The method is general and can be used for any type of multiphase multiwinding transformer. The model simulates the transformer as a set of coupled branches and can be incorporated into the widely known electromagnetic transients program (EMTP). A basic advantage of the model is that it can represent any asymmetry of the transformer magnetic circuit. As a study case, the model of an actual 280 MVA autotransformer is derived and used for the simulation of various steady state and transient conditions.

Generalised transformer model based on the analysis of its magnetic core circuit

In this paper the energization of a transmission line, a phenomenon particularly related to black start studies, is simulated using the Electromagnetic Transient Program (EMTP). The effect of several parameters, such as the line models used in EMTP, the line transposition, the existence of a surge arrester and the transient behaviour of the synchronous generator are investigated. >

Simulation of long transmission lines energization for black start studies

In this paper the overvoltages produced by switching the primary side of reactor loaded transformers are simulated using the Electromagnetic Transients Program (EMTP). Attention is focused on transformer modelling. Five general three-phase transformer models are used and from the results obtained, and comparisons with field tests, positive conclusions concerning the reliability and the accuracy of these models in the study of switching fast electromagnetic transients are drawn. >

Three phase transformer modelling for fast electromagnetic transient studies

An efficient algorithm for the implementation of hysteresis effect in three phase transformer models for electromagnetic transient studies is presented. It is based on a simplification of the well-known Preisach model requiring few data, easily available, while it provides results close to the experimental ones. The model is validated by comparing measured and calculated results obtained from tests on a magnetic material used for the construction of transformer cores and a laboratory three-phase transformer.

J.M. Prousalidis

Papers

Current-dependent grounding resistance model based on energy balance of soil ionization

Generalised transformer model based on the analysis of its magnetic core circuit

Simulation of long transmission lines energization for black start studies

Three phase transformer modelling for fast electromagnetic transient studies

Representation of hysteresis in three-phase transformer models for electromagnetic transients