Akiyoshi Tatematsu

Central Research Institute of Electric Power Industry | CRIEPI · Electric Power Engineering Research Laboratory

Nowadays, plenty of sensitive electronic devices are installed in secondary circuits in substations. When lightning strikes a substation and transmission line, lightning currents flow into the grounding structure of the substation through shield wires and lightning surge arresters in the primary circuit, and lightning overvoltages are induced on co...

Surge arresters with a series gap are commonly installed in distribution lines to effectively protect insulators, transformers, and other equipment from lightning threats in Japan. On the other hand, it has been well known that the high-altitude electromagnetic pulse (HEMP) at an early stage, called E1 HEMP, may extensively cause overvoltage on dis...

A high-frequency electromagnetic plane wave arises owing to a high-altitude electromagnetic pulse (HEMP), which may cause overvoltages in distribution lines and insulation failure. To protect distribution lines from such overvoltages properly, it is necessary to evaluate the effectiveness of countermeasures. Nowadays, the finite-difference time-dom...

In general, the causes of lightning faults on medium-voltage distribution lines are classified into indirect and direct lightning. In medium-voltage distribution lines in Japan, the lightning outages associated with indirect lightning are less frequent than those associated with direct lightning, as surge arresters are installed at close intervals...

Methods based on both time ( t )-domain and frequency ( f )-domain have been used for electromagnetic transient (EMT) analysis using both circuit-theory and field-theory approaches. Methods based on circuit theory are fast and convenient but may become inapplicable to many engineering problems due to simplifications such as the transverse electro...

Currently, plenty of sensitive electronic devices are installed in secondary circuits in substations and power plants. Electronic devices may malfunction and become damaged owing to electromagnetic disturbances caused mainly by lightning surges. To protect electronic devices properly, it is useful to predict electromagnetic transient phenomena and...

Lightning currents may cause damage to power equipment in a substation and a transmission line (TL), and thus, to protect power equipment properly, it is required to install effective lightning protection measures on the basis of the prediction of electromagnetic transient phenomena through numerical simulations. In this article, using an electroma...

The installation of effective lightning protection is necessary to protect power equipment and sensitive electronic devices and guarantee human safety in nuclear power plants. To evaluate the effectiveness of countermeasures against lightning, it is necessary to predict lightning surge phenomena. Recently, the finite-difference time-domain (FDTD) m...

A direct lightning strike to a transmission line tower may cause overvoltages and insulation failures, and to avoid unexpected insulation failures and protect power equipment, it is necessary to install effective lightning protection measures. To design effective countermeasures, the prediction of lightning surge phenomena is required. The finite-d...

The finite‐difference time‐domain method is one of the most widely used numerical electromagnetic computation techniques, and it has become an effective tool for analyzing electromagnetic transient phenomena in three‐dimensional structures and grounding systems. However, the available approaches for representing thin wires apply only to bare conduc...

Switching overvoltages on busbars occur during the operation of circuit breakers and disconnectors, in power plants and substations. The transient electromagnetic interferences arising from the switching surges may cause disturbances in sensitive electronic devices in low-voltage control circuits and may induce voltages on other busbars grounded fo...

To protect power equipment and electronic devices in low-voltage control circuits in power plants and substations from abnormal voltages such as lightning or switching surges, it is necessary to design effective protection measures based on the prediction of surge phenomena. Nowadays, full-wave numerical approaches have become effective tools for a...

Disturbances in low-voltage control circuits in substations and power plants occur due to lightning or switching surges. Adequate protection of electronic devices in low-voltage control circuits requires the capacity to predict surge phenomena and to evaluate the effectiveness of protection methodologies. In this paper, we present and validate a te...

In this paper, we present a stable method for simulating passive distributed networks connected to linear and nonlinear devices using the time marching (TM) method. The method is based on the use of the Z-transform for analyzing and obtaining the TM equations, and the application of cepstrum for preventing the apparition of unstable poles in the Z-...

In electric power systems, microwave relay stations are employed to exchange information using electromagnetic radio waves to control the systems. Some microwave relay stations are built on tops of mountains, which causes a high incidence of lightning strikes to microwave towers, and the lightning strikes may result in disturbances of microwave rad...

We discuss the stability of the time marching method when applied to problems involving lossy transmission lines with nonlinear loads. One of the causes of TM instability is the apparition of unstable poles in the TM deconvolution equations. We present a novel approach based on the application of cepstrum to ensure the stability of the TM solutions...

The operating voltages of low-voltage control circuits in power plants and substations have decreased with the installation of digital control equipment. This increases the susceptibility of control equipment to abnormal surges, which arise mainly from lightning. To protect control equipment from lightning, it is necessary to predict lightning surg...

The prediction of surge phenomena is required for designing effective lightning protection methodologies, and circuit-theory-based simulation techniques, which assume the transverse electromagnetic (TEM) mode, have traditionally been widely employed for lightning surge analysis. Recently, the finite-difference time-domain (FDTD) method, which is on...

Microwave relay stations are key components in controlling power grids and maintaining their stability, but lightning strikes to the stations may cause faults, malfunctions, or even physical damage to microwave radio equipment. To protect equipment from lightning, it is necessary to predict surge phenomena in a microwave relay station, and design e...

A thin wire model for FDTD simulations is proposed for the study of transient potential rises and currents in a grounding grid. The model is an extension of the formalism of Holland, and it is compared with the thin wire model of Baba, Nagaoka, and Ametani, using a case study previously validated with measurements. Special interest is drawn on the...

The finite-difference time-domain (FDTD) method is a very effective tool for predicting surge phenomena in 3-D structures such as buildings and transmission line towers and in grounding systems such as grounding grids. In this paper, we propose a new technique for representing a coaxial cable for FDTD-based surge simulations. In this technique, the...

Lightning electromagnetic pulse (LEMP) is a severe threat to sensitive electronic devices installed in buildings. To protect these devices from LEMP effects, the evaluation of the electromagnetic fields inside of the building is required. Although numerous studies have been devoted to the analysis of these fields stemming from direct and indirect l...

Lightning electromagnetic pulse (LEMP) is a severe threat to sensitive electronic devices installed in buildings. In order to protect these devices from LEMP effects, the evaluation of the electromagnetic fields inside the building is required. Numerous studies have been devoted to the analysis of these fields stemming from direct and indirect ligh...

A locating system based on an advanced time difference of arrival (TDOA) estimation method is developed to locate the position of a discharge source to avoid pulsed electromagnetic interference (PEMI) with the surrounding radio communication environment. In general, from the waveforms of PEMI waves received by an antenna array, the source position...

Microwave multiple radio relay stations are often built on mountains, and the stations are susceptible to damage from lightning. Therefore, it is important to take adequate lightning protection measures to ensure that communication devices are not damaged by any lightning surge current that penetrates from a lightning rod fitted on such stations. I...

To suppress the lightning-induced voltages on a distribution line, lightning arresters and/or overhead shielding wire can be installed, and the effectiveness of these countermeasures are usually studied by simulations. Traditionally, field-to-transmission line coupling techniques based on the distributed-parameter circuit theory are used for the ca...

The operating voltages of low-voltage control circuits in power stations and substations have become lower with the installation of digital control equipment. This significantly increases the risk of faults and malfunctions of the circuits resulting from overvoltages in the control circuits due to lightning and switching surges. Therefore, the char...

Induced voltages and currents on electrical wirings in a building directly hit by lightning are studied by using numerical electromagnetic analysis. It turns out that installation of SPD is indispensable at low-voltage wirings and communication lines. The effectiveness and energy rating of SPD installed on the electrical wirings are also discussed.

Audible noise arising due to corona discharge on overhead transmission line conductors is one of the important factors in the design of the transmission line conductors. Therefore, the audible-noise characteristics of the conductors are often measured using a corona cage. In the corona cage, an electric field distribution is generated around the c...

Pulsed electromagnetic waves causing interference may be emitted from power equipment owing to a discharge phenomenon, which may occur at a faulty point, such as an unintended narrow gap between metal supports or a deteriorated insulator. Therefore, it is necessary to localize the electromagnetic source or estimate its direction of arrival (DOA) ef...

Induced voltages and currents on electrical wirings in a building directly hit by lightning are studied by using numerical electromagnetic analysis. It turns out that installation of SPD is indispensable at low-voltage wirings and communication lines. The effectiveness and energy rating of SPD installed on the electrical wirings are also discussed.

Recently, the FDTD (Finite Difference Time Domain) method, which directly solves Maxwell's equations, has been applied to lightning surge problems involving electrical wires in three-dimensional arrangements, such as power and telecommunication circuits. Lightning arresters are installed to protect the circuits from abnormal voltages due to lightni...

A pulsed electromagnetic interfering wave may be emitted from power equipment owing to a discharge phenomenon, which may occur at a faulty point, such as an unintended narrow gap between metal supports or a deteriorated insulator. Therefore, it is necessary to localize the electromagnetic interference source or estimate its direction of arrival (DO...

Recently, numerical electromagnetic field computation methods, which solve Maxwell's equations, have become a practical choice for the lightning surge analysis of power systems. Studies of lightning surge response of a transmission tower and lightning-induced voltages on a distribution line have already been carried out using the numerical electrom...

The operating voltages of low-voltage control circuits in power plants and substations have become lower owing to the installation of digital-control equipment. This significantly increases the risk of faults and malfunctions of such circuits due to abnormal voltages in the control circuits induced by lightning and switching surges. Therefore, the...

The FDTD (Finite Difference Time Domain) method, which is used for the computation of electromagnetic fields, is a useful tool for surge problems in three-dimensional arrangements, which cannot be rigorously treated by simulation methods such as EMTP (Electromagnetic Transients Programs) based on circuit theory. In the FDTD method, thin wires such...

This paper presents new features recently added to a general-purpose surge simulation code based on the Finite Difference Time Domain (FDTD) method. The added features include various-shape conductor models, lumped-parameter circuit-element models, a lightning-channel model, and an integrated analysis environment (IAE). For precisely modelling the...

The adaptive cross-approximation (ACA) technique is applied to accelerating an inverse-problem solver that estimates charge distribution on a dielectric spacer. The ACA generates an approximated system-matrix that enables us to carry out high-speed inverse calculation. We designed an approximation procedure based on ACA with some additional concept...

We have been studying a multi-point charge measurement method using an electrostatic probe. In this technique, charge densities x must be estimated from the probe outputs b by an inverse calculation based on an equation Ax = b. The matrix A is obtained by applying a numerical field calculation technique. When the matrix A is in ill-condition, the s...

The adaptive cross-approximation (ACA) technique is applied to accelerating an inverse-problem solver that estimates charge distribution on a dielectric spacer. The ACA generates an approximated system-matrix that enables us to carry out high-speed inverse calculation. We designed an approximation procedure based on ACA with some additional concept...

If a return stroke occurs nearby a distribution line, the electromagnetic field radiated by the return-stroke current induces voltages on the distribution line. A lightning arrester is often applied to the distribution line to suppress such overvoltage. In this study, the finite difference time domain (FDTD) method, in which Maxwell's equations are...

Charge accumulation on thick solid dielectrics may seriously influence surface discharge and insulation characteristics in SF6, oil, or vacuum, which are the leading insulators for the recent high voltage equipment. Nevertheless, charge measurement technique in such environment has not been fully developed in practical level. One of the authors onc...

The measurement of accumulated surface charge for thick specimens requires multipoint probe outputs to establish the inverse calculation for the determination of an unknown charge distribution. Until now, studies on the various errors associated with the measurement have been conducted only for simplified arrangements mainly in axisymmetric geometr...

We have derived analytical expressions of the potential and electric field generated by a triangular surface charge that has a second- or third-order charge density distribution on each element. These expressions are applicable to the surface charge method (SCM) for calculating electric field in three-dimensional arrangements. In general, the highe...

We have derived analytic expressions of the potential and electric field generated by a triangular surface charge that has a second-order or third-order charge density distribution on each element. These, expressions are applicable to the surface charge method (SCM) for electric field calculations in three-dimensional arrangements. In general, the...

This paper proposes analytic expressions of the potential and electric field generated by a triangular surface charge which uses a second-order function for representing the charge density on the element. These expressions are applicable to the surface charge method in electric field calculations. In general the high-order charge density improve th...