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This paper reports an experimental and numerical Investigation into the surge current distribution in a reinforced concrete structure during a lightning stroke. An analytical method, which is based on a circuit approach, is described. The steel structure is modeled by a series of coupled φ-type circuits. The capacitance in the circuits is calculated by the means of average potential method, while the Inductance is evaluated by the Neumann’s formula. The effect of the earth (ground) is taken into consideration by the method of images. The analytical method was demonstrated and validated on three models of steel structures, and can be applied to estimate current distribution in the lightning protection system of a building.

The transient near-field of the electrostatic discharge (ESD) is strongly affected by the discharge current waveform. After analyzing several typical mathematical descriptions of the ESD current for the contact mode, two new mathematical descriptions of ESD current were constructed according to the polynomial of pulse function. These descriptions have the continuity of the first derivative at t=0 and are time-integrable. They proved to have little relative error compared to the IEC61000-4-2 standard

The lightning overvoltage is one of key issues to design the insulations of transmission line and power apparatus. Usually, the influence of the impulse corona on lightning overvoltage is ignored. Fully understanding the corona characteristics of 1000 kV UHV transmission line is helpful to understand the actual wave process and realize a suitable insulation design of 1000 kV UHV system. Experiments on the lightning impulse corona characteristic of bundle conductors for 1000 kV transmission lines are carried out in China UHV AC Test Base and the impulse corona Q-V curves of different bundle conductors are obtained. The results show that impulse corona causes the capacitance of the conductor increasing. Analysis on the Q-V curves shows that the positive impulse corona occurs a little time later than the lightning impulse voltage exceeds the corona inception voltage and the delay time is tenth of microsecond.

Detailed positive corona discharge characteristics, such as the corona onset voltage, pulse amplitude, repetition frequency, average corona current, rise time, and half-wave time, are systematically studied under different air humidity with a single artificial defect electrode. The experimental results indicate that the pulse amplitude decreases with the increase of air humidity; meanwhile, the repetition frequency increases as the air humidity increases. This phenomenon is different from that of negative corona discharge. Therefore, to have an insight into the mechanism of humidity influence on positive corona discharge, a positive corona discharge model based on the continuity equations is utilized. The simulations present a dynamic development of positive corona discharge and, meanwhile, reveal the humidity influence on positive corona discharge.

[1] Time-varying diapycnal diffusivity signals are estimated using the fine-scale parameterization method from high-resolution CTD data along three repeat sections in the northwestern Pacific Ocean. Indicative of the parametric subharmonic instability (PSI), locally-elevated diapycnal mixing is detected alongallthree sections within the 25°–29°N band where bottom topography is relatively featureless. Due to their proximity to the semidiurnal internal tide generation sites, the two sections along ∼137°E have a time-mean diffusivity value 2.5 × 10−5 m2 s−1 in the 300–2,000 m upper ocean. In contrast, it is 1.2 × 10−5 m2 s−1along the 165°E section. The time-varying diffusivity along both sections is dominated by signals whose vertical structure resembles the local first dynamic normal mode profile. At the 137°E site of 25°–29°N, the local spring-neap modulated semidiurnal tidal current is found to lead the CTD-derived diffusivity time series by 6 days and can alter the diffusivity level by 0.24 × 10−5 m2 s−1. Similarly, the concurrent surface wind work is found to modify the diffusivity level by 0.35 × 10−5 m2 s−1. The combined spring-neap tide and wind work forcing explains 47% of the observed, time-varying diffusivity signals.

[1] Enhanced mesoscale eddy activity northeast of the Hawaiian archipelago was investigated by using the high-pass filtered satellite altimetric sea surface height (SSH) data of the past 16 years. The level of eddy kinetic energy (EKE) shows significant interannual variations, which appear well correlated to the large-scale atmospheric wind forcing associated with the Pacific Decadal Oscillation index; the EKE levels in the area along the Subtropical Front zone in 1997–1998 and 2003–2005, for example, were three times as large as those in the low EKE years. Spectral analyses in the 3° latitude by 5° longitude subregions revealed the dominant mesoscale periods ranging from 90 days near 18°N to 180 days near 36°N. A 3-layer quasi-geostrophic model constrained by World Ocean Atlas 2005 climatologies was used to explore instability of the regional circulation. The analysis shows a geographical match between baroclinic instability strength and the observed RMS SSH variability and a temporal match between seasonally varying instability strength and the observed seasonal EKE modulation, and suggests that baroclinic instability by the vertically sheared, regional mean circulation provides the energy source for the enhanced eddy variability northeast of the Hawaiian archipelago.

If the microgrid is stroke by lightning, the lightning overvoltage which transferred though distribution transformer has great influence on the safety of the microgrid. The models of microgrid and high-frequency transformers are established based on the electromagnetic transient calculation program PSCAD/EMTDC. The transferred overvoltage with different lightning strike position in microgrid is researched in this paper. The effect of surge arresters on restricting overvoltage is also analyzed. The simulation results show that surge arresters must be installed at both sides of transformer due to the high overvoltage when the transformer has no load. If the transformer is connected with cables, the overvoltage will be reduced. The longer the cable is, the lower the overvoltage is. The types of loads have a little influence on the overvoltage.

Now microgrid has aroused increasing attention due to energy sustainable development and the development of distributed generations (DG), such as micro-turbines, gas turbines, wind power, photovoltaic and fuel cells. This paper introduces the basic structure of microgrid and summarizes the overvoltages that can occur in microgrid, including ground fault overvoltages, resonant overvoltages, overvoltage related to voltage regulation, switching overvoltages of inner microgrid, transfer overvoltages from distribution network (such as lightning and switching overvoltages). By analysis, this paper obtains the following conclusion: resonant overvoltages and lightning stroke transfer overvoltages are the most serious for microgrid.

Lightning caused surge voltages in low-voltage AC power circuits are studied statistically based on the Monte Carlo method in this paper. The finite difference time domain (FDTD) method is used to solve the multi-conductor transmission line equations. A transformer model is incorporated into the FDTD solution. Both direct and indirect lightning strikes are taken into account in the statistical evaluation. Results show that installing surge arresters on 10 kV overhead lines has a notable influence on the surge level on 220V sides.

Covered conductors and compact configuration with triangle spacers for 10-kV distribution lines have brought many advantages and benefits in China. In the past, the polymeric spacers cast with polycarbonate material had been designed and applied to make the distribution line compact. The reason that breakage faults occurred on compact distribution lines with polymeric spacer is because the polymeric spacers have bad pollution flashover performance, and the polycarbonate material used is not suitable for outdoor insulation. The pollution experiment of the covered distribution line supported by triangle spacers shows the flaw in the insulation layer is the key reason to generate flashover in a humid environment, which would be formed in the insulation layer of the covered conductor under sun radiation or under lightning effect. A new kind of triangle composite spacer, which is suitable for heavy pollution area, is designed to prevent breakage faults of covered conductors caused by leakage current. From the experimental results, the corona initial voltage and the flashover voltage of 10-kV covered distribution line fixed with composite spacers increased an average of 41.9% and 60.3%, respectively, comparing with the tested data of covered conductor fixed with polymeric spacers. The developed composite spacers can highly improve the pollution performance of 10-kV covered distribution lines. The field applications show the composite spacers are effective, and can prevent conductor breakage faults caused by leakage current.

Adoptingcoveredconductorsandcompactconfigurationhasbecomethetendencyinthereno-vationofdistributionnetworkinChina. Advantagesofcompactconfigurationarediscussedinthispaper, which can further save the passage of distribution line, and can easily realize multiple linesin a pole. The movement process of phase conductors is analyzed by the Chord Forced Equationof the mechanical theory to obtain the relationship between the phase spacing of triangle spacerand the span between two neighboring spacers. The suitable phase spacing and spacer span arepresented for polymeric and composite spacers. The superiority of compact configuration againstlightning protection comparing with traditional distribution lines was analyzed.KEYWORDS:coveredconductor,compactdistributionline,trianglespacer,lightningprotection,induced voltage, movement process

The corona effect of HVDC transmission lines affects the electromagnetic environment significantly. A numerical method to calculate the ion flow field caused by corona effect in the vicinity of multi-circuit HVDC transmission lines is described. Deutsch assumption, a commonly used simplification in traditional numerical methods is eliminated. Skills of initial value estimation and boundary process are introduced to improve the stability and efficiency of calculation. Bundle conductors and ground wires are taken into account in this simulation model. The ion flow field of a ± 500kV HVDC project with bipolar lines on the same tower is simulated. The electrical field and ion current density on ground level are compared among different line arrangements.

A numerical method to calculate the ion flow field in the vicinity of multi-circuit DC transmission lines is described. Details of the transmission lines such as bundle conductors and ground wires are taken into account in this simulation model. Deutsch assumption, a commonly used simplification in traditional numerical methods is eliminated. The ion flow field of a ±500 kV HVDC project with bipolar lines on the same tower is simulated. The electrical field and ion current density on ground level are compared among different line arrangements.

In this paper, an upwind finite element (FE) based algorithm devoted for the computation on the ion flow field of bipolar high voltage direct current (HVDC) transmission lines. The choice of initial charge density value on conductor surface is discussed to satisfy the requirement of bundle conductor computation. Non-reflective boundary condition is introduced to improve the computational efficiency. Comparison between measured and computed ground level electric field and ion current density shows satisfactory agreement.

DC biasing current through the neutral point of ac power transformer would lead the power transformer to generate more vibration and sound, this will do harm on power transformerspsila core pieces or windings and finally will threaten the safe operation of the transformers. This paper described the principle of DC biasing, designed a new DC biasing experiment to analyze how the experimental transformerpsilas vibration and sound change along with the value of DC biasing current or windings voltage and finally some curves were given in order to show the direct connection between vibration peak value, sound pressure and DC current.

The electromagnetic transients of lightning protection system (LPS) under direct lightning strike is studied using NEC2. By employing antenna return-stroke model, lightning channelpsilas inducing effect and finite conductivity of ground are all taken into account. Results show that the lightning channelpsilas inducing effect tends to decrease the current flowing through horizontal conductors, and increases the current flowing through vertical conductors near the striking point. The results obtained under perfect ground assumption have a good agreement with the published experimental results. The simulation also predicts that the finite conductivity of the ground affects the branch current significantly, it increase the LPSpsilas current dissipating efficiency, the higher the soil resistivity, the more uniform the current flowing in vertical conductors.

The line surge arrester with series gap can effectively improve the lightning protection performance of the transmission line, and guarantee its safe operation. This paper discussed the design of two different series gap structures, and their influence on the line surge arresters. The so-called "transverse discharge" between the grading ring of the insulator to the upper discharging electrode of the series gap is discussed. At last, the paper introduced the application and effects of line surge arresters in China. Line surge arresters have achieved good application effect, which have become the main lightning protection measures of transmission lines.

The wide-band frequency EM noise is generated during the processes of firing and turn-off of thyristor valves in converter stations. It will be conducted along the primary circuitry into HV devices located in the DC yard, and the radiated EM noise is generated because of the antenna effect. The noise may interfere with the systems in or around the DC yard by the way of radiated coupling. The DC buses are the most important interference source in the DC yard. A method of simulation analysis based on the Method of Moments is proposed. The EMI level of the ± 500-kV converter stations of the Guizhou-Guangdong ±500-kV HVDC transmission project in China, are analysed in the paper.

The wide-band frequency EM noise is generated during the processes of firing and turn-off of thyristor valves in converter stations. It will be conducted along the primary circuitry, and may interfere with secondary systems by the way of conducted and radiated coupling. The plusmn800-kV UHVDC transmission project is one of newly developed technique and used barely in the world. The EMI problem is one of most important issue that should be studied deeply in the stage of designing. A method of conducted EMI analysis based on time- domain wide-band circuit simulation, as well as a method of radiated EMI analysis based on the Method of Moments, are proposed and verified in the paper. The EMI level of a plusmn800-kV converter station, which is planned and being designed in China right now, are presented.

The electro-optical modulator based on Pockels effect implements the transition from electrical signal to optical signal. This makes using optical fiber in EMC measurements come true. This paper describes the principle of modulators based on Pockels effect, designs the modulator with high precision, calculates the electric field in the modulator, discusses the parameters of the modulator, and gives the equivalent electrical circuit.

[1] During May to November 2004, 20 profiling floats were deployed in the recirculation gyre (RG) region south of the Kuroshio Extension (KE). With the KE and RG being in a stable state, most of these floats remained within the RG, resulting in a large number of satellite position fixes for estimating the velocities at the parking depth (1500 db) and a large number of temperature/salinity profiles for estimating the geostrophic velocities above the parking depth. The flows of the RG at different depths in the upper 1500 db are found to be approximately parallel to each other, with the speed at the surface (35 cm s−1) being about three and a half times larger than that at the parking depth (10 cm s−1). By analyzing the full-depth conductivity-temperature-depth profiles in the RG, in addition to the velocity estimates, we found that the vertical structure of the RG velocity field was dominated by the barotropic and first baroclinic modes. The two modes are combined in such a way that the resulting RG circulates anticyclonically in the same direction from the surface to the bottom and has an anticyclonic bottom velocity on the order of 5 cm s−1. From the barotropic component (depth-averaged) of the RG velocity field, the RG transport with one standard error is estimated at 101 ± 8 × 106 m3 s−1.

This paper studies the overvoltages on the low voltage power supply system caused by lightning surge. We use a 1/5 scale iron model to simulate a building's structure, a surge generator which can generate 1.2/50-8/20 mus waveform used as lightning surge, an SPD which constrain lightning surge under 1 kV, and some polyvinyl chloride cable. In this experiment, different load elements such as resistors, capacitors and inductors are applied, different lengths of cable, such as 1 m, 4 m, different ways of laying the cable and positions where surge is applied are studied. The results show the rule that capacitive load gender the highest overvoltage in all kinds of loads, and the overvoltage is higher when the capacitance increasing. It is also found that the longer the cable is, higher the overvoltage is, however this is opposite when the load is capacitive. Furthermore, the results of our digital simulation by PSCAD/EMTDC (electro-magnetic transients including DC) are compared with the experimental results, and they are well matched.

Reverberation chambers are used widely for EMC testing in industry. The design of the mechanical stirrer should be considered artistically. This paper introduces a split stirrer design, the simulation result shows the good performance of this stirrer and a prototype chamber is built according to the simulation. The critical parameters of the reverberation chamber are analyzed in detail. Four calibrations are processed to evaluate the testing repeatability and validate the performance of the split stirrer.

The calibration of the reverberation chamber is very important. The influence of the position of the transmit antenna on the performance of the reverberation chamber is analyzed according to the measurement data. The parameters such as field uniformity, quality factor and the receiver antenna calibration factor are analyzed in detail on the different positions of the transmit antenna. It reveals that the position of the transmit antenna has insignificant influence on the testing repeatability and the orientation of the transmit antenna aligning to the stirrer is a better way for calibration and testing.

The AC voltage measuring system is one of the most importance paths for electromagnetic interference propagation in HVDC converter station. In this paper, a wide-band simulation model is proposed to analyze the electromagnetic interference propagation in it. Experimental study is also carried out to obtain the EMI noise level in measuring system. Comparing with experimental results, the calculation results and simulation model are verified.

The power line carrier (PLC) system used in HVDC converter station is connected directly to the primary system via coupling devices, and may be interfered by the electromagnetic noise produced by valves or switch operation procedure. In this paper, the EM noise in PLC system of plusmn500-kV HVDC converter station is measured in the steady state. The transient disturbance during the switch operation procedure appearing in PLC system is also taken into account in this paper. The characteristics of EMI in PLC system are analyzed based on the experimental results

The alternating-direction-implicit finite-difference time-domain method (ADI-FDTD) is considered as a very efficient algorithm. The key problem of the implementation of the ADI-FDTD method is to solve the tridiagonal matrix system. Two numerical algorithms for the tridiagonal matrix system are analyzed in detail in this paper. The interpretations for the stability of the algorithms are also given clearly

A numerical method to analyze the potential distribution along long ceramic insulator strings on the head of transmission tower is presented. The method uses charge simulation method and boundary element method to obtain the capacitances among insulators, transmission lines, and tower, and then uses circuit theory to analyze the potential exerted on each insulator. The potential distribution along insulator strings on the head of 750 kV transmission tower is analyzed

[1] A decade-long satellite altimeter data set is used to analyze the annual variations in the sea surface height (SSH) field northeast of the Hawaiian Islands. The annual harmonic amplitudes for the SSH and the along-island geostrophic flow are 2–4 cm and 2–4 cm s−1, respectively. Although these values are an order of magnitude smaller than the regional mesoscale eddy signals, the annual SSH signals have a robust spatial structure that can be expressed as a function of distance northeastward away from the Hawaiian Islands. The annual SSH signals are then described by using trapped annual waves and a basin-scale non-propagating signal. Using the linearized vorticity equation, we suggest that the trapped annual waves are baroclinic Rossby waves that decay from the Hawaiian Islands.

The transient near-field of the electrostatic discharge (ESD) is a kind of high power transient phenomenon, which strongly affects the operation of the electronic devices. In this paper, the transient field of the indirect electrostatic discharge through the vertical coupling plane (VCP) is numerically simulated by using the FDTD method with the PML. The configuration of the current source is considered carefully. The simulation results on different positions show different transient effects. The simulated data are compared with those measured by an optic testing system.

[1] The currents in the Aleutian Basin of the Bering Sea and in the subarctic North Pacific near the dateline in summer 1993 are described, based on Shipboard Acoustic Doppler Current Profiler and Lowered Acoustic Doppler Current Profiler velocity measurements and on conductivity-temperature-depth profiles. The strongest flow is the Alaskan Stream with velocities up to 90 cm s−1 and with a subsurface core as narrow as 30 km at about 150 m depth. Velocity at the bottom below the Alaskan Stream could not be distinguished from zero. The inflow of the Alaskan Stream through Amchitka Pass accounted for about 70% of the Aleutian North Slope Current in the Aleutian Basin. Two anticyclonic eddies occupied most of the Aleutian Basin along the cruise track. Both eddies extended to the bottom.

The electromagnetic interferences in low voltage secondary cable caused by short circuit fault were analyzed from two main routines coupling through CT and generating through grounding system, which would destroy control system and lead the main power apparatus damage. The calculated results were discussed.

The electromagnetic environments (EMEs) of planned Zhongguancun Software Park near transmission lines, including electrical field, magnetic field and grounding potential rise under three cases of lightning, normal operation and short circuit faults, are assessed by numerical analysis. The power frequency electromagnetic environments of the software park are below the maximum ecological allowed exposure values for the general public, nevertheless the power frequency magnetic field may interfere with the sensitive computer display unit. The influence of short-circuit fault in two different cases of remote short-circuit and neighboring short-circuit on the software park was discussed. The main problem we must pay attention to is the ground potential rise in the software park due to neighboring short-circuit fault, it would threaten the safe operation of electronic devices in the software park. On the other hand, the lightning strike is a serious threat to the software park, protective countermeasures should be adopted to improve the electromagnetic environments of the software park.

Adopting insulated conductors and compact configuration has become the tendency in the renovation of distribution network in China. Advantages of compact configuration are discussed. Superiority of compact configuration against lightning protection has been analyzed. The reason that breakage faults occurred on compact distribution tine with polymeric spacer is discussed. It is due to the bad pollution flashover performance of the polymeric spacer cast with polycarbonate. Polycarbonate Is not suitable for outdoor Insulation. A new triangle composite spacer, which Is suitable for heavy pollution areas, Is designed to prevent breakage faults caused by leakage current. 28 cm is chosen as phase spacing. The application effects of the developed composite spacers are very good.

A circuit model with lumped time-variable parameter is proposed to calculate the transient characteristic of a grounding system under lightning current, which takes into consideration the dynamic and nonlinear effect of soil ionization around the ground electrode. The ionization phenomena in the soil are simulated by means of time-variable parameters under appropriate conditions. The influences of soil parameters, location of feed point, and shape of the lightning Impulse current on the transient characteristic of grounding grids are discussed. The generated electromagnetic fields in the substation are analyzed by using electrical dipole theory and image theory when the lightning current flows into the grounding system. The influence of soil ionization on the electromagnetic fields is presented.

This paper analyzed the principles of the electromagnetic interferences in low voltage control cable caused by short circuit fault from two main routines, coupling through current transformer (CT) or capacitor coupling transformer of voltage (CCTV), and generating from grounding system, their respective calculating methods are presented in this paper. Also the potential difference of the internal core and the shielding sheath at the cable terminals are calculated as an example, and the influences of the soil resistivity, the burial depth and the length of the control cable are considered. It is concluded that the interference voltage and current on the control cables caused by short circuit fault must be paid attention to by electric power engineers, since accurate operations of the metering, control, and protective equipment in the substation relies on dependable input signals.

500 kV polymeric ZnO surge arresters for a compact transmission line against lightning were developed and have been put into operation. The design of the arrester unit and the series gap are discussed. The calculated results states that the line surge arrester can highly improve the lightning withstand level of compact transmission line, and the line arrester can withstand the effects of lighting.

The Kuroshio Extension system links to North Pacific climate through its role in subtropical-subpolar exchange, the formation and distribution of mode waters, and the intensification of the extratropical storm track across the North Pacific. The Kuroshio Extension System Study (KESS) offers a window into these processes through integrated measurements of the ocean and atmosphere and through modeling efforts (Figure 1). The northward flowing waters of the Kuroshio western boundary current leave the Japanese coast to flow eastward as a free jet—the Kuroshio Extension. The Extension forms a vigorously meandering boundary between the warm subtropical and cold northern waters.