Modeling of time of arrival method for lightning locating systems

Various methods are used to locate cloud-to-ground lightning flashes. Even though a higher cost is incurred, a network of sensor stations is preferable to a single station due to the improved accuracy. For a single station measuring system, the accuracy of its analyses is mostly based on the chosen mathematical equations which can be solved in either linear or nonlinear mode. The sensitivity of the measuring equipment used is also particularly significant. This paper concentrates on the modelling of time of arrival (TOA) technique for locating a lightning flash by utilizing three broadband antennas. Consequently, by employing the developed model, the influences of geometric parameters on the accuracy of the model are evaluated. Therefore, a Matlab based simulation of the measuring system is developed. In the developed codes, randomly located lightning flash with its corresponding electromagnetic radiation was modelled. Results show that parameters such as lightning path shape, distance of the leader, and leader location can directly affect the accuracy of the TOA technique for extracting the azimuth and elevation

Lighting locating system by using time of arrival technique and three broadband antennas

Lightning locating system is an active research field in high voltage and high current applications. The lightning discharge processes radiate electromagnetic wave in broadband range of VLF through UHF. In the stepped-leader progression, stepped leader radiates electromagnetic field while it progresses. In this project, the location of lightning was estimated by using radiated electromagnetic field and employing the Time of Arrival technique (TOA). The measuring system was implemented at IVAT and lightning events were recorded for a period of about six months. The proposed system uses three broadband antennas perpendicular to each other to roughly estimate the azimuth and the elevation of lightning strikes. Two short base lines used in the system have a distance of 14.5 meters between them. Experimental results and signal simulations show that the system has a good accuracy for the detection of the azimuth and the less accuracy for the elevation. The simulation and reconstruction of lightning strikes has also been done by using the Lab View program

Simulation of lightning flash and detection using time of arrival method based on four broadband antennas

Various methods are used to locate cloud-toground lightning flash. The accuracy of the methods depends on the number of sensor stations, station topology, mathematical model adopted for the analyses, and the type of measuring equipment. For a single station with the configuration of short baseline in a measuring system, the accuracy of analysis is mostly based on the chosen mathematical equations (and assumptions) which can be solved in either linear or nonlinear mode. This paper concentrates on the simulation of a lightning flash and its detection based on the Time of Arrival (TOA) method by utilizing four broadband antennas. The accuracy of the TOA method is also evaluated in this work. A Matlab based simulation of the measuring system is implemented to construct a randomly located lightning flash with its corresponding electromagnetic radiation. Then, suitable mathematical models used as measurement systems based on the 3-antenna TOA method to determine the azimuth and elevation angles, which in turn can be used for the calculation of flash coordinates in term of (X,Y,Z) with the help of the fourth antenna. © 2011 IEEE

Effect of ambient temperature on leakage current of gapless metal oxide surge arrester

Zinc oxide (ZnO) gapless surge arresters are used for lightning and overvoltage protection in electrical power system. The leakage current monitoring is one of the well known method for the ZnO surge arrester ageing level determination. However, the ZnO leakage current is known to be dependent on the ambient temperature. This paper aims to study the effects of temperature variation due to ambient conditions on the leakage current of ZnO surge arrester. The effect of a significant increment of leakage current with an increase in temperature may result in a wrong assesment of the ageing level of the arrester. The leakage current of three 120kV rated polymeric housed ZnO surge arresters were measured in a custom made thermally insulated enclosures at varying temperatures. Up to 20% increase in the leakage current was observed with a 20°C increment above the ambient temperature. For a typical variation of ambient temperature in Malaysia in the range of between 30°C and 40°C, the corresponding changes in the leakage current can be up to 11%. The temperature does significantly affect the leakage current measurements used for monitoring of zinc oxide surge arresters. This significant change in the leakage current due to ambient temperature variation can affect the decision in assessing the condition of surge arresters during routine monitorin

Three-dimensional potential and electric field distributions in HV cable insulation containing multiple cavities

Cross-linked polyethylene is widely used as electrical insulation because of its excellent electrical properties such as low dielectric constant, low dielectric loss and also due to its excellent chemical resistance and mechanical flexibility. Nevertheless, the most important reason for failure of high voltage equipment is due to its insulation failure. The electrical properties of an insulator are affected by the presence of cavities within the insulating material, in particular with regard to the electric field and potential distributions. In this paper, the electric field and potential distributions in high voltage cables containing single and multiple cavities are studied. Three different insulating media, namely PE, XLPE, and PVC was modeled. COMSOL software which utilises the finite element method (FEM) was used to carry out the simulation. An 11kV underground cable was modeled in3D for better observation and analyses of the generated voltage and field distributions. The results show that the electric field is affected by the presence of cavities in the insulation. Furthermore, the field strength and uniformity are also affected by whether cavities are radially or axially aligned, as well as the type of the insulating solid. The effect of insulator type due the presence of cavities was seen most prevalent in PVC followed by PE and then XLPE

The effect of magnitude and shape of applied voltage on the partial discharge behavior in cylindrical cavity within a dielectric material

One of the important phenomena which is important in equipment when they are under high voltage stress is Partial discharge (PD). Partial discharge measurement is commonly used to evaluate the performance of the insulation in high voltage system. Modeling of the discharge in insulation can give a better understanding of this important phenomenon. A cavity within a dielectric material is a highly stressed area and the ideal place for starting partial discharge and breakdown. The applied voltage is one of the important factors that PD activity is influenced by that. Previous studies have considered the behavior of PD activity in a spherical cavity at 50Hz of sinusoidal applied voltage. However, still not so much work on the simulation of the PD activity in the cavity under different condition. Also, there is little data are available on the effect of parameters on the PD activity. This paper describes the behavior of PD activity as a function of applied voltage in a cylindrical cavity within a homogeneous dielectric. COMSOL and MATLAB software were used to carry out the simulation based on the finite element method (FEM). The number of PDs per cycle changed with different applied voltage so the highest number of PD at 20kV and the lowest value at 8kV. The maximum PD magnitude is raised from 1200pC at 8kV to 2400pC at 20kV applied voltage. The number of PD is most prevalent for sinusoidal followed by triangular waveform and then sawtooth. Comparison of the simulation results and experimental results are in good agreement. The result can help the researcher to understand more about the characteristics and behavior of partial discharge. Which may help the insulation diagnostic testing or condition monitoring

Localised single-station lightning detection by using toa method

Lightning is an electrical discharge during storms that can be monitored continuously from certain distances. It can be either within clouds (intra cloud), or between clouds and the ground (cloud-ground). There are various techniques used nowadays to locate lightning, and to determine various parameters produced from lightning. Each technique provides its own claimed performances. This paper attempts to provide instantaneous detection of lightning strike lightning location using the Time of Arrival (TOA) method of a single detection station (comprises of four antennas). It also models the whole detection system using suitable mathematical equations so as to give some understanding on the differences between the measured and calculated (theoretical) results. The measurement system is based on the application of mathematical and geometrical formulas. Several parameters such as the distance from the radiation source to the station and the lightning path are significant in influencing the accuracy of the results (elevation and azimuth angles). The role of each parameter is examined in detail using Matlab. This study solved the resultant non-linear equations by Newton-Raphson techniques. Methods to determine the radiation source which include the exact coordinate of a given radiation source in 3-dimensions were also developed. Further clarifications on the cause of errors in the single-station TOA method and techniques to reduce the errors are given

Investigation of ferroresonance mitigation techniques in 33 kV /110 V voltage transformer using ATP-EMTP simulation

Ferroresonance is a complex nonlinear electrical phenomenon that can cause dielectric and thermal problems for electrical equipment. Electrical systems with ferroresonant behavior are nonlinear dynamical systems. The ferroresonance phenomenon may take place when the core of an inductive device becomes saturated, and its current flux characteristic becomes nonlinear. While in the case of a linear resonant circuit the resonance frequency is well defined, in the case of a nonlinear circuit, the oscillations may exist at various frequencies, depending on many factors of the particular case. In this paper, ferroresonance phenomenon and its mitigation techniques in 33 kV/110 V voltage transformers (VT) were studied using ATP-EMTP simulation. Initial investigations were carried out for the VT failures occurred at one substation in Malaysia. Physical and burn characteristics of the failed VTs were studied. Simulation results show that ferroresonance cannot be proven to have occurred at the VT due to switching operations since one precondition, namely the critical capacitance, could not have been satisfied. However, in the event of a ferroresonance occurring, several mitigation techniques such as using load resistors, proper grounding sequence, reconfiguration of VT connection, and overcurrent and overvoltage protection can be implemented

Modeling of Time of Arrival Method for Lightning Locating Systems

Various methods are used to locate cloud-to-ground lightning flashes. Even though a higher cost is incurred, a network of sensor stations is preferable to a single station due to the improved accuracy. For a single station measuring system, the accuracy of its analyses is mostly based on the chosen mathematical equations which can be solved in either linear or nonlinear mode. The sensitivity of the measuring equipment used is also particularly significant. This paper concentrates on the modelling of time of arrival (TOA) technique for locating a lightning flash by utilizing three broadband antennas. Consequently, by employing the developed model, the influences of geometric parameters on the accuracy of the model are evaluated. Therefore, a Matlab based simulation of the measuring system is developed. In the developed codes, randomly located lightning flash with its corresponding electromagnetic radiation was modelled. Results show that parameters such as lightning path shape, distance of the leader, and leader location can directly affect the accuracy of the TOA technique for extracting the azimuth and elevation

Surge arrester leakage current analysis by using particle swarm optimization technique

Surge arresters, as protective equipment, are used to limit any overvoltage in a power system resulting from various sources. The surge arrester affects from degradation due to the continuous operating voltage system as well as due to repeated lightning current discharge. Therefore, condition monitoring and health diagnostics of surge arresters are a necessary issue. Hence, as a feasible solution, a condition monitoring based on leakage current measurement techniques was selected to tackle the problem of age diagnostics of surge arresters. The Particle Swarm Search Algorithm was introduced as a method for extracting the third harmonic resistive component, Ir3rd, from the total leakage current. To employ this method for extracting Ir3rd, codes were developed in Matlab. The setting of Particle Swarm Search Algorithm was configured for extracting Ir3rd and accuracy of 94% was obtained