Kittipong Tonmitra

The Flashover Phenomena due to Water Drops on Insulating Surface under DC Electric Field

This paper presents the flashover between the electrodes conducted the current by the water drop on insulating surfaces. It causes ageing to the insulator and leads to deterioration when the insulator is used for over years. In the experiments, epoxy resin with the water drop is tested by using direct current until flashover of 70 kV. Besides that, the effect of the water volume, the number of the water drop and the water types - tap and aqua water on flashover are investigated. The flashover of tap water grows faster when increases the volume of water drop. The flashover of aqua water does not depend on the volume of water drop. The deformation and elongate of water drop is in the direction of electric field line. The results lead to protect the damage of insulator caused by the humidity and the loss of their efficiency insulators.

Investigation on Magnetic Properties of L10-FePt/Fe Graded Media Multilayer

To improve writing capability of high magnetic anisotropy medium - L10-FePt, graded medium multilayer is one key candidate. Therefore, investigation of magnetic material properties of graded media multilayer is essential. In this work, we focus on magnetic properties of L10-FePt/Fe graded media multilayer such as hysteresis loop, magnetic energy and magnetic domain by the micromagnetic simulation the object oriented micromagnetic framework software based on the Landau - Lifshitz - Gilbert equation. The graded media multilayer can achieve reducing the switching field, Hsw, below available writing head field with high thermal stability. The anisotropy energy in graded media is higher than single layer and bilayer media that results in unstable magnetization in preferred direction. The proposed graded (f) and (g) structures are high grading magnetocrystalline anisotropy constant, Ku, that can reduce Hsw below single layer, bilayer and available writing head field. The hysteresis loop of low grading Ku structures has different steps; however, it disappear with high grading Ku structures of graded (e) - (g) structures. They have narrow loop compared with single layer. The results from this work lead to improve magnetic trilemma issue and increase data density.

Impact of pin Type Insulators on Power Distribution Networks Caused by Lightning Impulse Overvoltage

The impact of pin type insulators may cause from the lightning impulse overvoltage that hits directly to them. To investigate this problem, this work applies the ATP Draw version 5.6 software to simulate the effect of pin type insulators. Therefore, the obtained results are showed that pin type insulators at pole P4 is closely the lightning strike point, has affected more than the poles P3-P1 and P5-P7. In addition, the conductor has been taken by the heat of over current flow through on it. The flashover and breakdown severity is on insulator upon the distance of them.

Distribution Automation in Case of Tie Bus between Two Feeders at Donekoy Substation in Laos

This paper proposesthe coordination between recloserandfuse link, reclosertorecloser, and recloserwith over current relay in tie feeder 1, 2ofDonekoy substationin Laos PDR.Disilent power factory software is used for simulation toimprove the operation of protective devicesand analyze the operating timein the distribution system.The operating coordination of recloser, fuse and overcurrent relayis improved. Resetting their functionality to limit the fault,the coordinating power aimsto reduce the problems of outages on distribution and also makes the system reliability.In case of maintenance circuit breaker, the 22 kV - tie bus applies to loads feeder 2 to ensure the stability power to appliances load of customers.Therecloser3 was installed on feeder 2 to protect the faults,and coordinates with recloser2 while the short circuit occursat fault2.

Study on Partial Discharge with Water Droplets on the Circular Epoxy Resin Insulator under AC Electric Field Stress

The partial discharge on the insulator surfaces usually occurred in the distribution system. The influence of water droplets is investigated in this paper. This experiment used a circular resin specimen under High Voltage Alternating Current (HVAC) field stress that was applied to the electrodes with a diameter of 2 mm and with a distance between both electrodes of 35 mm. For this methodology, both a single droplet and also double droplets were used on surfaces and the voltage level was adjusted by 15 kV. Results showed that, firstly, the corona phenomenon occurred around the circular electrode after the water droplets on the specimen surface were stretched to each other, but the double drops took a lower voltage level for the stretching than the single drop. In addition, the double drops acted as a bridge, allowing an electrical field to be generated from both electrodes. This pulled them, easily resulting in arcing. In conclusion, water droplets are a main factor to the aging that occurred on the insulators surfaces and this effect is presented in this experiment.

The Effects of Magnetic Properties of L10-FePt/Fe Based Exchange Coupled Composite Media on Switching Field

The L10-FePt/Fe based exchange coupled composite (ECC) bilayer media is one candidate to extend the areal density of magnetic recording system and solve writability issue in trilemma. L10-FePt is the great high magnetic anisotropy material. Therefore, the magnetic parameters of this material such as magnetocrystalline anisotropy constant, Ku, saturation magnetization, Ms, and exchange coupling between a soft/hard interface, are important on magnetic material properties. In this work, the effects of magnetic parameters on magnetic properties of L10-FePt/Fe based ECC bilayer media are simulated by the object oriented micromagnetic framework based on Landau-Lifshitz-Gilbert equation. The ECC bilayer media can reduce switching field, Hsw, of media lower than available writing head field. Hence, writability issues of high Ku media can be achieved. Reducing Hsw of ECC bilayer media obtains from lower Ku and higher Ms values. This work can achieve writing capability of a future magnetic recording system.

Time-Coordination-Based Fault Protection System for Power Distribution Network

In this paper, we present our study of the 22 kV power distribution network at Sisaket substation in Vientiane. Based on the simulation using Digsilent power factory software (DPFS), the protection device, particularly fuses and the reclosers, can be coordinated in time to better protect the system against both temporary and permanent faults, and consequently, the reliability of the system can be improved. Furthermore, the saving fuse and choosing the new protection device to prevent the distribution network is considered in this paper.

100 Millimeters Sphere-Gap with Non Uniform Field Electrodes Triggered Gaps

A common field distortion triggered spark gap utilizing geometric field enhancement at sharp edges usury operates in a cascade mode via the trigger electrode. A new trigger concept is propos this research allowing strong non-uniform electric field enhancement with output precision voltage by holding-off DC voltage ranging from 1 to 135 kV and direct breakdown between the two main electrodes. A test setup was designed to testing with four modes of operation as mode A, B, C and D to prove the feasibility on this concept. Were result experimental r the recommended mode of operation is mode A and mode D considered to be unsatisfied to most applications. The best results achieved by using the triggering with mode A at a wide precision designed breakdown voltage range 1-120kV with a minimum percentage ratio of Fire/Self-fire Voltage lower to 36-47%

The Influence of Nanofilled Aluminum Oxide on Electrical Tree Growth Behavior under High Voltage Non-Uniform Field Stress

This paper proposed a study on solid insulator that can withstands the high electrical field stress. In order to clarify how the solid insulator can withstands the high electrical field stress, an Araldite epoxy resin with specific amount of nanoAluminum Oxide (Al2O3) filler have been chosen for the experiments. The influence of nanoAluminum Oxide (Al2O3) filler on the electrical tree propagation has been investigated. The electrodes of point-plane geometry were impregnated into the sample and tested under high voltage AC. The level of applied voltage was 12 kV (AC), 50 Hz. The results of experiment showed that the specific ratio of nanoAl2O3 (0.1 wt% to 0.3 wt%) filler can inhibit the growth of the electrical tree as well as it can withstands the high electrical field stress.

Solid Dielectric Barrier in Oil Insulator under Uniform and Non-Uniform Electric Fields

This paper presents the dielectric barrier (PVC, PMMA, and glass) breakdown voltage test in transformer oil in uniform field, slight non-uniform field and highly non-uniform field generated by plate-plate, plate-point, and point-point electrodes, respectively. It was found that PVC can withstand the maximum breakdown voltage that is higher than PMMA and glass. The dielectric barrier with 1 mm thick placed next to the high voltage electrode and ground electrode can withstand the higher breakdown voltage than dielectric barrier with 2 mm thick placed next to the ground electrode and at the middle of electrodes. PVC for point-point, plate-point and plate-plate electrodes can withstand the maximum breakdown voltage of 216.5, 195.7 and 181 kV, respectively. The breakdown voltage of solid insulations is different because of the shape of electrode. These results lead to design the solid insulator in transformer oil under uniform and non-uniform electric fields.