Yutaka Goda

Arc voltage characteristics of high current fault arcs in long gaps

This paper describes the arc voltage characteristics of high current arcs simulating fault arcs on 500 kV class transmission lines and the simulation result of the 50 kA rms class fault arcs. A high power arc test was carried out and the arc voltage in a 3.4 m gap and the voltage of the arc jet near the electrode were measured. The voltage gradient of the arcs and arc jets and the voltage-current characteristics of arcs were investigated. The test results showed that the voltage gradient of the arc jet was larger than that of the arc column. The high current fault arc voltages were calculated using numerical arc models and the arc parameters for the numerical arc model of 50 kA rms class ultra high current arcs were investigated. The calculated values were in good agreement with the measured data.

Forced extinction characteristics of secondary arc on UHV (1000 kV class) transmission lines

Secondary arc extinction characteristics on ultrahigh voltage (UHV) (1000 kV) transmission lines by high-speed grounding switches (HSGSs) were investigated using the high-power test facilities of the Central Research Institute of Electric Power Industry (CRIEPI). The extinction time of secondary arcs by HSGSs is compared with the auto-extinction time. The characteristics of arcs initiated in a large gap (6 m) are described. >

Melting and breaking characteristics of OPGW strands by lightning

Some strands were melted and broken in a 140 mm/sup 2/ OPGW (composite fiber-optic ground wire) in a 187 kV transmission line. It was assumed that this was caused by a lightning strike. DC arc tests simulating lightning strikes were carried out, and the melting and breaking characteristics of OPGW strands were obtained. The electric charge of the lightning strike that damaged the OPGW was estimated from the number of strands broken by the DC arc. In this paper, the DC arc test results, and the test conditions required to simulate a powerful lightning strike are described.

Insulation recovery characteristics after fault arc interruption on UHV (1000 kV class) transmission lines

The insulation recovery time after arc interruption must be known to select the adequate reclosing dead time of rapid auto-reclosing on transmission lines. In order to study insulation recovery characteristics after arc interruption on UHV (1000 kV class) transmission lines, many tests were carried out using the high power test facilities of CRIEPI. In this paper the authors describe the experimental results of these tests of insulation recovery characteristics after arc interruption of UHV transmission lines, and some factors influencing these characteristics. >

Insulation recovery time after fault arc interruption for rapid auto-reclosing on UHV (1000 kV class) transmission lines

The insulation recovery time after arc interruption must be known in order to select an adequate reclosing dead time of rapid auto-reclosing on transmission lines. The flashover probability of the insulation recovery voltage obtained from the insulation recovery tests using full size insulator assemblies was calculated. The insulation recovery time at the fault point for rapid auto-reclosing on UHV (1000 kV class) transmission lines was estimated. >

Development of lightning-resistant overhead ground wire

Overhead ground wires (GW) are vulnerable to strand breakage due to lightning strikes. With the wider application of composite fiber optic ground wire (OPGW), it becomes more important to protect GW from such damage. In this paper, the authors present the results of various investigations made in developing lightning-resistant GW/OPGW. Investigations included field experiments using rocket-triggered lightning, studies on materials and designs to improve lightning characteristics and various evaluation tests, such as DC arc tests, of several prototypes. As a result, the authors have developed lightning-resistant GW/OPGW applicable for conventional transmission lines. >

Development of an EMTP Simulation Model of Arcing Horns Interrupting Fault Current

Arcing horns interrupting fault current is a new type of arcing horns installed on transmission-line towers, which act to interrupt fault current independently within one cycle of commercial frequency. In this paper, we have developed an Electromagnetic Transients Program (EMTP) simulation model of the arcing horns interrupting fault current to ascertain the application effects and devise an installation strategy. The EMTP simulation model can consecutively simulate the entire process, from fault occurrence to fault clearing, by integrating two different kinds of macroscopic arc models, and is capable of dealing with the entire short-circuit current range by taking into account the characteristics of the arc parameters. Finally, we have verified the validity of the EMTP simulation model by comparing simulation and experimental waveforms, and have shown the simulation of current and voltage waveforms in the event of a system fault by using the Japanese Power System Model as an application example of the EMTP simulation model.

Development of a Method of Calculating the Melting Characteristics of OPGW Strands Due to DC Arc Simulating Lightning Strike

Some strands of composite fiber-optic ground wire (OPGW) are sometimes melted and broken by high-energy lightning strikes. DC arc tests simulating lightning strikes have been performed to obtain the melting and breaking characteristics of OPGW strands. The tests have to be performed under many conditions concerning the arc (e.g., current, duration, polarity, gap length) and the OPGW (e.g., size, type, and number of strands) to clarify the melting and breaking characteristics of the strands. In this paper, the calculations regarding the melting characteristics of strands are performed considering the transferred heat and its area from the arc to the strands under the aforementioned conditions. The melting characteristics of strands are calculated with an arc current of 1-100 kA considering the measured current of actual lightning. The calculation results of the strand melting duration depending on arc current show good agreement with the experimental values obtained in dc arc tests.

Analytical investigation on OPGW strands melting due to DC arc discharge simulating lightning strike

Some metal strands of OPGW (composite fiber-optic ground wire) are sometimes melted and broken by lightning strikes. DC arc tests simulating lightning strikes have thus been performed to obtain their melting and breaking characteristics. In this paper, calculations regarding these melting characteristics are performed considering the transferred heat and its area from the arc to the strands. The melting characteristics of strands are calculated with an arc current of 0.1 - 100 kA, considering the current prescribed in the IEC standard and the measured actual lightning current. The calculation results of the strand melting duration depending on the arc current show a good agreement with the experimental values obtained in DC arc tests.

Novel Arc Ignition Method Through Pre-Arc for Power Arc Tests

Metal ignition wires are widely used in power arc tests on insulator sets and similar. Finer metal ignition wire is preferred from the point of view of influence on the apparatus tested. However, if the metal ignition wire is too fine, the arc cannot be sustained. To perform a power arc test successfully, therefore, the metal ignition wire needs to have some degree of thickness. With these requirements in mind, we proposed a novel arc ignition method that allows the use of an extra fine wire by leading to the pre-arc in a current of several dozen amperes. In this paper, the sustainment characteristics of arc ignited from an extra fine copper wire using this novel method were investigated with a gap between the rod electrodes. The results showed that the kiloampere-class arc with a gap length of meter class could be ignited through pre-arc from the copper wire that is 0.03 mm in diameter with a voltage of 12 or 24 kV. The influence of the copper wire thickness on arc characteristics was also studied by comparing the arcs ignited by this novel method with those ignited by the general method where copper wires exceeding 0.3 mm in diameter were used.