|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1994 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1993 : ¥1,200,000 (Direct Cost : ¥1,200,000)
In the area having heavy volcanic ashfall, the distribution line trouble has been caused. It seems owing to the increase of the leakage current on the insulators polluted by volcanic ashes. We examine the factors which increase the leakage current and decrease the fluctuations of it in order to abate the distribution line trouble caused by the volcanic ashfall. For this purpose, to begin with, the electric characteristics are in detail examined, for example, the chemical compositions of the volcanic ashes and the electric conductivity, the ion concentration etc.of the volcanic ashes solution. Then on these basic data, the dependence of the leakage current on the various conditions of insulators and high voltage cut-out bases and arresters polluted by volcanic ashes is experimentally investigated. As the result, the following matters are elucidated :
1. The leakage currents are increased and in addition the fluctuations of them are increased involving the generation of corona only when t
he ashes accumulated in the ribs of insulators become wet.
2. A combination of the strain insulator with the anti-pollution type insulator restrains the generation of a corona, even if the insulators are polluted by the volcanic ashes. This combination enables us to limit the fluctuations of the zero-phase-sequence voltage and to diminish the service interruption problems caused by the operation of the circuit breaker.
3. The volcanic ashes increases the leakage current in the case of the strain insulator, the high voltage cut-out base and the arrester but littel leakage occurs in the case of the pin insulator.
4. The observation of a corona makes us presuppose that the potential gradient in the ribs of the strain insulator is large.Accordingly, it follows that in order to decrease leakage currents, the strain insulator should be lengthened in the inner-cylinder within the insulator, as well as in the anti-pollution type insulator.
In addition, the policies for abating the troubles also are got such as the determination of the most suitable direction, numbers and insulator types.