Ruapehu 1995-96

Falls of volcanic ash on 25 September 1995 caused shorting on high-voltage electrical power lines at the base of the volcano. This caused voltage fluctuations and problems for electrical equipment throughout the North Island. Cleaning of 18 transmission towers and insulators was undertaken on 27 September 1995 by four crews of four men.

The ash was found to be dry and easy to remove. Strain towers were the most affected due to their insulator configurations (horizontally strung). Rainfall on 26 September had washed away ash on the north side of the towers and insulators. It was concluded that normal rainfall would clean ash from structures, conductors, and insulators except the undersides of strain strings. Three strings of insulators were found to have widespread flashover damage but with no electrical problems. After ashfalls electricity generation and supply companies routinely cleaned ash from affected substations.

On 17 June 1996 electricity supplies were disrupted in parts of Rotorua city after an explosion at a local substation caused by ash and water settling on a transformer due to a resident's hosing ash from the roof of a neighboring building.

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Power Supply > Case Studies