The refurbishment of electrical plant operating in a geothermal power station

In 1983, four HP turbogenerators were de-commissioned, after 25 years continuous service, from the Wairakei Geothermal Power Station in New Zealand due to the ongoing decline in geothermal steam pressure. Two of these machines rated at 12 MW have undergone extensive refurbishment to fit them for a new life at the Ohaaki Geothermal Power Station, which is being constructed. The authors outline the steps taken by the Electricity Corporation of New Zealand to assess, test and refurbish the generators, generator exciters, power transformer, circuit breakers and associated electrical auxiliaries from decommissioning at Wairakei to installation and commissioning at Ohaaki. The measures adopted to improve the control and protection of the units for incorporating into a modern unmanned power station are given. Environmental considerations necessary to avoid hydrogen sulphide corrosion of electrical plant are outlined