The Ngawha Expansion Project (NEP) involved adding a new power station to the existing Ngawha Generation Limited (NGL) operation at Ngawha. The existing power station consists of three Ormat Energy Convertor’s 1-3 (OEC1-3) which in total produce about 25MW net export at 33kV from Ngawha 1 substation (NGA). The new power station is called OEC4 and will be about 32MW net export at 33kV. Ngawha Transmission Substation (NGT) was required to facilitate the connection of output from OEC4 plant, to the 110kV Grid at Kaikohe 110kV Substation. Provision was also made for future expansion to connect a further plant ‘OEC5’.
Ergo has a long term and continuing involvement at Ngawha, including being responsible for the design of the new NGT 110kV substation. The substation comprised a 110kV switchyard, initially of an incoming line bay, and a 110/33kV transformer bay along with a new building housing the 33kV switchgear and control panels. Full civil and structural design was undertaken, along with electro-mechanical calculations associated with the 110kV Air Insulated Equipment. The main challenge with this project was fitting the switchyard onto a limited pre-prepared platform. We adjusted equipment spacing to ensure the solution was both operationally acceptable and able to be safely maintained.
The scope of services also involved conceptual design, primary equipment specifications, civil and electrical detailed design, protection study and settings, earthing studies, MV/HV cable studies, and civil construction monitoring.
The project was energised on schedule and is now available for connection from the new geothermal power plant, once commissioning has been completed.