2012-04-24 - Mighty River Power, with ABB’s support, is leading the way in Hydro generation dam safety management following the recent completion of the new fully automated Whakamaru and Maraetai stations’ spillway controls upgrade projects.
Background
Both stations are part of the wider controls upgrade programme of Mighty River Power spillways, located at their Waikato River dams. The programme is designed to further improve the reliability and robustness of spillway operation, hence increasing safety to both the dam infrastructure, and the wider community.
The Waikato River plays a large part in New Zealand’s power generation being able to produce approximately 10% of the country’s capacity. There are nine power stations situated on the Waikato River all owned and operated by Mighty River Power – Maraetai (with two stations) being the largest of these with a capacity of 360MW, and Whakamaru somewhat smaller with a capacity of 98MW but a critical station in the hydro power chain.
Maraetai power station 2 and spillway exit point
Mighty River Power required a spillway gate control system that met comprehensive safety review recommendations and was entirely independent of the station control. Full automation of the control system was an existing feature that needed to be retained and enhanced, ensuring that the spillway can still function unmanned in case of an extreme event where all power and communications are lost between the spillway and the wider powerhouse. Mighty River Power required increased redundancy in lake level monitoring, with the addition of a failsafe trigger system.
ABB’s solution
Working with AECOM on the design, ABB installed a new system with a dedicated spillway PLC and is totally independent of the station control. ABB’s service experience allowed the installation of the panels at both sites simultaneously, shortening the overall lead time on delivery. The installation was integrated into Mighty River Power’s existing system with minimal disruption, as ABB leveraged knowledge gained from previous experience assisting with design and installation of panels for the Atiamuri spillway controls upgrade.
Mighty River Power praised ABB, commenting that the company showed good initiative throughout the project, maintained strong relationships with project staff and delivered a high quality of workmanship.
Maraetai control panel building and hydraulic gate system
The new system creates multiple levels of redundancy supporting the existing functionality of remote spillway operation from Mighty River Power’s Hamilton or Auckland control centres, or through automation as a stand-alone site at the spillway structure. Functionality has been enhanced through the installation of a new system using analogue transducers to replace limit switches to the lake level and spill gate position indication – this avoids a single point of failure, improves redundancy, diversity and overall reliability.