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Overhauling the Snowy Scheme

Upgrading the legacy control and information system of Australia’s Snowy Mountains Hydroelectric Scheme presents challenges on many fronts. Rockwell Automation’s project engineering group has carved out a solution based on alliance-style cooperation and a commitment to the long term.

Located in Australia’s Southern Alps, the Snowy Mountains Hydroelectric Scheme was built between 1949 and 1974 to provide water for irrigation and electricity from hydroelectric generation. This ‘engineering wonder of the world’ incorporates a massive volume of water flowing through 16 major dams, 145 kilometres of interconnecting tunnels and 80 kilometres of aqueduct--as well as two pumping stations and seven hydroelectric power stations.

Comprising a total of 31 generators, the Scheme’s power stations have a combined generating capacity of 3756MW and provide the Australian national grid with an average of 4500GWh of ‘clean’ renewable hydro electricity per annum.

In 2005, to meet modern demands, owners and operators Snowy Hydro embarked upon the Scheme Modernisation Project: a seven-year, A$250 million upgrade that is the Scheme’s first major overhaul. A key element of this is the complete replacement of the control, protection and governor systems, HV circuit breakers and generator excitation systems. In an alliance-style relationship, Rockwell Automation’s project engineering group has linked arms with the Snowy Hydro team to tackle the control systems overhaul.

The controls upgrade included the replacement of legacy relay logic controls and analogue gauging, with state-of-the-art PAC and electronic operator interface technologies.

Information is empowerment
The controls and information systems in each Snowy power station support a multiplicity of ancillary systems that are associated with each of the 31generator/turbine assemblies (‘units’) and the two pumping units. These include cooling water, lube oil and hydraulic oil, along with the monitoring of bearing and winding temperatures and other unit diagnostics.

According to Darryl Eager, Snowy Hydro’s manager controls technology, the upgrade is important for both maintaining reliability and collecting real-time operational information. “By collecting as much operational information as possible, we can leverage it to our advantage. Information is empowerment for any sort of improvement,” he says.

In simplest terms, the controls upgrade aims to replace the 1960/1970 relay logic controls and analogue gauging with state-of-the art programmable automation controller (PAC) and electronic operator interface (EOI) technologies.

The first of the 33 unit control upgrades was undertaken in 2005 at Tumut 3 (T3) power station, which established the ‘proof of concept’. A ‘standard’ unit control architecture was developed, featuring two Allen-Bradley ControlLogix PACs (one for the unit’s governor and the second for the remainder of the turbine/generator), plus a third for the transformer associated with each pair of generators. It also included a PanelView Plus 1500 EOI for local control and monitoring, and an Allen-Bradley Powermonitor 3000 power quality and sub-metering monitor to collect and monitor critical generator power parameters.

The architecture is founded on a ‘DeviceNet/ControlNet/EtherNet/IP’ communications structure. Device-level DeviceNet communications links the controller to generator floor devices, including Allen-Bradley E3 Plus intelligent motor protection, and Allen-Bradley XM series temperature modules. Dual-redundant ControlNet communications links the controller to remote I/O chassis, the PanelView Plus EOI and Powermonitor 3000, while EtherNet/IP facilitates controller monitoring and maintenance, together with unit-to-transformer and unit-to-unit communications.

Communications clincher
An essential part of the project was the ability to realise Distributed Network Protocol (DNP3) connectivity with Snowy’s existing SCADA system and protection relays. According to Eager, this clinched the selection of the ControlLogix platform. “ControlLogix could offer a DNP3 solution that worked with our SCADA system, whereas the other controllers really couldn’t,” he says.

While ControlLogix was a key attraction, Eager notes that the ‘Integrated Architecture’ approach has brought many benefits. “Everything is driven by the same Rockwell Automation software tools, it all has the same look-and-feel, and this really helps our guys in coming up to speed and maintaining the systems,” he says.

With four unit upgrades complete at end-2008, the project is progressing well. “This is going to be the same upgrade 33 times,” says Eager. “Effectively, what Rockwell Automation has done is automate the automation! The depth they have gone into has provided real advantages.”

Eager says Snowy Hydro has achieved the reliability improvements that were the main goal, plus around ten times the amount of real-time operational data is coming back to the Snowy Mountains Control Centre in Cooma. Importantly, a model that will see the controls upgrade element of the Scheme Modernisation Project successfully completed through to 2012 is now well established.