Gilkes completes work on Washington hydro schemes

12 July 2017

Gilkes has completed work on two hydropower schemes for the Washington County Water Conservancy District (WCWCD) in the US.

The company was responsible for modernisation of equipment at the Hurricane and Quail Creek hydroelectric projects.

The Quail Creek project features a 38” twin jet high capacity Turgo impulse turbine. It was originally supplied to WCWCD in 1984. In 2014 Gilkes visited the site with a view to proposing upgrades to the original control system which was due for replacement. The original hydraulic governor had become unreliable and operators had concerns about the system completing shutdowns in fault condition. The controls had also lost its automatic function meaning restarts required operator attendance and manual synchronising. Gilkes was then commissioned to update the turbine governing and controls with a bespoke package.

A new hydraulic control module was supplied to provide control of a new hydraulic ram attached to the deflectors. The new hydraulic power unit features accumulators for storing hydraulic pressure. In the event of a loss of ac supply the pressure from these will be used to close the turbine deflectors removing water from the runner and ensuring a safe shutdown of the system.

Attention was given during the design phase to integrating the new controls with the existing system. Installation in the existing cubicles was preferred to give the tidiest powerhouse layout and make use of the existing space. The controls were manufactured on new back plates and doors that were secured into the existing cubicles. Pre wired sockets provided speedy interconnection between the different parts following installation.

An uninterruptable power supply was also included to provide backup power for the spear valve actuators in the event of a loss of mains supply.

The new controls package returned the plant to fully automated operation. The system can automatically start the turbine, synchronise the generator and generate according to the amount of water available at the intake. The control system is continuously monitoring the health of all aspects of the turbine and generator. Should any fall out of tolerance then an automatic shutdown is issued to protect the plant. Depending on the severity of the fault operators are automatically alerted via email and the WCWCD SCADA system.

With the Quail Creek plant returned to fully automatic operation operators anticipate increased generation and reduced downtime. They are now able to focus on other duties and attendance monitoring and supervising the turbine is now dramatically reduced allowing them to be more productive maintaining other parts of the infrastructure.

At the Hurricane hydroelectric plant, Gilkes was invited to review the plant’s system with a view to upgrading the control system and governor to improve reliability following 30 years of operation.

The mechanical aspects of the turbine were found to be operating in good condition despite constant attack from the sediment laden water abstracted from the river. The Turgo turbine has a reputation for excellent abrasion resistance and this was in evidence here. Many parts that are in constant contact with the water are still originals from when the turbine was supplied. The superior resistance to wear of the Turgo compared to other turbine types and the regular inspections and maintenance from operators has meant the turbine can expect to provide reliable duty for many years to come.

The original spear valve actuators had become unreliable and frequently needed maintenance, therefore these were upgraded to modern modulating rotary actuators to provide reliable control of flow through the turbine.

A complete new control panel suite was proposed replacing the existing control and switchgear. The suite was custom designed to fit over the existing cable ducts and to accommodate a roof mounted building services transformer, a bespoke control philosophy was also developed to meet the specific needs of WCWCD. To aid them in meeting outflow obligations, turbine flow control was largely separated from the operation of the generator, which now allows them to pass flow through the turbine while the generator is shutdown.

The deflector control arrangement was completely revised to facilitate the new control philosophy. The original electric actuator was removed and a hydraulic ram put in its place, the ram is operated by a hydraulic control module featuring an accumulator to ensure safe shut down. Control of the deflectors is by a new digital governor, which works to precisely match the generators speed to the grid prior to synchronisation. Generator start up is now possible at any turbine flow rate above the minimum flow of the system, including at full turbine flow.

The new control system is fully automated and is expected to improve the annual energy production of the generator significantly, due to higher reliability and lower operator dependence.



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