Condition Monitoring of Hydroelectric Plants

Douglas Morris Mining and Power Industries Sr. Manager

Douglas Morris
Mining and Power Industries Sr. Manager

Author: Douglas Morris
Things are not getting easier for the power industry as it experiences increasing complexity with dispatching generating units. Because dispatching is determined by a host of factors including cost, demand, transmission, environmental constraints and unit availability, the dispatch stack at a typical utility is different when compared to years ago when renewable power was virtually nonexistent. Since variable cost from operations is the primary dispatch driver, renewable, nuclear and hydroelectric assets are usually the preferred baseload choice.

Keeping these assets available is critical to the profitability of utilities. For this post, I’m going to address the needs of those companies that have hydro plants in their portfolios.

Source: U.S. Energy Information Agency, Electric generator dispatch depends on system demand and the relative cost of operation, http://jimc.me/1qaICmw

Whether at lower loads where cavitation can occur, or at full load, hydro turbines are subject to large stresses which eventually lead to mechanical problems. If developing problems are unknown and left unchecked, an unplanned outage will occur. As a result, machinery health monitoring is recommended to minimize downtime and keep repairs within the window of planned outages. This is easier said than done. Because hydroelectric turbines operate at low speeds, with faults appearing as low as 0.5 Hz, analyzing the health of the unit requires special monitoring hardware capable of detecting these extremely low frequencies. The objective is to detect underlying problems early and integrate turbine health data into a control system which allows a plant to address issues before they affect production. Emerson technology works well for as these low speeds and frequencies and can help utilities with early detection of the following:

  • Imbalance
  • Misalignment and coupling
  • Cracked or chipped blades and shaft
  • Inadequate lubrication of mechanical parts
  • Cavitation erosion on the impellers
  • Breakage of wicket gate linkage
  • Rotor rub
  • Rotor bow
  • Hydraulically-induced vibration and imbalance
  • Damaged stator isolation

In order to access these data, a turbine must be outfitted with a combination of sensors and analysis hardware. Here are typical measurement points required for evaluating the health of hydro turbine:

Hydro-Turbine-Machinery-Protection-Measurements

Hydro-Turbine-Machinery-Protection-Measurements-2

Most utilities will use a combination of permanently installed and portable condition monitoring technologies. Regardless of the approach, comprehensive hydro machinery monitoring ensures early detection of developing turbine problems. Those utilities that can detect potential problems early and make critical decisions about whether or not to keep a unit operating will have a competitive advantage.

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