Hydropower Monitoring Solutions
Modern grid issues, old age and flex-ops have brought numerous new problems to the hydropower industry. A comprehensive monitoring system is the best way to stay ahead of the curve. While hydroturbine equipment can be quite stout, excessive start-stops, running loads outside design parameters, cavitation, rim float, and structural issues are becoming the norm, causing cumulative damage in the turbine-generator assembly.
The full suite of Suprocktech sensors and telemetry work in concert with existing plant systems scanning for changes in operating states that could lead to potential issues, giving operators the peace of mind they need to make it to the next scheduled outage.
TDMS Turbine Dynamics Monitoring System
All rotating generating machinery is susceptible to high cycle fatigue (HCF) due to torsional vibrations. It has been well documented in theory and observation that negative sequence currents caused by electrical grid faults, mal-synchronization, and other stochastic grid perturbances are the main cause for cumulative torsional vibration damage. It is a driving parameter for rotor-train design and life extension modifications. However, the limitations of contemporary sensor technology made it difficult to record both real-time and long-term data. The TDMS system employs wireless power and data enabling long-term monitoring of torsional vibration through high-sample strain and acceleration measurements. Advanced sensors gathering long-term and real-time data during grid transients is an extremely valuable tool plant control systems can use for risk-mitigation and equipment life extension.
Suprock Technologies has built and installed the instrumentation required to obtain and collect torsional vibration measurements from the turbine-generator. This instrumentation includes the TDMS system and applicable measurement telemetry that directly relates to the vibration of the turbine-generator system.
Increased start-stops and running at loads outside turbine design parameters is causing increased issues with cavitation in hydroelectric plants. Cavitation damage is cumulative and can lead to runner cracking and severe erosion if not properly monitored. Sensors to detect cavitation require extreme sensitivity due to physical limitations where instrumentation can be practically located.
The system must help discern between inlet leading edge cavitation due to its erosive capability, bubble cavitation at the outlet of the blades because it affects the efficiency of the turbine, and the draft tube swirl that limits the stability of the turbine operation. The approach is inclusive of all manifestations of cavitation, as different forms of cavitation may be seen throughout the operating states of the turbine. Multiple measurement locations are also chosen to apply sensor voting and eliminate false positives. The ability to understand types of cavitation is important for any post-monitoring economic assessment and/or condition-based monitoring of cumulative damage.
The system is capable of discerning different types of cavitation such as:
- Leading edge cavitation
- Travelling bubble cavitation
- Draft tube swirl
- Inter-blade vortices cavitation
Rim Float Monitoring
Hydroelectric assemblies are rather stout and can run with minor float issues but as the problem worsens it can lead to an irregular air-gap, key fretting, accentuated magnetic forces between the rotor poles and the stator winding, fatigue, loss of rotor center, balance issues and further deterioration. Given the astronomical cost of unscheduled outages, plant operators need to know if they can keep running safely until the next scheduled outage.
Monitoring rim displacement relative to the spider is a great way to keep an eye on rim float as the problem progresses. Our new rim displacement sensor based on our strain and wireless power technology has the ability to detect displacement continuously with resolution down to 8nm. More than enough to detect changes in overall displacement that could be a sign of problems to come, giving operators the peace of mind they need to make it to the next scheduled outage.
Auxiliary Systems and Structural Sensors
Both alone and correlated with torsional vibration data, strain sensors on gate actuators produce valuable signals. Higher than normal average forces can expose issues such as mechanical binding, uneven operation, or detecting obstructions.
Vibration data from gate strain sensors can be correlated with torsional vibration data to determine whether torsional vibration phenomena is being caused by a gate related anomaly or self contained in the TG section.
Aging infrastructure and the variable nature of concrete is bringing new-found issues to the hydropower industry.
High bandwidth strain sensors are perfect for correlating abnormal operating phenomena with structural issues. In one case, an intermittent torsional vibration issue with potential damage to the runner was identified to be an issue with a shifting foundation. Measured scroll case strain and foundation strain was found to be higher any time the problem appeared. The shifting foundation was pinching the scroll case, putting more stress on the unit’s bearings.
Software & SCADA Integration
Caron Engineering’s DetectIt software has been configured to accept data from all Suprocktech sensors and synthesize the high speed data into actionable information that can be fed directly into the plant’s SCADA system.
Analyzers will be provided to perform the following functions. These analyzers are based on existing Dtect-IT capabilities:
- Limit analysis.
- Frequency bin tracking. (tracking energy over time).
- Versus analysis (correlated sensor analysis, for example comparing TDMS to stationary sensors.)
- Accept a user defined arbitrary number of frequency “bands” in which the following parameters are calculated:
- Area under the FFT within each band. (integration/energy)
- Peak magnitude frequency present within each band.
- Amplitude of the peak frequency in each band.