Modelling for monitoring – When millimetres matter

Author: Renata Barradas Gutiérrez

Pumped storage hydroelectric plants are one of the various ways of extracting energy from water. The biggest hydropower energy sources in Lithuania are the Kaunas Hydropower Plant and the Kruonis Pumped Storage Hydroelectric Plant (KPSHP). The KPSHP is a pillar for the Lithuanian energy system that has been successfully supplying energy to homes and businesses for more than 20 years. Located close to the city of Kaunas, this state-of-the-art energy facility is the one of the biggest plants of its type in the Baltic region.

This 900 Megawatts hydroelectric plant is designed to generate electricity, balance consumption by regulating voltage, frequency and load fluctuations, and compensate energy deficiency in case of an emergency situation. According to Lietuvos Energijos Gamyba, the KPSHP covers 6 per cent of Lithuania’s total electricity demand and is capable of ensuring 94 per cent of the total necessary energy reserves for Lithuania in case of emergency – a deformation in its structure can be fatal to Europe’s Baltic state energy system.

Going high tech for dam monitoring

To monitor KPSHP, UAB SmartOffice surveyed the hydroelectric plant using the Leica Nova MS60 MultiStation to collect measurements and a point cloud of the structure. The 3D data collected allowed UAB SmartOffice to analyse the surface and calculate the verticality of the hydroelectric plant. The model generated with the point cloud will also serve as a reference for future scanning that will monitor the current conditions and deformation of the dam.

“Scanning with Leica Nova MS60 MultiStation has brought more results than expected. Besides 3D scanning up to 1,000 metres, the main benefits were time saving, accuracy and simplicity,” said Jonas Varnas, general manager at UAB SmartOffice. “Using the MS60 was as simple as a routine using a TPS but combining the precision of TPS measurements and 3D scanning into one system.”

With the MS60 MultiStation, complex sites can be surveyed with overlaid measured points and 3D models in one view, allowing users to perform verticality and deformation checks to identify damage and defects in a more reliable, quicker and complete way. The 3D scan capability of the self-learning MultiStation helps users expand their portfolio of offered services, being able to be used for:

• construction monitoring
• quality inspection
• clash detection
• as-built Building Information Modelling (BIM)

The KPSHP was monitored by geotechnical sensors, so no geodetic equipment was used. In comparison to other sensor technologies where deformation information is limited to few points, the MS60 MultiStation provides the ability to measure a dense amount of points and provide the measurement of displacements in relation to millions of points with overlaid TPS measurements.

Inspecting and comparing surfaces

What makes the Kruonis plant special is its ability to operate in pump mode during periods of low demand or as a traditional hydroelectric plant to supply the normal energy demand during the day.

These water level changes in the upper reservoir of the dam can cause deformations. The KPSHP authorities, therefore, were interested in analysing the surface and verticality of the dam, identifying places with deformation and comparing the scanned model with the ideal model.

3D Reshaper, an essential software for surveyors working with point clouds, allowed UAB SmartOffice to measure, inspect and compare surfaces displaying deviation information with millimetric accuracy. The modelled surface generated from the point cloud provided an accurate representation of reality to detect millimetric changes in shape for the entire structure.

“3D Reshaper allowed us to do the best shape export, analyse the surfaces with several integrated tools, and permitted our client to inspect surfaces in a very clear way – exactly what our customer was looking for,” said Varnas.

Monitoring matters

In dam monitoring, millimetre precision is required. The consequences of structural deformations in these structures go beyond multimillion costs. Consequently, deformations should be discovered and monitored in a timely manner to ensure a safe operation and usage, and cost-effective construction and management.