Abstract
This paper presents the first application of the Laser Doppler Vibrometer (LDV) in non-stationary conditions within a hydropower plant powerhouse. The aim of this research is to develop a methodology to include non-contact vibration monitoring as part of structural health monitoring of concrete dams. We have performed in-situ structural vibration measurements on the run-of-the-river Brežice dam in Slovenia during the start-up tests and regular operation. In recent decades, the rapid development of laser measurement technology has provided powerful methods for a variety of measuring tasks. Despite these recent developments, the use of lasers for measuring has been limited to sites provided with stationary conditions. This paper explains the elimination of pseudo-vibration and measurement noise inherent in the non-stationary conditions of the site. Upon removal of the noise, fatigue of the different structural elements of the powerhouse could be identified if significant changes over time are observed in the eigenfrequencies. The use of laser technology is to complement the regular monitoring activities on large dams, since observation and analysis of integrity parameters provide indispensable information for decision making and maintaining good structural health of ageing dams.
Highlights
Every year about 200 new large dams of different types are built worldwide; the intensity of dam construction was even greater in the past, the majority of the dams that will operate in the 21st century already exist [1]
This paper presents the first application of the Laser Doppler Vibrometer (LDV) in non-stationary conditions within a hydropower plant powerhouse
In this paper we present a methodology on how the laser Doppler vibrometer can be used inside a hydropower plant to measure vibration, while the instrument is excited as well
Summary
Every year about 200 new large dams of different types are built worldwide; the intensity of dam construction was even greater in the past, the majority of the dams that will operate in the 21st century already exist [1]. Hydroelectricity has a significant role, while hydropower turbines provide ancillary services for the electrical network: maintenance of the system frequency (due to fast and automatic response), fast reserve, reactive power series, and black-start capabilities [3]. In the past only a few units were sacrificed to be highly flexible in operation, while nowadays due to the changed conditions practically all hydro units in operation on the grid are continuously regulated and daily operate in transient and unsteady modes [5]. This sacrifice is already recognized in more frequent down times of turbines [6,7]. Goyal et al concluded from laboratory testing that each start and stop procedure causes a fatigue damage equal to 15–20 h of regular operation [8]
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