Les Cèdres
Plant size - 135 MW
Publication: presented at HydroVision 2008 (PDF format ~ 445kb)

Les Cèdres powerplant is situated on the St-Lawrence. The geometry of the water intake of each of its 17 units corresponds well to the typical shape for which the ASFM was developed: short and irregular.  The intake comprises three separate entrances, each of which are divided in two vertical sections by a two foot thick horizontal pier. 

In 2000, measurements were done using both the current meters and the ASFM.  The instruments were placed in the gate slots upstream of the trash racks. The current meter measurements were made using mobile frames, with ten current meters mounted on the lower horizontal support rod of each frame. The first set of measurements with the ASFM  was made in the same slots as the current meter frames, upstream of the trash racks.  As a result the current meter and ASFM measurements were not done simultaneously.

The second set of ASFM measurements was made with the transducers installed downstream of the trash racks in the lower headgate slots.  This was done as the measurements made upstream of the trash racks showed very low turbulence levels over a large part of the measurement section.

A comparison of the discharge measurements was made by using an index measurement as the reference since the current meter and ASFM measurements were not done at the same time. The index measurement was based on the pressure difference between the headrace level and the pressure in the scroll case and calibrated using the current meter discharge. The mean difference between current meter and the second ASFM results was 1.75 %, well within the measurement uncertainty of the current meter measurements.

Coteau 1 spillway
Publication: presented at HydroVision 2008 (PDF format ~ 445kb)

The Coteau 1 spillway is part of the Beauharnois development on the St-Lawrence river.  It is used to control the flow going to Les Cèdres powerplant situated slightly downstream. Model tests were performed to determine the spillway flow, however, a better accuracy was required for the plant operation.

The Coteau 1 spillway has twenty gates that are 12.8m wide and have an upstream water level of 5.4 m above the sill.  In 2000, Hydro-Quebec chose the ASFM method, after at first considering the use of the current meter method.  The latter was not retained as the water velocity was too high and the flow strongly inclined. 


The ASFM transducers were installed on rails specifically fabricated for the tests and could be positioned at any chosen height using two electronically synchronised hoists.  During the tests, the measurements were made while a continuous sweep of the gate section was performed with the transducers. 

The measurements were attempted at heights between the full opening and 0.55m above the sill. Beyond 0.75m above the sill, air was entrained in the flow and resulted in signal loss and a reduction in the quality index of the acoustic signal.   Only at the 0.55m position were the results satisfactory.  The measured flow of 47.0 m3/s compared well with the model test value of 46.0 m3/s (a 2.1% difference).


Rapides-des-Quinze
Plant size - 95 MW
Publication: presented at HydroVision 2008 (PDF format ~ 445kb)

Rapides-des-Quinze is not a typical low-head power plant because the two intake bays converge to a single penstock and a standard scroll case. As most of the Gibson pressure taps were blocked, the current meter method was used in the intake. In 2002, the  current meter frames were placed in the stop log slots, upstream of the trash racks. As the ASFM transducers were placed on top of the frames, they were also upstream of the trash racks.
As expected, poor results were obtained from the ASFM measurement. A very low quality index, or even no velocity were measured due to the absence of trash rack generated turbulence.




La Grande-1
Plant size - 1436 MW
Publication: presented at HydroVision 2008 (PDF format ~ 445kb)

For the 2003 comparison between the current meter and ASFM discharge measurements at La Grande-1, the ASFM transducers were mounted at the top of the current meter frame, so the velocity profile was only partially sampled. The results showed a difference between the two methods of around 1.8 %, with the ASFM underestimating. By using filtering technique to account for vibration of the frame and by changing the number of samples for each individual velocity calculation, this difference was reduced to less than 0.5 %. CFD simulations of the flow in the intake showed significant velocity variation due to the wake of the main structural members of the trash racks. This was confirmed by both the ASFM and current meter methods.



Rocher-de Grand-Mère
Plant size - 220 MW
Publication: presented at HydroVision 2008 (PDF format ~ 445kb)

The Rocher-de-Grand-Mère is a newly commissioned power plant on the St-Maurice river. The intake has two bays and the layout is typical of a modern design with a relatively smooth converging form. The discharge measurement method used for the acceptance test in 2006 was the current meter method, with 28 current meters mounted on each movable frame. The ASFM transducers were mounted near the bottom upstream edge of each end plate, around 30 cm above the lower row of current meters.



Overall, the mean difference between the CM and ASFM discharge was very low. However, large differences were observed in the left and right bay. The analysis of the velocity profile from the current meter measurements showed evidence of asymmetry with more velocity on one side of these bays. This is due to flow in the forebay arriving at a 50° angle to the intake face.

Note:
While the first measurement by a particular owner is typically carried out by AQFlow technical personnel, the user-friendly features of the ASFM offer the owners the choice of having the subsequent measurements carried out by AQFlow personnel (indicated above in italics) or by their own personnel (indicated by non-italics).

As shown, Nova Scotia Power, Hydro Québec, Korea Water Resources, Electricité de France and Douglas County PUD have all opted for having their personnel trained by AQFlow technicians as part of the first project, purchasing the ASFM and performing all subsequent measurements in-house successfully and cost-effectively.