In-Situ Measuring Campaign at the Hydropower Plant ‘‘Perućica’’, Montenegro - Part 1: Open Channel System - page 4

 

 

Overall error estimation for Diver measurement points:

Δtotal = Δdiver + Δbaro-diver + Δhand-held gauge + Δref.point2- ref.point1 + Δref.point1-ref.Sea.Level

Δdiver = 0.1% full scale (10m) = 1 [cm]

Δbaro-diver = 0.1% full scale (10m) = 1 [cm]

Δhand-held gauge = 0.5 [cm]

Δref.point2- ref.point1 = 0.5 [cm]

Δref.point1-ref.Sea.Level = 0.5 [cm]

Provided that all the errors are in the same direction, so that all the particular errors are positive ("+") or that all are negative ("-"), the overall error would reach the value of Δtotal = 3.5 cm. Since in most cases a proper distribution of points (around the exact measurement value) occurs, the expected error is calculated by applying the rules of Gauss's normal distribution and standard deviation for calculating errors.

The sum of errors Δref.point1-ref.Sea.Level and Δref.point2- ref.point1

represents an error in defining the elevation, and its maximum is 1 [cm]; their influence on the overall error is Δconst = 1 [cm].

Errors Δdiver, Δbaro-diver and Δhand-held gauge behave according to the normal distribution; their influence on the overall error is:

For-1

Max. expected error: Δ = Δconst + Δvary = 1 + 1.5 = 2.5 [cm].

An Ultrasonic E+H level sensor with data acquisition E+H minilog B was used at one measurement point (Figure 1, point 8.1). The ultrasonic sensor was placed above the water surface (Figure 5).

 

05

Figure 5: An ultrasonic level meter measurement point in the channel

 

The overall error estimation for the measurement point where an ultrasonic level meter was used (8.3):

Δtotal = ΔUS + Δhand-held gauge + Δref.point2-ref.point1 + Δref.point1-ref.Sea.Level

Δus = 2 [mm] = 0.2 [cm]

Δhand-held gauge = 0.5 [cm]

Δref.point2- ref.point1 = 0.5 [cm]

Δref.point1-ref.Sea.Level = 0.5 [cm]

Δmm = 8 [mm] = 0.8 [cm] /error caused by logger device; its value is 0.1% f.s.

Provided that all the errors are in the same direction, so that all the particular errors are positive ("+") or that all are negative ("-"), the overall error would reach the value of Δtotal = 2.5 cm. Since in most cases a proper distribution of points (around the exact measurement value) occurs, the expected error is calculated by applying the rules of Gauss's normal distribution and standard deviation for calculating errors.

The sum of errors Δref.point1-ref.Sea.Level and Δref.point2-ref.point1 represents an error in defining the elevation, and its maximum is 1 [cm]; their influence on the overall error is Δconst = 1 [cm].

Errors ΔUS, Δhand-held gauge and Δmm behave according to the normal distribution; their influence on the overall error is:

For-2

Max. expected error: Δ = Δconst + Δvary = 1 + 0.96 = 1.96 [cm]

Gate position

The use of existing equipment to mark the gate position (Figure 6) was planned, but in the case of the Krupac dam this was not possible (Figure 7).

 

 06

Figure 6: Display of the segment gate at Slano dam

 07

Figure 7: Operating wheel of the needle valve with the destroyed scale at Krupac dam