Wind resources at Horns Rev

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1.3 Quality control
Visual inspection
Once a month, the wind data are inspected visually, the data series are plotted with a
data validating tool kit, and quality codes are directly written into the database.
Data screening
In addition to the visual inspection of the data, which is conducted when new data are
collected, a screening procedure has been developed to identify data, which could be
faulty. This procedure is used to verify the data quality of huge amounts of
measurements. Typically these measurements are stored as statistic values (mean (μ),
standard deviation (σ), maximum and minimum values), where each set of values
represents a period of ten minutes:
The data screening procedure is performed in 3 steps:
1) Determination of spikes
2) Determination of drop-outs
3) Determination of periods with stationarity
One reading is defined as one single value (mean, standard deviation, maximum, or
minimum) representing one 10-min period. All readings are marked with a code = 0
from the start and a spike, a drop-out, or stationarity indication, which gives a new code
value according to the code numbers listed below.
1.3.1 Determination of spikes
Table 1.1 Definition of quality codes
Code Item
0 The reading is not validated
1 The reading is validated
2 The reading contains a spike
3 The reading contains a drop-out
4 -
5 -
9 The reading is faulty
A spike is defined as an abnormal deviation from the recorded mean value. For this
procedure four statistical values (mean, standard deviation, minimum and maximum)
are used.
A spike occurs if:
(1) |maximum-μ| > 4 × σ or
(2) |μ-minimum| > 4 × σ
Report no.: D-160949
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